21 Aug 07:38
by Qiancheng Zhu,
Danyang Zhao,
Mingyu Cheng,
Jianqing Zhou,
Kwadwo Asare Owusu,
Liqiang Mai,
Ying Yu
A new view of supercapacitors called “integrated supercapacitors” is proposed. The electrode of the integrated supercapacitor consists of a certain positive and a negative material. A single integrated electrode can work in both positive and negative potential window. The corresponding full device shows much higher capacitance and wider potential window than traditional single type supercapacitor due to its multiple mechanisms.
Abstract
Charging times ranging from seconds to minutes with high power densities can be achieved by electrochemical capacitors in principle. Over the past few decades, the performance of supercapacitors has been greatly improved by the utilization of new materials, preparation of unique nanostructures, investigation of electrolytes, and so on. However, the discovery of the related basic theory is very limited. Herein, a new view of a supercapacitor called the “integrated supercapacitor” is proposed. The electrode of the integrated supercapacitor consists of certain positive and negative materials. With this design, a single integrated electrode can work in both the positive and negative potential windows simultaneously. Additionally, the integrated full supercapacitor device shows a much higher capacitance and wider potential window than traditional single symmetric and asymmetric supercapacitors, which results from its multiple mechanisms, including the traditional positive//positive symmetric, positive//negative asymmetric, and negative//negative symmetric full supercapacitor mechanisms.
20 Aug 12:45
by Hao Yan,
Saurav Limbu,
Xuhua Wang,
James Nightingale,
Iain Hamilton,
Jessica Wade,
Sooncheol Kwon,
Kwanghee Lee,
Ji‐Seon Kim
The use of a small amount of a novel solid‐state ionic liquid in polymer light‐emitting diodes is demonstrated to control the charge injection and balance and hence device performance. A strong electrochemical interaction between ionic liquid and light‐emitting polymer leads to desirable changes in current and luminance turn‐on voltages, efficiency roll‐off and lifetime, that are fully compatible with printing technologies.
Abstract
Charge carrier injection and transport in polymer light‐emitting diodes (PLEDs) is strongly limited by the energy level offset at organic/(in)organic interfaces and the mismatch in electron and hole mobilities. Herein, these limitations are overcome via electrochemical doping of a light‐emitting polymer. Less than 1 wt% of doping agent is enough to effectively tune charge injection and balance and hence significantly improve PLED performance. For thick single‐layer (1.2 µm) PLEDs, dramatic reductions in current and luminance turn‐on voltages (V
J = 11.6 V from 20.0 V and V
L = 12.7 V from 19.8 V with/without doping) accompanied by reduced efficiency roll‐off are observed. For thinner (<100 nm) PLEDs, electrochemical doping removes a thickness dependence on V
J and V
L, enabling homogeneous electroluminescence emission in large‐area doped devices. Such efficient charge injection and balance properties achieved in doped PLEDs are attributed to a strong electrochemical interaction between the polymer and the doping agents, which is probed by in situ electric‐field‐dependent Raman spectroscopy combined with further electrical and energetic analysis. This approach to control charge injection and balance in solution‐processed PLEDs by low electrochemical doping provides a simple yet feasible strategy for developing high‐quality and efficient lighting applications that are fully compatible with printing technologies.
20 Aug 12:23
by Tingting Yan,
Wei Song,
Jiaming Huang,
Ruixiang Peng,
Like Huang,
Ziyi Ge
High efficiencies of 16.67% (certified as 16.0%) for rigid and 14.06% for flexible organic solar cells (OSCs) are achieved by employing a PM6:Y6:PC71BM ternary system. This is a promising ternary heterojunction strategy for the development of highly efficient rigid and flexible OSCs.
Abstract
Ternary heterojunction strategies appear to be an efficient approach to improve the efficiency of organic solar cells (OSCs) through harvesting more sunlight. Ternary OSCs are fabricated by employing wide bandgap polymer donor (PM6), narrow bandgap nonfullerene acceptor (Y6), and PC71BM as the third component to tune the light absorption and morphologies of the blend films. A record power conversion efficiency (PCE) of 16.67% (certified as 16.0%) on rigid substrate is achieved in an optimized PM6:Y6:PC71BM blend ratio of 1:1:0.2. The introduction of PC71BM endows the blend with enhanced absorption in the range of 300–500 nm and optimises interpenetrating morphologies to promote photogenerated charge dissociation and extraction. More importantly, a PCE of 14.06% for flexible ITO‐free ternary OSCs is obtained based on this ternary heterojunction system, which is the highest PCE reported for flexible state‐of‐the‐art OSCs. A very promising ternary heterojunction strategy to develop highly efficient rigid and flexible OSCs is presented.
12 Aug 12:01
by Yunpeng Qin,
Shaoqing Zhang,
Ye Xu,
Long Ye,
Yi Wu,
Jingyi Kong,
Bowei Xu,
Huifeng Yao,
Harald Ade,
Jianhui Hou
A new method of depressing E
loss for nonfullerene organic solar cells (OSCs) is reported, in which a small molecular material (NRM‐1) can be selectively dispersed into the acceptor phase in the PBDB‐T:IT‐4F‐based OSC, resulting in lower Elossrad and Elossnonrad and hence significant improvement in V
OC, and under an optimal feed ratio of NRM‐1, an enhanced efficiency can be gained.
Abstract
Reducing energy loss (E
loss) is of critical importance to improving the photovoltaic performance of organic solar cells (OSCs). Although nonradiative recombination (Elossnonrad) is investigated in quite a few works, the method for modulating Elossnonrad is seldom reported. Here, a new method of depressing E
loss is reported for nonfullerene OSCs. In addition to ternary‐blend bulk heterojunction (BHJ) solar cells, it is proved that a small molecular material (NRM‐1) can be selectively dispersed into the acceptor phase in the PBDB‐T:IT‐4F‐based OSC, resulting in lower Elossrad and Elossnonrad, and hence a significant improvement in the open‐circuit voltage (V
OC); under an optimal feed ratio of NRM‐1, an enhanced power conversion efficiency can also be gained. Moreover, the role of NRM‐1 in the method is illustrated and its applicability for several other representative OSCs is validated. This work paves a new pathway to reduce the E
loss for nonfullerene OSCs.
12 Aug 11:55
by Jeongjoo Lee,
You‐Hyun Seo,
Sung‐Nam Kwon,
Do‐Hyung Kim,
Seokhoon Jang,
Hyeonwoo Jung,
Youngu Lee,
Hasitha Weerasinghe,
Taehyo Kim,
Jin Young Kim,
Doojin Vak,
Seok‐In Na
A high power conversion efficiency of 13.5% achieved with single‐junction ternary polymer solar cells based on PTB7‐Th, PC71BM, and COi8DFIC is fabricated by slot‐die coating. This work extends to the fabrication of large‐area modules, and also to roll‐to‐roll fabrication, and demonstrates the strong potential of the slot‐die coated ternary system for commercial applications.
Abstract
The record efficiency of the state‐of‐the‐art polymer solar cells (PSCs) is rapidly increasing, due to the discovery of high‐performance photoactive donor and acceptor materials. However, strong questions remain as to whether such high‐efficiency PSCs can be produced by scalable processes. This paper reports a high power conversion efficiency (PCE) of 13.5% achieved with single‐junction ternary PSCs based on PTB7‐Th, PC71BM, and COi8DFIC fabricated by slot‐die coating, which shows the highest PCE ever reported in PSCs fabricated by a scalable process. To understand the origin of the high performance of the slot‐die coated device, slot‐die coated photoactive films and devices are systematically investigated. These results indicate that the good performance of the slot‐die PSCs can be due to a favorable molecule‐structure and film‐morphology change by introducing 1,8‐diiodooctane and heat treatment, which can lead to improved charge transport with reduced carrier recombination. The optimized condition is then used for the fabrication of large‐area modules and also for roll‐to‐roll fabrication. The slot‐die coated module with 30 cm2 active‐area and roll‐to‐roll produced flexible PSC has shown 8.6% and 9.6%, respectively. These efficiencies are the highest in each category and demonstrate the strong potential of the slot‐die coated ternary system for commercial applications.
12 Aug 11:51
by Qiao He,
Munazza Shahid,
Jiaying Wu,
Xuechen Jiao,
Flurin D. Eisner,
Thomas Hodsden,
Zhuping Fei,
Thomas D. Anthopoulos,
Christopher R. McNeill,
James R. Durrant,
Martin Heeney
A novel method to synthesize an electron‐rich building block cyclopentadithienothiophene (CDTT) via a facile aromatic extension strategy is demonstrated and a promising nonfullerene small molecule acceptor (CDTTIC) is synthesized. The CDTTIC‐based as‐cast single‐junction organic solar cells exhibit efficiencies over 11% with an ultrahigh current density.
Abstract
A new method to synthesize an electron‐rich building block cyclopentadithienothiophene (9H‐thieno‐[3,2‐b]thieno[2″,3″:4′,5′]thieno[2′,3′:3,4]cyclopenta[1,2‐d]thiophene, CDTT) via a facile aromatic extension strategy is reported. By combining CDTT with 1,1‐dicyanomethylene‐3‐indanone endgroups, a promising nonfullerene small molecule acceptor (CDTTIC) is prepared. As‐cast, single‐junction nonfullerene organic solar cells based on PFBDB‐T: CDTTIC blends exhibit very high short‐circuit currents up to 26.2 mA cm−2 in combination with power conversion efficiencies over 11% without any additional processing treatments. The high photocurrent results from the near‐infrared absorption of the CDTTIC acceptor and the well‐intermixed blend morphology of polymer donor PFBDB‐T and CDTTIC. This work demonstrates a useful fused ring extension strategy and promising solar cell results, indicating the great potential of the CDTT derivatives as electron‐rich building blocks for constructing high‐performance small molecule acceptors in organic solar cells.
12 Aug 11:48
by Zhengsheng Qin,
Haikuo Gao,
Jinyu Liu,
Ke Zhou,
Jie Li,
Yangyang Dang,
Le Huang,
Huixiong Deng,
Xiaotao Zhang,
Huanli Dong,
Wenping Hu
High‐performance single‐component organic light‐emitting transistors (OLETs) are constructed based on two high‐mobility emissive organic semiconductors of 2,6‐diphenylanthracene (DPA) and 2,6‐di(2‐naphthyl) anthracene (dNaAnt). Strong and spatially controlled light emission are demonstrated with high external quantum efficiency approaching 1.61% and 1.75% for DPA‐ and dNaAnt‐based OLETs, respectively, which shows the great potential of OLETs for science and technology investigations and novel optoelectronic logic applications.
Abstract
Construction of high‐performance organic light‐emitting transistors (OLETs) remains challenging due to the limited desired organic semiconductor materials. Here, two superior high mobility emissive organic semiconductors, 2,6‐diphenylanthracene (DPA) and 2,6‐di(2‐naphthyl) anthracene (dNaAnt), are introduced into the construction of OLETs. By optimizing the device geometry for balanced ambipolar efficient charge transport and using high‐quality DPA and dNaAnt single crystals as active layers, high‐efficiency single‐component OLETs are successfully fabricated, with the demonstration of strong and spatially controlled light emission within both p‐ and n‐ conducting channels and output of high external quantum efficiency (EQE). The obtained EQE values in current devices are approaching 1.61% for DPA‐OLETs and 1.75% for dNaAnt‐based OLETs, respectively, which are the highest EQE values for single‐component OLETs in the common device configuration reported so far. Moreover, high brightnesses of 1210 and 3180 cd m−2 with current densities up to 1.3 and 8.4 kA cm−2 are also achieved for DPA‐ and dNaAnt‐based OLETs, respectively. These results demonstrate the great potential applications of high mobility emissive organic semiconductors for next‐generation rapid development of high‐performance single‐component OLETs and their related organic integrated electro‐optical devices.
Hi and -1 others like this
12 Aug 11:46
by Ling Hong,
Huifeng Yao,
Ziang Wu,
Yong Cui,
Tao Zhang,
Ye Xu,
Runnan Yu,
Qing Liao,
Bowei Gao,
Kaihu Xian,
Han Young Woo,
Ziyi Ge,
Jianhui Hou
Eco‐compatible solvent‐processed organic photovoltaic cells with over 16% power conversion efficiency are achieved via modifying the flexible alkyl chains of BTP‐4F‐8. Combining with the polymer donor T1, over 14% power conversion efficiencies are obtained not only for using several kinds of greener solvents like o‐xylene, 1,2,4‐trimethylbenzene, and tetrahydrofuran but also for 1.07 cm2 cells by the blade‐coating method.
Abstract
Recent advances in nonfullerene acceptors (NFAs) have enabled the rapid increase in power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. However, this progress is achieved using highly toxic solvents, which are not suitable for the scalable large‐area processing method, becoming one of the biggest factors hindering the mass production and commercial applications of OPVs. Therefore, it is of great importance to get good eco‐compatible processability when designing efficient OPV materials. Here, to achieve high efficiency and good processability of the NFAs in eco‐compatible solvents, the flexible alkyl chains of the highly efficient NFA BTP‐4F‐8 (also known as Y6) are modified and BTP‐4F‐12 is synthesized. Combining with the polymer donor PBDB‐TF, BTP‐4F‐12 shows the best PCE of 16.4%. Importantly, when the polymer donor PBDB‐TF is replaced by T1 with better solubility, various eco‐compatible solvents can be applied to fabricate OPV cells. Finally, over 14% efficiency is obtained with tetrahydrofuran (THF) as the processing solvent for 1.07 cm2 OPV cells by the blade‐coating method. These results indicate that the simple modification of the side chain can be used to tune the processability of active layer materials and thus make it more applicable for the mass production with environmentally benign solvents.
05 Aug 11:24
J. Mater. Chem. A, 2019, 7,19348-19354
DOI: 10.1039/C9TA06476A, Paper
Xueshan Li, Chao Li, Linglong Ye, Kangkang Weng, Huiting Fu, Hwa Sook Ryu, Donghui Wei, Xiaobo Sun, Han Young Woo, Yanming Sun
By applying a rational molecular cutting strategy to the indacenodithienothiophene (IDTT) skeleton, a novel asymmetric A–D–π–A type acceptor, TTPT-T-2F, was developed.
The content of this RSS Feed (c) The Royal Society of Chemistry
05 Aug 11:22
by Haoran Liu,
Zhi‐Xi Liu,
Shuxu Wang,
Jiang Huang,
Huanxin Ju,
Qi Chen,
Junsheng Yu,
Hongzheng Chen,
Chang‐Zhi Li
The introduction of funtional molecular self‐assembled monolayers (SAMs) atop of zinc oxide (ZnO) effectively optimizes the energetic and heterojunction properties of the organic–metal oxide interface to improve the performance and photostability of nonfullerene polymer solar cells.
Abstract
Charge events across organic–metal oxide heterointerfaces routinely occur in organic electronics, yet strongly influence their overall performance and stability. They become even more complicated and challenging for the heterojunction conditions in polymer solar cells (PSCs), especially when nonfullerene acceptors with varied energetics are employed. In this work, an effective interfacial strategy that utilizes novel small molecule self‐assembled monolayers (SAMs) is developed to improve the electronic and electric, as well as chemical properties of organic–zinc oxide (ZnO) interfaces for nonfullerene PSCs. It is revealed that the tailored SAMs with well‐controlled energy levels and molecular dipoles can effectively optimize the energetic barrier and work function (WF) of heterointerface for optimal electron extraction. In addition, the introduction of SAMs atop of ZnO facilitates not only acceptor segregation near the n‐contact interface, but also passivation of the photocatalytic activities for ZnO, to improve overall performance and photo stability of the derived nonfullerene PSCs. Overall, the methodology and structure–property relationship revealed herein would be beneficial for a wide range of hybrid electronics.
29 Jul 11:49
by Yu Xia,
Xiao Liang,
Yun Jiang,
Shaofu Wang,
Yuyang Qi,
Yumin Liu,
Li Yu,
Huai Yang,
Xing‐Zhong Zhao
Smart photovoltaic windows with distinguished electrical power generation, energy saving, and privacy protection are enabled by coupling of multiresponsive liquid crystal/polymer composite (LCPC) films and semi‐transparent perovskite solar cells (ST‐PSC). In this design, fast and stable multiresponsive LCPC films are utilized as an inside layer to control the transparency, and high‐performance ST‐PSCs as an outside layer to offer energy generation functionality.
Abstract
Smart photovoltaic windows (SPWs) are functional devices possessing the capabilities of electrical power output, energy saving, and privacy protection by managing sunlight under external stimuli and potentially applicable in the fields of energy‐saving buildings, automobiles, and switchable optoelectronics. However, long response time, low power conversion efficiency (PCE), poor stability and cycling performance, and monostimuli responsive behavior restrict their practical applications. To address these issues, high‐efficiency and reliable SPWs are demonstrated by coupling multiresponsive liquid crystal/polymer composite (LCPC) films and semi‐transparent perovskite solar cells (ST‐PSCs). In this design, fast and multiple stimuli‐responsive LCPC films are utilized as an inside layer to control the transparency of SPWs. The ST‐PSCs with competitive PCE and qualified transparency acting as an outside layer offer energy generation functionality. Benefiting from repeatable transparency transition modulated by external stimuli, a series of working modes are achieved in the SPWs providing distinguished and stable energy generation, energy saving, and privacy protection performances.
29 Jul 11:47
J. Mater. Chem. A, 2019, 7,19522-19530
DOI: 10.1039/C9TA06385D, Paper
Open Access
Birhan A. Abdulahi, Xiaoming Li, Mariza Mone, Bisrat Kiros, Zewdneh Genene, Shanlin Qiao, Renqiang Yang, Ergang Wang, Wendimagegn Mammo
Two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI were synthesized and studied in solar cells with ITIC as an acceptor.
The content of this RSS Feed (c) The Royal Society of Chemistry
29 Jul 11:45
by Junwoo Lee,
Jae Won Kim,
Sang Ah Park,
Sung Yun Son,
Kyoungwon Choi,
Woojin Lee,
Minjun Kim,
Jin Young Kim,
Taiho Park
When crosslinking and nonfullerene acceptors are introduced in organic photovoltaics, the burn‐in loss due to thermal aging and light soaking is dramatically suppressed because of the frozen morphology and high miscibility of the acceptor. The resulting crosslinked device shows 9.4% power conversion efficiency, which is the highest value reported to date for crosslinked active materials, in the first green processing approach.
Abstract
This work deals with the investigation of burn‐in loss in ternary blended organic photovoltaics (OPVs) prepared from a UV‐crosslinkable semiconducting polymer (P2FBTT‐Br) and a nonfullerene acceptor (IEICO‐4F) via a green solvent process. The synthesized P2FBTT‐Br can be crosslinked by UV irradiation for 150 s and dissolved in 2‐methylanisole due to its asymmetric structure. In OPV performance and burn‐in loss tests performed at 75 °C or AM 1.5G Sun illumination for 90 h, UV‐crosslinked devices with PC71BM show 9.2% power conversion efficiency (PCE) and better stability against burn‐in loss than pristine devices. The frozen morphology resulting from the crosslinking prevents lateral crystallization and aggregation related to morphological degradation. When IEICO‐4F is introduced in place of a fullerene‐based acceptor, the burn‐in loss due to thermal aging and light soaking is dramatically suppressed because of the frozen morphology and high miscibility of the nonfullerene acceptor (18.7% → 90.8% after 90 h at 75 °C and 37.9% → 77.5% after 90 h at AM 1.5G). The resulting crosslinked device shows 9.4% PCE (9.8% in chlorobenzene), which is the highest value reported to date for crosslinked active materials, in the first green processing approach.
29 Jul 11:42
by Lijian Zuo,
Xueliang Shi,
Weifei Fu,
Alex K.‐Y. Jen
A semitransparent photovoltaic (ST‐PV) with a tandem architecture and selective absorption in invisible regions is designed. By developing highly efficient active layers that selective absorb in the UV and near‐infrared regions and designing an appropriate interconnecting layer and transparent electrode, the resulting tandem ST‐PV device exhibits light utilization efficiency of 5.7% with averaged visible transmittance (AVT) of 52.9% and power conversion efficiency up to 10.7%.
Abstract
Semitransparent (ST) photovoltaics (PVs) with selective absorption in the UV or/and near‐infrared (NIR) range(s) and reduced energy losses, are critical for high‐efficiency solar‐window applications. Here, a high‐performance tandem ST‐PV with selected absorption in the desirable regions of the solar spectrum is demonstrated. An ultralarge‐bandgap perovskite film (FAPbBr2.43Cl0.57, E
g ≈ 2.36 eV) is first developed to fulfil efficient selective absorption in the UV region. After optimization, the corresponding ST single junction (SJ) PV exhibits an averaged transmittance (AVT) of ≈68% and an efficiency of ≈7.5%. By sequentially reducing the visible absorbing component in a low‐bandgap organic bulk‐heterojunction layer, an ST‐PV with selective absorption in the NIR is achieved with a power conversion efficiency (PCE) of 5.9% and a high AVT of 62%. The energy loss associated with the SJ ST‐PVs is further reduced with a tandem architecture, which affords a high PCE of 10.7%, an AVT of 52.91%, and a light utilization efficiency up to 5.66%. These results represent the best balance of AVT and PCE among all ST‐PVs reported so far, and this design should pave the road for solar windows of high performance.
25 Jul 09:50
J. Mater. Chem. A, 2019, 7,18889-18897
DOI: 10.1039/C9TA04789A, Paper
Chenyi Yang, Jianqi Zhang, Ningning Liang, Huifeng Yao, Zhixiang Wei, Chang He, Xiaotao Yuan, Jianhui Hou
This work discussed the effect of energy-level offset on photovoltaic performance of PBDB-TF-based non-fullerene OSCs and established a correlation between them.
The content of this RSS Feed (c) The Royal Society of Chemistry
25 Jul 09:49
J. Mater. Chem. A, 2019, 7,20274-20284
DOI: 10.1039/C9TA06311K, Paper
Gui-Zhou Yuan, Haijun Fan, Shi-Sheng Wan, Zhao Jiang, Yan-Qiang Liu, Kai-Kai Liu, Hai-Rui Bai, Xiaozhang Zhu, Jin-Liang Wang
A PCE of 12.36% is achieved through a two-dimensional halogenated thiophene side-chain strategy, which is the highest value for NF-SMAs with a fluorinated fused central core in binary organic solar cells.
The content of this RSS Feed (c) The Royal Society of Chemistry
25 Jul 09:25
by Joachim Vollbrecht,
Viktor V. Brus,
Seo‐Jin Ko,
Jaewon Lee,
Akchheta Karki,
David Xi Cao,
Kilwon Cho,
Guillermo C. Bazan,
Thuc‐Quyen Nguyen
A comprehensive analytical model capable of quantifying bimolecular, bulk and surface trap‐assisted contributions to the overall nongeminate recombination losses in organic solar cells is reported. Common techniques such as light intensity‐dependent current density–voltage characteristics, capacitance spectroscopy, and open‐circuit voltage decay yield the necessary experimental data to successfully apply this analytical model.
Abstract
In this study, a comprehensive analytical model to quantify the total nongeminate recombination losses, originating from bimolecular as well as bulk and surface trap‐assisted recombination mechanisms in nonfullerene‐based bulk heterojunction organic solar cells is developed. This proposed model is successfully employed to obtain the different contributions to the recombination current of the investigated solar cells under different illumination intensities. Additionally, the model quantitatively describes the experimentally measured open‐circuit voltage versus light intensity dependence. Most importantly, it is possible to calculate the experimental results with the same fitting parameter values from the presented model. The validity of this model is also proven by a combination of other independent, steady‐state, and transient experimental techniques. This new powerful analytical tool will enable researchers in the photovoltaic community to take into account the synergetic contribution from all relevant types of nongeminate recombination losses in different optoelectronic systems and target their analysis of recombination dynamics at any operating voltage.
25 Jul 09:25
by Yahui Liu,
Miao Li,
Jinjin Yang,
Wenyue Xue,
Shiyu Feng,
Jinsheng Song,
Zheng Tang,
Wei Ma,
Zhishan Bo
Steric hindrance of side chains is purposely introduced in the design of planar nonfullerene acceptors. Compared with IDTT2F bearing bare thiophene bridge unit, IDTCN‐C, IDTCN‐O, and IDTCN‐S with alkyl, alkoxyl, and alkylthio substituted thiophene bridge units, all display favorable face‐on orientation and strong crystallinity. An excellent power conversion efficiency of 13.28% based on PBDB‐T:IDTCN‐O is achieved without any additives or annealing treatments.
Abstract
A series of alkyl, alkoxyl, and alkylthio substituted A–π–D–π–A type nonfullerene acceptors (NFAs) IDTCN‐C, IDTCN‐O, and IDTCN‐S are designed and synthesized. The introduction of a lateral side chain at the outer position of the π bridge unit can endow the terminal moiety with a confined planar conformation due to the steric hindrance. Thus, compared with nonsubstituted NFA (IDTT2F), these acceptors tend to form favorable face‐on orientation and exhibit strong crystallinity as verified with grazing‐incidence wide‐angle X‐ray scattering measurement. Moreover, the variation of side chain can significantly change the lowest unoccupied molecular orbital (LUMO) energy level of acceptors. As state‐of‐the‐art NFAs, a power conversion efficiency of 13.28% (V
oc = 0.91 V, J
sc = 19.96 mA cm−2, and FF = 73.2%) is obtained for the as‐cast devices based on IDTCN‐O, which is among the highest value reported in literature. The excellent photovoltaic performance for IDTCN‐O can be attributed to its slightly up‐shifted LUMO level and more balanced charge transport. This research demonstrates side chain engineering is an effective way to achieve high efficiency organic solar cells.
25 Jul 09:24
by Hyojung Cha,
George Fish,
Joel Luke,
Ahmad Alraddadi,
Hyun Hwi Lee,
Weimin Zhang,
Yifan Dong,
Saurav Limbu,
Andrew Wadsworth,
Iuliana P. Maria,
Laia Francàs,
Hou Lon Sou,
Tian Du,
Ji‐Seon Kim,
Martyn A. McLachlan,
Iain McCulloch,
James R. Durrant
An energetic cascade between mixed and pure regions assists in suppressing recombination losses in nonfullerene acceptor (NFA)‐based organic solar cells. The impact of polymer–NFA blend composition upon film morphology, energetics, charge carrier recombination kinetics, and photocurrent properties is studied.
Abstract
Here, it is investigated whether an energetic cascade between mixed and pure regions assists in suppressing recombination losses in non‐fullerene acceptor (NFA)‐based organic solar cells. The impact of polymer‐NFA blend composition upon morphology, energetics, charge carrier recombination kinetics, and photocurrent properties are studied. By changing film composition, morphological structures are varied from consisting of highly intermixed polymer‐NFA phases to consisting of both intermixed and pure phase. Cyclic voltammetry is employed to investigate the impact of blend morphology upon NFA lowest unoccupied molecular orbital (LUMO) level energetics. Transient absorption spectroscopy reveals the importance of an energetic cascade between mixed and pure phases in the electron–hole dynamics in order to well separate spatially localized electron–hole pairs. Raman spectroscopy is used to investigate the origin of energetic shift of NFA LUMO levels. It appears that the increase in NFA electron affinity in pure phases relative to mixed phases is correlated with a transition from a relatively planar backbone structure of NFA in pure, aggregated phases, to a more twisted structure in molecularly mixed phases. The studies focus on addressing whether aggregation‐dependent acceptor LUMO level energetics are a general design requirement for both fullerene and NFAs, and quantifying the magnitude, origin, and impact of such energetic shifts upon device performance.
25 Jul 09:23
by Huan‐Huan Gao,
Yanna Sun,
Yao Cai,
Xiangjian Wan,
Lingxian Meng,
Xin Ke,
Shitong Li,
Yamin Zhang,
Ruoxi Xia,
Nan Zheng,
Zengqi Xie,
Chenxi Li,
Mingtao Zhang,
Hin‐Lap Yip,
Yong Cao,
Yongsheng Chen
A simple yet effective side chain modulation on the backbone for obtaining both enhanced V
oc and J
sc simultaneously is demonstrated in this work. Compared with the controlled molecule 3TT‐CIC, 3TT‐OCIC showed PCE of 13.13% with improved V
oc of 0.69 V and J
sc of 27.58 mA cm−2, and the tandem device gives an excellent efficiency of 15.72%.
Abstract
It is a great challenge to simultaneously improve the two tangled parameters, open circuit voltage (V
oc) and short circuit current density (J
sc) for organic solar cells (OSCs). Herein, such a challenge is addressed by a synergistic approach using fine‐tuning molecular backbone and morphology control simultaneously by a simple yet effective side chain modulation on the backbone of an acceptor–donor–acceptor (A–D–A)‐type acceptor. With this, two terthieno[3,2‐b]thiophene (3TT) based A–D–A‐type acceptors, 3TT‐OCIC with backbone modulation and 3TT‐CIC without such modification, are designed and synthesized. Compared with the controlled molecule 3TT‐CIC, 3TT‐OCIC shows power conversion efficiency (PCE) of 13.13% with improved V
oc of 0.69 V and J
sc of 27.58 mA cm−2, corresponding to PCE of 12.15% with V
oc of 0.65 V and J
sc of 27.04 mA cm−2 for 3TT‐CIC–based device. Furthermore, with effective near infrared absorption, 3TT‐OCIC is used as the rear subcell acceptor in a tandem device and gave an excellent PCE of 15.72%.
25 Jul 09:23
by Katie D. Rosenthal,
Michael P. Hughes,
Benjamin R. Luginbuhl,
Niva A. Ran,
Akchheta Karki,
Seo‐Jin Ko,
Huawei Hu,
Ming Wang,
Harald Ade,
Thuc‐Quyen Nguyen
This work reports a strategy that ensures the degree of nonradiative recombination can be measured accurately in low‐energetic‐offset organic photovoltaic systems and reports key observations on the relationship between the nonradiative recombination loss and properties of the donor/acceptor interface, including an observed correlation between high domain purity and high nonradiative recombination loss.
Abstract
Open‐circuit voltage (V
OC) losses in organic photovoltaics (OPVs) inhibit devices from reaching V
OC values comparable to the bandgap of the donor–acceptor blend. Specifically, nonradiative recombination losses (∆V
nr) are much greater in OPVs than in silicon or perovskite solar cells, yet the origins of this are not fully understood. To understand what makes a system have high or low loss, an investigation of the nonradiative recombination losses in a total of nine blend systems is carried out. An apparent relationship is observed between the relative domain purity of six blends and the degree of nonradiative recombination loss, where films exhibiting relatively less pure domains show lower ∆V
nr than films with higher domain purity. Additionally, it is shown that when paired with a fullerene acceptor, polymer donors which have bulky backbone units to inhibit close π–π stacking exhibit lower nonradiative recombination losses than in blends where the polymer can pack more closely. This work reports a strategy that ensures ∆V
nr can be measured accurately and reports key observations on the relationship between ∆V
nr and properties of the donor/acceptor interface.
25 Jul 09:22
by Safakath Karuthedath,
Yuliar Firdaus,
Ru‐Ze Liang,
Julien Gorenflot,
Pierre M. Beaujuge,
Thomas D. Anthopoulos,
Frédéric Laquai
Energy and charge transfer in ternary organic solar cells (OSC) are investigated by transient spectroscopy. Depending on the excitation wavelength, either exclusive charge transfer or a competition between energy and charge transfer is observed. The presence of PC71BM in the ternary OSC increases the absorption in the UV spectral region and indirectly enhances the electron mobility of ICC6 in the blend.
Abstract
Ternary organic solar cells (OSCs) are among the best‐performing organic photovoltaic devices to date, largely due to the recent development of nonfullerene acceptors. However, fullerene molecules still play an important role in ternary OSC systems, since, for reasons not well understood, they often improve the device performance, despite their lack of absorption. Here, the photophysics of a prototypical ternary small‐molecule OSC blend composed of the donor DR3, the nonfullerene acceptor ICC6, and the fullerene derivative PC71BM is studied by ultrafast spectroscopy. Surprisingly, it is found that after excitation of PC71BM, ultrafast singlet energy transfer to ICC6 competes efficiently with charge transfer. Subsequently, singlets on ICC6 undergo hole transfer to DR3, resulting in free charge generation. Interestingly, PC71BM improves indirectly the electron mobility of the ternary blend, while electrons reside predominantly in ICC6 domains as indicated by fast spectroscopy. The improved mobility facilitates charge carrier extraction, in turn leading to higher device efficiencies of the ternary compared to binary solar cells. Using the (photo)physical parameters obtained from (transient) spectroscopy and charge transport measurements, the device's current–voltage characteristics are simulated and it is demonstrated that the parameters accurately reproduce the experimentally measured device performance.
25 Jul 09:21
by Kun Li,
Yishi Wu,
Yabing Tang,
Ming‐Ao Pan,
Wei Ma,
Hongbing Fu,
Chuanlang Zhan,
Jiannian Yao
A ternary material system–enabled 16.5% efficiency fullerene‐free organic photovoltaic cell is designed with a structurally similar higher‐LUMO‐level guest nonfullerene acceptor. The homogeneous fine morphology and the π–π stacking pattern enable the two acceptors to synergize, obtaining increased open‐circuit voltage, short‐circuit current, and fill factor.
Abstract
Ternary approaches to solar cell design utilizing a small bandgap nonfullerene acceptor as the near infrared absorber to increase the short‐circuit current density always decreases the open‐circuit voltage. Herein, a highly efficient polymer solar cell with an impressive efficiency of 16.28 ± 0.20% enabled by an effective voltage‐increased ternary blended fullerene‐free material approach is reported. In this approach, the structural similarity between the host and the higher‐LUMO‐level guest enables the two acceptors to be synergized, obtaining increased open‐circuit voltage and fill factor and a small increase of short‐circuit current density. The same beneficial effects are demonstrated by using two host binary systems. The homogeneous fine film morphologies and the π–π stacking patterns of the host blend are well maintained, while larger donor and acceptor phases and increased lamellar crystallinity, increased charge mobilities, and reduced monomolecular recombination can be achieved upon addition of the guest nonfullerene acceptor. The increased charge mobilities and reduced monomolecular recombination not only contribute to the improved fill factor but also enable the best devices to be fabricated with a relatively thicker ternary blended active layer (110 vs 100 nm). This, combined with the absorption from the added guest acceptor, contribute to the increased short‐circuit current.
25 Jul 08:52
by Zhen Xu,
Fei Xie,
Jing Wang,
Heather Au,
Mike Tebyetekerwa,
Zhenyu Guo,
Shengyuan Yang,
Yong‐Sheng Hu,
Maria‐Magdalena Titirici
All‐cellulose‐based quasi‐solid‐state sodium‐ion hybrid capacitors are assembled based on hierarchically structured carbon materials inspired by multiscale building units of cellulose as well as cellulose‐based gel electrolytes. The kinetics of the electrochemical reactions inside the hybrid capacitors are studied to bridge the gap between batteries (high energy) and supercapacitors (high power).
Abstract
Na‐ion hybrid capacitors consisting of battery‐type anodes and capacitor‐style cathodes are attracting increasing attention on account of the abundance of sodium‐based resources as well as the potential to bridge the gap between batteries (high energy) and supercapacitors (high power). Herein, hierarchically structured carbon materials inspired by multiscale building units of cellulose from nature are assembled with cellulose‐based gel electrolytes into Na‐ion capacitors. Nonporous hard carbon anodes are obtained through the direct thermal pyrolysis of cellulose nanocrystals. Nitrogen‐doped carbon cathodes with a coral‐like hierarchically porous architecture are prepared via hydrothermal carbonization and activation of cellulose microfibrils. The reversible charge capacity of the anode is 256.9 mAh g−1 when operating at 0.1 A g−1 from 0 to 1.5 V versus Na+/Na, and the discharge capacitance of cathodes tested within 1.5 to 4.2 V versus Na+/Na is 212.4 F g−1 at 0.1 A g−1. Utilizing Na+ and ClO4
− as charge carriers, the energy density of the full Na‐ion capacitor with two asymmetric carbon electrodes can reach 181 Wh kg−1 at 250 W kg−1, which is one of the highest energy devices reported until now. Combined with macrocellulose‐based gel electrolytes, all‐cellulose‐based quasi‐solid‐state devices are demonstrated possessing additional advantages in terms of overall sustainability.
25 Jul 08:50
by Haohao Feng,
Xin Song,
Zhuohan Zhang,
Renyong Geng,
Jiangsheng Yu,
Linqiang Yang,
Derya Baran,
Weihua Tang
A meta‐alkoxylphenylated dithieno[3,2‐b:2′,3′‐d]pyrrol‐fused nonfullerene acceptor, featuring predominant face‐on orientation in films, enables high‐efficiency as‐cast thick organic solar cells (OSCs). Binary blends with PBDB‐T contributes to a 12.1% power conversion efficiency. Addition of 15 wt% PC71BM renders an efficiency of 14%, among the records for as‐cast single‐junction OSCs. All devices exhibit thickness insensitivity in an active layer thickness window of 82–202 nm.
Abstract
Molecular orientation and π–π stacking of nonfullerene acceptors (NFAs) determine its domain size and purity in bulk‐heterojunction blends with a polymer donor. Two novel NFAs featuring an indacenobis(dithieno[3,2‐b:2ʹ,3ʹ‐d]pyrrol) core with meta‐ or para‐alkoxyphenyl sidechains are designed and denoted as
m‐INPOIC or
p‐INPOIC, respectively. The impact of the alkoxyl group positioning on molecular orientation and photovoltaic performance of NFAs is revealed through a comparison study with the counterpart (INPIC‐4F) bearing para‐alkylphenyl sidechains. With inward constriction toward the conjugated backbone,
m‐INPOIC presents predominant face‐on orientation to promote charge transport. The as‐cast organic solar cells (OSCs) by blending
m‐INPOIC and PBDB‐T as active layers exhibit a power conversion efficiency (PCE) of 12.1%. By introducing PC71BM as the solid processing‐aid, the ternary OSCs are further optimized to deliver an impressive PCE of 14.0%, which is among the highest PCEs for as‐cast single‐junction OSCs reported in literature to date. More attractively, PBDB‐T:
m‐INPOIC:PC71BM based OSCs exhibit over 11% PCEs even with an active layer thickness over 300 nm. And the devices can retain over 95% of PCE after storage for 20 days. The outstanding tolerance to film thickness and outstanding stability of the as‐cast devices make
m‐INPOIC a promising candidate NFA for large‐scale solution‐processable OSCs.
25 Jul 08:46
by Zhiyuan Chen,
Yongrui Yang,
Zhihao Ma,
Tao Zhu,
Lei Liu,
Jie Zheng,
Xiong Gong
All‐solid‐state flexible asymmetric supercapacitors with the graphene nanoribbon/Co0.85Se composites as the positive electrode, the graphene nanoribbon/Bi2Se3 composites as the negative electrode, and the polymer‐grafted‐graphene oxide membranes as solid‐state electrolytes exhibit an operating voltage of 1.6 V, an energy density of 30.9 Wh kg−1 at the power density of 559 W kg−1, and excellent cycling stability with 89% capacitance retention after 5000 cycles.
Abstract
All‐solid‐state flexible asymmetric supercapacitors (ASCs) are developed by utilization of graphene nanoribbon (GNR)/Co0.85Se composites as the positive electrode, GNR/Bi2Se3 composites as the negative electrode, and polymer‐grafted‐graphene oxide membranes as solid‐state electrolytes. Both GNR/Co0.85Se and GNR/Bi2Se3 composite electrodes are developed by a facile one‐step hydrothermal growth method from graphene oxide nanoribbons as the nucleation framework. The GNR/Co0.85Se composite electrode exhibits a specific capacity of 76.4 mAh g−1 at a current density of 1 A g−1 and the GNR/Bi2Se3 composite electrode exhibits a specific capacity of 100.2 mAh g−1 at a current density of 0.5 A g−1. Moreover, the stretchable membrane solid‐state electrolytes exhibit superior ionic conductivity of 108.7 mS cm−1. As a result, the flexible ASCs demonstrate an operating voltage of 1.6 V, an energy density of 30.9 Wh kg−1 at the power density of 559 W kg−1, and excellent cycling stability with 89% capacitance retention after 5000 cycles. All these results demonstrate that this study provides a simple, scalable, and efficient approach to fabricate high performance flexible all‐solid‐state ASCs for energy storage.
25 Jul 08:45
by Jian Yan,
Shaohui Li,
Binbin Lan,
Yucheng Wu,
Pooi See Lee
The exploration of high‐performance nanostructured supercapacitor materials and multifunctional supercapacitors have attracting immense attention in recent years. The details on the charge–discharge mechanism of supercapacitors, developments on various structure/morphology engineering of materials, and achievements in multifunctional supercapacitors are comprehensively presented. The perspectives on the standardization of measurements and challenges of supercapacitors are also addressed.
Abstract
As an intermediate step during energy usage, supercapacitors with superior power density, long‐term cycling stability, and moderate energy density have attracted immense interest as a facile route to use energy in a clean, efficient, and versatile manner in smart grid applications, as well as portable devices and other applications. Currently, the major drawback of supercapacitors is the low energy density. Electrode materials are the key components determining the cell performance. Great research efforts are made to develop nanostructured electrode materials with high performance. On the other hand, integrating supercapacitors with other applications have led to the emergence of many new types of multifunctional supercapacitors, which are attractive for a myriad of applications. The current understanding on charge/discharge mechanisms of electric double layer capacitors and pseudo‐capacitors is discussed along with recent development in designing nanostructured electrode materials by structure/morphology engineering, doping, and crystal structure controlling. Achievements in multifunctional supercapacitors like flexible supercapacitors, all‐solid‐state supercapacitors, self‐healing supercapacitors, electrochromic supercapacitors, self‐chargeable supercapacitors, and supercapacitors integrated with sensors are illustrated. Finally, opportunities and challenges in developing high performance and multifunctional supercapacitors are proposed.
25 Jul 08:43
by Runnan Yu,
Huifeng Yao,
Yong Cui,
Ling Hong,
Chang He,
Jianhui Hou
Ternary polymer solar cells are successfully developed by combining a fullerene derivative and a nonfullerene material as acceptors. The introduction of PC61BM into the PBDB‐TF:Y6 blend effectively improves the charge transport properties and reduces the nonradiative energy loss. Ultimately, the main photovoltaic parameters are simultaneously enhanced in the ternary devices, leading to an outstanding efficiency of 16.5% (certificated as 16.2%).
Abstract
Recent advances in the material design and synthesis of nonfullerene acceptors (NFAs) have revealed a new landscape for polymer solar cells (PSCs) and have boosted the power conversion efficiencies (PCEs) to over 15%. Further improvements of the photovoltaic performance are a significant challenge in NFA‐PSCs based on binary donor:acceptor blends. In this study, ternary PSCs are fabricated by incorporating a fullerene derivative, PC61BM, into a combination of a polymer donor (PBDB‐TF) and a fused‐ring NFA (Y6) and a very high PCE of 16.5% (certified as 16.2%) is recorded. Detailed studies suggest that the loading of PC61BM into the PBDB‐TF:Y6 blend can not only enhance the electron mobility but also can increase the electroluminescence quantum efficiency, leading to balanced charge transport and reduced nonradiative energy losses simultaneously. This work suggests that utilizing the complementary advantages of fullerene and NFAs is a promising way to finely tune the detailed photovoltaic parameters and further improve the PCEs of PSCs.
25 Jul 08:42
by Ki‐Won Seo,
Jaemin Lee,
Jihwan Jo,
Changsoon Cho,
Jung‐Yong Lee
A poly(3,4‐ethylenedioxythiophene)‐free and indium tin oxide (ITO)‐free junction‐free AgNN electrode with high optoelectrical properties is proposed for flexible organic solar cells (FOSCs). The electrical sheet resistance and optical transmittance can be controlled by both initial metal thickness and NN density; even a very thin Ag layer with appropriate NN density can show high transmittance and low sheet resistance, yielding a highly efficient FOSC.
Abstract
A novel approach to fabricate flexible organic solar cells is proposed without indium tin oxide (ITO) and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using junction‐free metal nanonetworks (NNs) as transparent electrodes. The metal NNs are monolithically etched using nanoscale shadow masks, and they exhibit excellent optoelectronic performance. Furthermore, the optoelectrical properties of the NNs can be controlled by both the initial metal layer thickness and NN density. Hence, with an extremely thin silver layer, the appropriate density control of the networks can lead to high transmittance and low sheet resistance. Such NNs can be utilized for thin‐film devices without planarization by conductive materials such as PEDOT:PSS. A highly efficient flexible organic solar cell with a power conversion efficiency (PCE) of 10.6% and high device yield (93.8%) is fabricated on PEDOT‐free and ITO‐free transparent electrodes. Furthermore, the flexible solar cell retains 94.3% of the initial PCE even after 3000 bending stress tests (strain: 3.13%).
25 Jul 08:40
by Xiaopeng Xu,
Kui Feng,
Zhaozhao Bi,
Wei Ma,
Guangjun Zhang,
Qiang Peng
A platinum(II) complexation strategy is developed to regulate the crystallinity of a newly designed s‐tetrazine‐containing wide‐bandgap copolymer donor PSFTZ, and optimize the morphology of the PSFTZ:Y6 active blend film, which boosts successfully the power conversion efficiency of the resulting nonfullerene polymer solar cells (NF‐PSCs) from 13.03% to 16.35%. 16.35% is the new record for single‐junction NA‐PSCs at present.
Abstract
A new strategy of platinum(II) complexation is developed to regulate the crystallinity and molecular packing of polynitrogen heterocyclic polymers, optimize the morphology of the active blends, and improve the efficiency of the resulting nonfullerene polymer solar cells (NF‐PSCs). The newly designed s‐tetrazine (s‐TZ)‐containing copolymer of PSFTZ (4,8‐bis(5‐((2‐butyloctyl)thio)‐4‐fluorothiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐3,6‐bis(4‐octylthiophen‐2‐yl)‐1,2,4,5‐tetrazine) has a strong aggregation property, which results in serious phase separation and large domains when blending with Y6 ((2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile)), and produces a power‐conversion efficiency (PCE) of 13.03%. By adding small amount of Pt(Ph)2(DMSO)2 (Ph, phenyl and DMSO, dimethyl sulfoxide), platinum(II) complexation would occur between Pt(Ph)2(DMSO)2 and PSFTZ. The bulky benzene ring on the platinum(II) complex increases the steric hindrance along the polymer main chain, inhibits the polymer aggregation strength, regulates the phase separation, optimizes the morphology, and thus improves the efficiency to 16.35% in the resulting devices. 16.35% is the highest efficiency for single‐junction PSCs reported so far.
