14 Apr 08:42
by Dongdong Zhang,
Xiaozeng Song,
Alexander J. Gillett,
Bluebell H. Drummond,
Saul T. E. Jones,
Guomeng Li,
Hanqing He,
Minghan Cai,
Dan Credgington,
Lian Duan
Multiple donor–acceptor‐type carbazole–benzonitrile derivatives with both linear donor–π–donor and acceptor–π–acceptor structures to promote triplet upconversion are utilized as a sensitizer, realizing organic light‐emitting diodes with deep‐blue narrow‐band emission, maximum external quantum efficiency of 32.5%, and a T80 (time to 80% of the initial luminance) of >3000 h at an initial luminance of 100 cd m−2 simultaneously.
Abstract
Multiple donor–acceptor‐type carbazole–benzonitrile derivatives that exhibit thermally activated delayed fluorescence (TADF) are the state of the art in efficiency and stability in sky‐blue organic light‐emitting diodes. However, such a motif still suffers from low reverse intersystem crossing rates (k
RISC) with emission peaks <470 nm. Here, a weak acceptor of cyanophenyl is adopted to replace the stronger cyano one to construct blue emitters with multiple donors and acceptors. Both linear donor–π–donor and acceptor–π–acceptor structures are observed to facilitate delocalized excited states for enhanced mixing between charge‐transfer and locally excited states. Consequently, a high k
RISC of 2.36 × 106 s−1 with an emission peak of 456 nm and a maximum external quantum efficiency of 22.8% is achieved. When utilizing this material to sensitize a blue multiple‐resonance TADF emitter, the corresponding device simultaneously realizes a maximum external quantum efficiency of 32.5%, CIE
y
≈ 0.12, a full width at half maximum of 29 nm, and a T80 (time to 80% of the initial luminance) of > 60 h at an initial luminance of 1000 cd m−2.
03 Apr 07:58
by Scott T. Keene,
Tom P. A. Pol,
Dante Zakhidov,
Christ H. L. Weijtens,
René A. J. Janssen,
Alberto Salleo,
Yoeri Burgt
Amine‐based molecular de‐dopants enable enhancement‐mode PEDOT:PSS organic electrochemical transistors while retaining high specific capacitance and electronic mobilities. These amine de‐dopants react as both a Brønsted–Lowry base and an electron donor, lowering the effective doping by sulfonate groups and reducing the number of free electronic charge carriers in the pristine film, respectively.
Abstract
Organic electrochemical transistors (OECTs) show great promise for flexible, low‐cost, and low‐voltage sensors for aqueous solutions. The majority of OECT devices are made using the polymer blend poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), in which PEDOT is intrinsically doped due to inclusion of PSS. Because of this intrinsic doping, PEDOT:PSS OECTs generally operate in depletion mode, which results in a higher power consumption and limits stability. Here, a straightforward method to de‐dope PEDOT:PSS using commercially available amine‐based molecular de‐dopants to achieve stable enhancement‐mode OECTs is presented. The enhancement‐mode OECTs show mobilities near that of pristine PEDOT:PSS (≈2 cm2 V−1 s−1) with stable operation over 1000 on/off cycles. The electron and proton exchange among PEDOT, PSS, and the molecular de‐dopants are characterized to reveal the underlying chemical mechanism of the threshold voltage shift to negative voltages. Finally, the effect of the de‐doping on the microstructure of the spin‐cast PEDOT:PSS films is investigated.
03 Apr 07:58
by Noah Strobel,
Nikolaos Droseros,
Wolfgang Köntges,
Mervin Seiberlich,
Manuel Pietsch,
Stefan Schlisske,
Felix Lindheimer,
Rasmus R. Schröder,
Uli Lemmer,
Martin Pfannmöller,
Natalie Banerji,
Gerardo Hernandez‐Sosa
Color‐selective organic photodiodes are inkjet printed using a novel photoactive material system based on nonfullerene acceptors. This material system simplifies process development and at the same time enables a high degree of color tunability. Energetic and morphological properties are investigated and the color‐selective devices are employed in a multichannel visible‐light‐communication system.
Abstract
Future lightweight, flexible, and wearable electronics will employ visible‐light‐communication schemes to interact within indoor environments. Organic photodiodes are particularly well suited for such technologies as they enable chemically tailored optoelectronic performance and fabrication by printing techniques on thin and flexible substrates. However, previous methods have failed to address versatile functionality regarding wavelength selectivity without increasing fabrication complexity. This work introduces a general solution for printing wavelength‐selective bulk‐heterojunction photodetectors through engineering of the ink formulation. Nonfullerene acceptors are incorporated in a transparent polymer donor matrix to narrow and tune the response in the visible range without optical filters or light‐management techniques. This approach effectively decouples the optical response from the viscoelastic ink properties, simplifying process development. A thorough morphological and spectroscopic investigation finds excellent charge‐carrier dynamics enabling state‐of‐the‐art responsivities >102 mA W−1 and cutoff frequencies >1.5 MHz. Finally, the color selectivity and high performance are demonstrated in a filterless visible‐light‐communication system capable of demultiplexing intermixed optical signals.
03 Apr 07:57
by Yong Cui,
Huifeng Yao,
Jianqi Zhang,
Kaihu Xian,
Tao Zhang,
Ling Hong,
Yuming Wang,
Ye Xu,
Kangqiao Ma,
Cunbin An,
Chang He,
Zhixiang Wei,
Feng Gao,
Jianhui Hou
By finely optimizing the alkyl chains, the nonfullerene acceptor named BTP‐eC9 is synthesized and a maximum power conversion efficiency of 17.8% in organic photovoltaic cells is recorded. This work demonstrates that the optimization of alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.
Abstract
Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP‐4Cl‐BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n‐undecyl is shortened at the edge of BTP‐eC11 to n‐nonyl and n‐heptyl. As a result, the NFAs of BTP‐eC9 and BTP‐eC7 are synthesized. The BTP‐eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP‐eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP‐eC11. Significantly, due to the simultaneously enhanced short‐circuit current density and fill factor, the BTP‐eC9‐based single‐junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.
03 Apr 07:57
by Yong Cui,
Huifeng Yao,
Jianqi Zhang,
Kaihu Xian,
Tao Zhang,
Ling Hong,
Yuming Wang,
Ye Xu,
Kangqiao Ma,
Cunbin An,
Chang He,
Zhixiang Wei,
Feng Gao,
Jianhui Hou
By finely optimizing the alkyl chains, the nonfullerene acceptor named BTP‐eC9 is synthesized and a maximum power conversion efficiency of 17.8% in organic photovoltaic cells is recorded. This work demonstrates that the optimization of alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving photovoltaic performance.
Abstract
Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP‐4Cl‐BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n ‐undecyl is shortened at the edge of BTP‐eC11 to n ‐nonyl and n ‐heptyl. As a result, the NFAs of BTP‐eC9 and BTP‐eC7 are synthesized. The BTP‐eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP‐eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP‐eC11. Significantly, due to the simultaneously enhanced short‐circuit current density and fill factor, the BTP‐eC9‐based single‐junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.
09 Mar 14:40
by Jinwook Kim,
Dan Ouyang,
Haifei Lu,
Fei Ye,
Yuwei Guo,
Ni Zhao,
Wallace C. H. Choy
A novel one‐step multifunctional chemical approach is demonstrated to realize a silver nanonetwork‐based flexible transparent electrode through simultaneously controlling the Ag nanowires welding, eliminating the insulating surfactants, and improving the electrical contacts with adjacent layers. Highly performing flexible organic solar cells are achieved by the ultrasmooth surface and unprecedented stability simultaneously under electrical bias and mechanical bending.
Abstract
For ideal flexible transparent electrodes, the features of good electrical/optical properties, low surface roughness, efficient charge transportation, robust electrical stability under simultaneously continuous operation bias, and mechanical bending are critical. Herein, a flexible transparent electrode fulfilling all these features is demonstrated by silver (Ag) nanonetwork composites semi‐embedded in low‐temperature‐processed colorless polyimide (cPI), which shows a figure of merit over 1000 (5.4 Ω sq−1 sheet resistance and >94% diffused transmission at 550 nm wavelength), extremely smooth topography (<1 nm root‐mean‐square roughness and <3 nm peak‐to‐valley roughness), remarkable bending stability under continuous operation bias, and increased work function favoring the band alignment with typical charge transport layers for efficient devices. These characteristics are attributed to one‐step multifunctional chemical treatment on the composite of Ag nanowires and an example polymer of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The strategic one‐step process simultaneously offers selective welding at nanowires cross junctions to form an Ag nanonetwork, and removing polyvinylpyrrolidone surfactant from Ag nanowires and PSS from PEDOT:PSS. The flexible electrode also favors the residue‐free cPI transfer for applications. Flexible organic solar cells (OSCs) made from the electrode achieve an averaged power conversion efficiency of 14.46% (best, 15.12%), which is the best flexible OSCs reported so far.
09 Mar 12:12
by Xiaobin Chen,
Guiying Xu,
Guang Zeng,
Hongwei Gu,
Haiyang Chen,
Haitao Xu,
Huifeng Yao,
Yaowen Li,
Jianhui Hou,
Yongfang Li
A “welding” transparent flexible electrode, with respect to both the upper electrode and the underlying substrate, for fabricating high‐performance flexible OSCs is proposed, resulting in a record power conversion efficiency of single‐junction flexible organic solar cells (OSCs) with excellent mechanical properties.
Abstract
The power conversion efficiencies (PCEs) of flexible organic solar cells (OSCs) still lag behind those of rigid devices and their mechanical stability is unable to meet the needs of flexible electronics at present due to the lack of a high‐performance flexible transparent electrode (FTE). Here, a so‐called “welding” concept is proposed to design an FTE with tight binding of the upper electrode and the underlying substrate. The upper electrode consisting of solution‐processed Al‐doped ZnO (AZO) and silver nanowire (AgNW) network is well welded by utilizing the capillary force effect and secondary growth of AZO, leading to a reduction of the AgNWs junction site resistance. Meanwhile, the poly(ethylene terephthalate) is modified by embedding the AgNWs, which are then used to link with the AgNWs in the upper hybrid electrode, thus enhancing the adhesion of the electrode to the substrate. By this welding strategy, critical bottleneck issues relating to the FTEs in terms of optoelectronic and mechanical properties are comprehensively addressed. The single‐junction flexible OSCs based on this welded FTE show a high performance, achieving a record high PCE of 15.21%. In addition, the PCEs of the flexible OSCs are less influenced by the device area and display robust bending durability even under extreme test conditions.
09 Mar 11:47
by Xiaoyan Du,
Thomas Heumueller,
Wolfgang Gruber,
Osbel Almora,
Andrej Classen,
Jianfei Qu,
Feng He,
Tobias Unruh,
Ning Li,
Christoph J. Brabec
Fill factor losses in nonfullerene‐acceptor‐based organic solar cells under illumination are caused by morphological traps due to diffusion limited aggregation of nonfullerene acceptors in the mixed matrix. To achieve stable and high‐performance organic solar cells under illumination, it is essential to engineer the mixed regions from both thin film formation kinetics and materials intrinsic properties, e.g., materials compatibility and diffusion constant.
Abstract
As the power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed the 17% baseline, the long‐term stability of highly efficient OSCs is essential for the practical application of this photovoltaic technology. Here, the photostability and possible degradation mechanisms of three state‐of‐the‐art polymer donors with a commonly used nonfullerene acceptor (NFA), IT‐4F, are investigated. The active‐layer materials show excellent intrinsic photostability. The initial morphology, in particular the mixed region, causes degradation predominantly in the fill factor (FF) under illumination. Electron traps are formed due to the reorganization of polymers and diffusion‐limited aggregation of NFAs to assemble small isolated acceptor domains under illumination. These electron traps lead to losses mainly in FF, which is in contradistinction to the degradation mechanisms observed for fullerene‐based OSCs. Control of the composition of NFAs close to the thermodynamic equilibrium limit while keeping adequate electron percolation and improving the initial polymer and NFA ordering are of the essence to stabilize the FF in NFA‐based solar cells, which may be the key tactics to develop next‐generation OSCs with high efficiency as well as excellent stability.
04 Mar 13:16
by Finn Babbe,
Carolin M. Sutter‐Fella
This review summarizes the advances in the field of halide perovskites making use of optical in situ photoluminescence and UV‐vis measurements to investigate dynamic processes including synthesis, ionic movement, degradation, and phase changes.
Abstract
Halide perovskites have emerged as materials for high‐performance optoelectronic devices. Often, progress made to date in terms of higher efficiency and stability is based on increasing material complexity, i.e., formation of multicomponent halide perovskites with multiple cations and anions. In this review article, the use of in situ optical methods, namely, photoluminescence (PL) and UV‐vis, that provide access to the relevant time and length scales to ascertain chemistry–property relationships by monitoring evolving properties is discussed. Additionally, because halide perovskites are electron/ion conductors and prone to solid‐state ion transport under various external stimuli, application of these optical methods in the context of ionic movement is described to reveal mechanistic insights. Finally, examples of using in situ PL and UV‐vis to study degradation and phase transitions are reviewed to demonstrate the wealth of information that can be obtained regarding many different aspects of ongoing research activities in the field of halide perovskites.
04 Mar 09:39
by Zheng He,
Linlin Zhao,
Qiang Zhang,
Meijia Chang,
Chenxi Li,
Hesheng Zhang,
Yan Lu,
Yongsheng Chen
A simple yet general strategy is proposed to develop sensitizing agents for effective near‐infrared‐triggered dual phototherapy of cancer based on an acceptor–donor–acceptor structured small molecule. The biocompatible nanoparticles, FA‐CNPs, present high photothermal conversion efficiency (PCE = 36.5%) and efficient 1O2 generation capacity (Φ = 18.6%) under single 808 nm laser irradiation.
Abstract
Dual phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is regarded as a more effective method for cancer treatment than single PDT or PTT. However, development of single component and near‐infrared (NIR) triggered agents for efficient dual phototherapy remains a challenge. Herein, a simple strategy to develop dual‐functional small‐molecules‐based photosensitizers for combined PDT and PTT treatment is proposed through: 1) finely modulating HOMO–LUMO energy levels to regulate the intersystem crossing (ISC) process for effective singlet oxygen (1O2) generation for PDT; 2) effectively inhibiting fluorescence via strong intramolecular charge transfer (ICT) to maximize the conversion of photo energy to heat for PTT or ISC process for PDT. An acceptor–donor–acceptor (A‐D‐A) structured small molecule (CPDT) is designed and synthesized. The biocompatible nanoparticles, FA‐CNPs, prepared by encapsulating CPDT directly with a folate functionalized amphipathic copolymer, present strong NIR absorption, robust photostability, cancer cell targeting, high photothermal conversion efficiency as well as efficient 1O2 generation under single 808 nm laser irradiation. Furthermore, synergistic PDT and PTT effects of FA‐CNPs in vivo are demonstrated by significant inhibition of tumor growth. The proposed strategy may provide a new approach to reasonably design and develop safe and efficient photosensitizers for dual phototherapy against cancer.
04 Mar 09:33
by Wei Song,
Billy Fanady,
Ruixiang Peng,
Ling Hong,
Lirong Wu,
Wenxia Zhang,
Tingting Yan,
Tao Wu,
Sanhui Chen,
Ziyi Ge
Folding‐flexible semitransparent organic solar cells with over 10% efficiency and 21% average visible light transmission are realized by using xylitol microdoping and acid treatment on poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate transparent electrodes for supplying power and promoting plant growth in future multifunctional self‐powered greenhouses.
Abstract
Semitransparent organic solar cells (ST‐OSCs) have attracted extensive attention for their potential greenhouse applications. Conventional ST‐OSCs are typically based on indium tin oxide (ITO) electrodes which suffer from mechanical brittleness. Therefore, alternatives for ITO are required for realization of foldable‐flexible ST‐OSCs (FST‐OSCs). Herein, flexible poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes are prepared as ITO alternatives via polyhydroxy compound (xylitol) microdoping and acid treatment. As a result, flexible opaque OSCs based on PBDB‐T‐2F:Y6 photoactive system yield a high efficiency of 14.20%. The desirable optical properties of modified PEDOT:PSS electrodes in the visible light region and PBDB‐T‐2F:Y6 photoactive layer in the near‐infrared region facilitate the fabrication of FST‐OSCs with over 10% efficiency and 21% average visible light transmittance. Those FST‐OSCs also display excellent mechanical stability against bending and folding due to the xylitol doping, where over 80% of the initial efficiency can still be maintained even after 1000 folding cycles. Meanwhile, parallel comparisons between plants grown under direct sunlight with a FST‐OSCs roof and those under direct sunlight yield very similar results in terms of branch sturdiness and hypertrophic leaves. The results pave the way for realizing high‐performing FST‐OSCs based on PEDOT:PSS electrodes that could utilize visible light for plant growth and infrared light for power generation.
04 Mar 09:32
by Seung Un Ryu,
Zaheer Abbas,
Ara Cho,
HyunKyung Lee,
Chang Eun Song,
Hang Ken Lee,
Sang Kyu Lee,
Won Suk Shin,
Sang‐Jin Moon,
Taiho Park,
Hong Il Kim,
Jong‐Cheol Lee
A novel benzodithiophene (BDT)‐based small molecule (BDTID‐Cl) is used as an electron donor in small molecules solar cells (SM‐SCs). A record fill factor of 78.0% in SM‐SCs is achieved using BDTID‐Cl as a novel SM donor. In addition, a two‐terminal tandem solar cell is designed with a remarkable power conversion efficiency of 15.1% by complementary absorption of up to 1000 nm.
Abstract
Small molecules have been recently highlighted as active materials owing to their facile synthesisis method, well‐defined molecular structure, and highly reproducible performance. In particular, optimizing bulk heterojunction (BHJ) morphologies is important to achieving high performance in solution‐processable small molecule solar cells (SM‐SCs). Herein, a series of benzodithiophene‐based active materials with different halogen atoms substituted at the end‐group, are reported, as well as how these halogen atoms affect the morphology of BHJ architectures through microstructure analyses. Materials with chlorine atoms show a well‐mixed morphology and interpenetrating networks when blended with [6,6]‐phenyl‐C71‐butyric acid methyl ester, facilitating effective charge transportation. This controlled morphology helps attain excellent performance with a power conversion efficiency (PCE) of 10.5% and a highest fill factor of 78.0% without additives. In addition, it can be applied to two‐terminal (2T)‐tandem solar cells, attaining an outstanding PCE of up to 15.1% with complementary absorption in the field of the 2T‐tandem solar cells introducing the SM‐SCs. These results suggest that tailoring interactions with halogen atoms is an effective way to control BHJ architectures, thereby achieving remarkable performance in SM‐SCs.
04 Mar 09:31
J. Mater. Chem. A, 2020, 8,6501-6509
DOI: 10.1039/D0TA00047G, Communication
Han Yu, Lingeswaran Arunagiri, Lin Zhang, Jiachen Huang, Wei Ma, Jianquan Zhang, He Yan
Two isomeric perylene diimide acceptors with through-space conjugated [2.2]paracyclophane as a central core show dramatic differences in device performances.
The content of this RSS Feed (c) The Royal Society of Chemistry
04 Mar 09:21
J. Mater. Chem. A, 2020, 8,5467-5475
DOI: 10.1039/D0TA00687D, Communication
Open Access
Leiqiang Qin, Jianxia Jiang, Quanzheng Tao, Chuanfei Wang, Ingemar Persson, Mats Fahlman, Per O. Å. Persson, Lintao Hou, Johanna Rosen, Fengling Zhang
MXene based all-solution processed semitransparent flexible photovoltaic supercapacitor was fabricated by integrating the flexible organic photovoltaic with MXene as the electrode and transparent MXene supercapacitors in the vertical direction.
The content of this RSS Feed (c) The Royal Society of Chemistry
04 Mar 09:18
J. Mater. Chem. A, 2020, 8,5995-6003
DOI: 10.1039/D0TA00520G, Paper
Open Access
Shungang Liu, Wenyan Su, Xianshao Zou, Xiaoyan Du, Jiamin Cao, Nong Wang, Xingxing Shen, Xinjian Geng, Zilong Tang, Arkady Yartsev, Maojie Zhang, Wolfgang Gruber, Tobias Unruh, Ning Li, Donghong Yu, Christoph J. Brabec, Ergang Wang
Isomers of non-fullerene acceptors with pyrene as cores but fused at different positions were studied. FPIC6 possessed ∼119 nm of red-shift absorption and much higher power conversion efficiency of 11.55% as compared to its structural isomer FPIC5.
The content of this RSS Feed (c) The Royal Society of Chemistry
02 Mar 08:50
by Dan Yang†, Bing Cao‡, Volker Ko¨rstgens†, Nitin Saxena†, Nian Li†, Christoph Bilko†, Sebastian Grott†, Wei Chen†, Xinyu Jiang†, Julian Eliah Heger†, Sigrid Bernstorff¶, and Peter Mu¨ller-Buschbaum*†§
ACS Applied Energy Materials
DOI: 10.1021/acsaem.9b02290
02 Mar 08:39
by Chao Yao†, Jiajun Zhao†, Yanan Zhu†, Bin Liu†, Chaoyi Yan†, Dmitrii F. Perepichka‡, and Hong Meng*†
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b20544
02 Mar 08:38
by Yu-An Su†, Noriyuki Maebayashi‡, Hiroyuki Fujita§, Yan-Cheng Lin†, Chih-I Chen†, Wen-Chang Chen†?, Tsuyoshi Michinobu*§, Chu-Chen Chueh*†?, and Tomoya Higashihara*‡
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b22531
02 Mar 08:35
by Hannah L. Smith,
Jordan T. Dull,
Elena Longhi,
Stephen Barlow,
Barry P. Rand,
Seth R. Marder,
Antoine Kahn
The n‐dopant [RuCp*Mes]2 is incorporated into the polymer F8BT via solution processing. Successful n‐doping is verified using photoelectron spectroscopy and conductivity measurements. The doped F8BT film is used as an electron‐transport layer in green organic light‐emitting diodes, allowing good electron injection and high luminance and external quantum efficiency.
Abstract
n‐Doping electron‐transport layers (ETLs) increases their conductivity and improves electron injection into organic light‐emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n‐doping has been notoriously more difficult for these materials. In this work, n‐doping of the polymer poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,7‐diyl)] (F8BT) is demonstrated via solution processing, using the air‐stable n‐dopant (pentamethylcyclopentadienyl)(1,3,5‐trimethylbenzene)ruthenium dimer [RuCp*Mes]2. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]2, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n‐doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]2‐doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.
02 Mar 08:09
by Xiaoyan Du,
Thomas Heumueller,
Wolfgang Gruber,
Osbel Almora,
Andrej Classen,
Jianfei Qu,
Feng He,
Tobias Unruh,
Ning Li,
Christoph J. Brabec
Fill factor losses in nonfullerene‐acceptor‐based organic solar cells under illumination are caused by morphological traps due to diffusion limited aggregation of the nonfullerene acceptors in the mixed matrix. To achieve stable and high‐performance organic solar cells under illumination, it is essential to engineer the mixed regions from both thin‐film formation kinetics and materials intrinsic properties, e.g., materials compatibility and diffusion constant.
Abstract
As the power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed the 17% baseline, the long‐term stability of highly efficient OSCs is essential for the practical application of this photovoltaic technology. Here, the photostability and possible degradation mechanisms of three state‐of‐the‐art polymer donors with a commonly used nonfullerene acceptor (NFA), IT‐4F, are investigated. The active‐layer materials show excellent intrinsic photostability. The initial morphology, in particular the mixed region, causes degradation predominantly in the fill factor (FF) under illumination. Electron traps are formed due to the reorganization of polymers and diffusion‐limited aggregation of NFAs to assemble small isolated acceptor domains under illumination. These electron traps lead to losses mainly in FF, which is in contradistinction to the degradation mechanisms observed for fullerene‐based OSCs. Control of the composition of NFAs close to the thermodynamic equilibrium limit while keeping adequate electron percolation and improving the initial polymer and NFA ordering are of the essence to stabilize the FF in NFA‐based solar cells, which may be the key tactics to develop next‐generation OSCs with high efficiency as well as excellent stability.
28 Feb 10:26
by Juncheng Liu†?, Hao Lu†?, Yahui Liu†, Jianqi Zhang‡, Cuihong Li*†, Xinjun Xu†, and Zhishan Bo*†
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b22927
28 Feb 10:25
by Jong Hwa Lee†, Jin Hyuck Heo‡, Sang Hyuk Im*‡, and O. Ok Park*†
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b22657
28 Feb 10:25
by Yansong Ge†‡, Lin Hu§, Lifu Zhang‡, Qingxia Fu‡, Guodong Xu‡, Zhi Xing‡, Liqiang Huang‡, Weihua Zhou*†‡, and Yiwang Chen*‡?
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b18095
28 Feb 10:07
by Joseph P. Thomas, Qiuyu Shi, Marwa Abd-Ellah, Lei Zhang, Nina F. Heinig, and Kam Tong Leung*
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.9b19400
28 Feb 09:49
by Ji Wan,
Lifu Zhang,
Qiannan He,
Siqi Liu,
Bin Huang,
Lei Hu,
Weihua Zhou,
Yiwang Chen
The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction active layers. Herein, a new method by fabricating pseudoplanar heterojunction ternary organic solar cells is proposed. At the same time, the alloyed acceptor is likely formed between two nonfullerene acceptors, which may be more suitable for facilitating pseudoplanar heterojunctions.
Abstract
The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction (BHJ) active layers. Due to the inappropriate distribution of donors and acceptors in the vertical direction, a new method by fabricating pseudoplanar heterojunction (PPHJ) ternary organic solar cells is proposed to better modulate the morphology of active layer. The pseudoplanar heterojunction ternary organic solar cells (P‐ternary) are fabricated by a sequential solution treatment technique, in which the donor and acceptor mixture blends are sequentially spin‐coated. As a consequence, a higher power conversion efficiency (PCE) of 14.2% is achieved with a V
oc of 0.79 V, J
sc of 25.6 mA cm−2, and fill factor (FF) of 69.8% compared with the ternary BHJ system of 13.8%. At the same time, the alloyed acceptor is likely formed between two the acceptors through a series of in‐depth explorations. This work suggests that nonfullerene alloyed acceptor may have great potential to realize effective P‐ternary organic solar cells.
刺儿, 以昇陳 and 3 others like this
28 Feb 09:42
by Zheng He,
Linlin Zhao,
Qiang Zhang,
Meijia Chang,
Chenxi Li,
Hesheng Zhang,
Yan Lu,
Yongsheng Chen
A simple yet general strategy is proposed to develop sensitizing agents for effective near‐infrared‐triggered dual phototherapy of cancer based on an acceptor–donor–acceptor structured small molecules. The biocompatible nanoparticles, FA‐CNPs, present high photothermal conversion efficiency (PCE = 36.5%) and efficient 1O2 generation capacity (Φ = 18.6%) under single 808 nm laser irradiation.
Abstract
Dual phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is regarded as a more effective method for cancer treatment than single PDT or PTT. However, development of single component and near‐infrared (NIR) triggered agents for efficient dual phototherapy remains a challenge. Herein, a simple strategy to develop dual‐functional small‐molecules‐based photosensitizers for combined PDT and PTT treatment is proposed through: 1) finely modulating HOMO–LUMO energy levels to regulate the intersystem crossing (ISC) process for effective singlet oxygen (1O2) generation for PDT; 2) effectively inhibiting fluorescence via strong intramolecular charge transfer (ICT) to maximize the conversion of photo energy to heat for PTT or ISC process for PDT. An acceptor–donor–acceptor (A‐D‐A) structured small molecule (CPDT) is designed and synthesized. The biocompatible nanoparticles, FA‐CNPs, prepared by encapsulating CPDT directly with a folate functionalized amphipathic copolymer, present strong NIR absorption, robust photostability, cancer cell targeting, high photothermal conversion efficiency as well as efficient 1O2 generation under single 808 nm laser irradiation. Furthermore, synergistic PDT and PTT effects of FA‐CNPs in vivo are demonstrated by significant inhibition of tumor growth. The proposed strategy may provide a new approach to reasonably design and develop safe and efficient photosensitizers for dual phototherapy against cancer.
28 Feb 09:32
by Jiajie Zeng,
Jingjing Guo,
Hao Liu,
Zujin Zhao,
Ben Zhong Tang
A multifunctional luminogen with delayed fluorescence can serve as emitter and host in organic light‐emitting diodes (OLEDs). As an emitter, it affords external quantum efficiencies (ηexts) of up to 20.1/24.5% for nondoped/doped OLEDs. As a host, it provides excellent ηexts of up to 26.8%/21.0% for orange phosphorescent OLEDs/hybrid warm‐white OLEDs.
Abstract
Increasing exciton utilization and reducing exciton annihilation are crucial to achieve high performance of organic light‐emitting diodes (OLEDs), which greatly depend on molecular engineering of emitters and hosts. A novel luminogen (SBF‐BP‐DMAC) is synthesized and characterized. Its crystal and electronic structures, thermal stability, electrochemical behavior, carrier transport, photoluminescence, and electroluminescence are investigated. SBF‐BP‐DMAC exhibits enhanced photoluminescence and promotes delayed fluorescence in solid state and bipolar carrier transport ability, and thus holds multifunctionality of emitter and host for OLEDs. Using SBF‐BP‐DMAC as an emitter, the nondoped OLEDs exhibit maximum electroluminescence (EL) efficiencies of 67.2 cd A−1, 65.9 lm W−1, and 20.1%, and the doped OLEDs provide maximum EL efficiencies of 79.1 cd A−1, 70.7 lm W−1, and 24.5%. A representative orange phosphor, Ir(tptpy)2acac, is doped into SBF‐BP‐DMAC for OLED fabrication, giving rise to superior EL efficiencies of 88.0 cd A−1, 108.0 lm W−1, and 26.8% for orange phosphorescent OLEDs, and forward‐viewing EL efficiencies of 69.3 cd A−1, 45.8 lm W−1, and 21.0% for two‐color hybrid warm‐white OLEDs. All of these OLEDs can retain high EL efficiencies at high luminance, with very small efficiency roll‐offs. The outstanding EL performance demonstrates the great potentials of SBF‐BP‐DMAC in practical display and lighting devices.
28 Feb 09:21
by Lulu Sun,
Wenwu Zeng,
Cong Xie,
Lin Hu,
Xinyun Dong,
Fei Qin,
Wen Wang,
Tiefeng Liu,
Xueshi Jiang,
Youyu Jiang,
Yinhua Zhou
All‐solution‐processed and printable nonfullerene organic solar cells are fabricated. All layers from the substrate to the top electrode are solution‐processed. Hydrogen molybdenum bronze is introduced to solve the charge extraction issue and the wetting issue of the top electrode (PEDOT:PSS) on a hydrophobic active layer. Efficiency over 10% (>1 cm2) is obtained for the all‐solution‐processed nonfullerene solar cells.
Abstract
All‐solution‐processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low‐cost and ubiquitous applications. However, it is still challenging to fabricate efficient all‐solution‐processed organic solar cells with a high‐performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all‐solution‐processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (HXMoO3) between the active layer and the PEDOT:PSS. The dual functions of HXMoO3 include: 1) its deep Fermi level of −5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the HXMoO3 composition during the synthesis is critical in obtaining processing orthogonality between HXMoO3 and the PEDOT:PSS. Flexible all‐solution‐processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm2, respectively.
28 Feb 09:10
by Xiaobin Chen,
Guiying Xu,
Guang Zeng,
Hongwei Gu,
Haiyang Chen,
Haitao Xu,
Huifeng Yao,
Yaowen Li,
Jianhui Hou,
Yongfang Li
A “welding” transparent flexible electrode, with respect to both the upper electrode and the underlying substrate, for fabricating high‐performance flexible OSCs is proposed, resulting in a record power conversion efficiency of single‐junction flexible organic solar cells (OSCs) with excellent mechanical properties.
Abstract
The power conversion efficiencies (PCEs) of flexible organic solar cells (OSCs) still lag behind those of rigid devices and their mechanical stability is unable to meet the needs of flexible electronics at present due to the lack of a high‐performance flexible transparent electrode (FTE). Here, a so‐called “welding” concept is proposed to design an FTE with tight binding of the upper electrode and the underlying substrate. The upper electrode consisting of solution‐processed Al‐doped ZnO (AZO) and silver nanowire (AgNW) network is well welded by utilizing the capillary force effect and secondary growth of AZO, leading to a reduction of the AgNWs junction site resistance. Meanwhile, the poly(ethylene terephthalate) is modified by embedding the AgNWs, which are then used to link with the AgNWs in the upper hybrid electrode, thus enhancing the adhesion of the electrode to the substrate. By this welding strategy, critical bottleneck issues relating to the FTEs in terms of optoelectronic and mechanical properties are comprehensively addressed. The single‐junction flexible OSCs based on this welded FTE show a high performance, achieving a record high PCE of 15.21%. In addition, the PCEs of the flexible OSCs are less influenced by the device area and display robust bending durability even under extreme test conditions.
27 Feb 09:27
by Xiaoyang Du,
Yi Yuan,
Lei Zhou,
Hui Lin,
Caijun Zheng,
Junyi Luo,
Zhenhua Chen,
Silu Tao,
Liang‐Sheng Liao
Herein, 17% efficient and stable ternary organic solar cells are realized by introducing a delayed fluorescence material 3,4‐bis(4‐(diphenylamino)phenyl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐TPDA) in a non‐fullerene system. Long‐lifetime singlet excitons on APDC‐TPDA can transfer to the polymer donor to prolong the excitons lifetime and suppress the reverse energy transfer from charge transfer state to triplet state, and then reduce the recombination energy loss of the device.
Abstract
Charge transfer state (CT) plays an important role in exciton diffusion, dissociation, and charge recombination mechanisms. Enhancing the utilization and suppressing the recombination process of CT excitons is a promising way to improve the performance of organic solar cells (OSCs). Here, an effective method is presented via introducing a delayed fluorescence (DF) emitter 3,4‐bis(4‐(diphenylamino)phenyl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐TPDA) in OSCs. The long‐lifetime singlet excitons on APDC‐TPDA can transfer to polymer donors to prolong exciton lifetime, which ensures sufficient time for diffusion and dissociation. Concurrently, the high triplet energy level (T1) of the DF material can also prevent the reverse energy transfer from CT to T1. APDC‐TPDA‐containing ternary OSCs shows a high PCE of 16.96% with a reduced recombination energy loss of 0.46 eV. It is noteworthy that the ternary OSC also exhibits superior storage stability. After 55 days of storage, the PCE of the ternary OSC still retains about 96% of its primitive state. Furthermore, this ternary strategy is efficient and universally applicable to OSCs, and positive results can be obtained in different systems with different DF emitters. These results indicate that the ternary strategy provides a new design idea to realize high performance OSCs.
宁夏, 以昇陳 and 4 others like this
