by Jun Xi,
Chengcheng Piao,
Junseop Byeon,
Jungjin Yoon,
Zhaoxin Wu,
Mansoo Choi
A rational core–shell design of open air low temperature in situ processable CsPbI3 quasi‐nanocrystals is proposed. A bifunctional ligand 4‐fluorophenethylammonium iodide and new compound H2PbI4 increase crystal stability, charge extraction, and assist divalent ion doping, respectively. The best p‐i‐n solar cell with 13.4% efficiency can retain 72% beyond 500 h in ambient air without encapsulation.
Abstract
As a promising alternative, inorganic perovskite nanocrystals allow reinforced stability of photovoltaic device. Unfortunately, directly assembling these nanocrystals into film is uncontrollable. Instead, in situ assembling technology under low temperature in open air is attractive but limited due to the tendency of nonperovskite transition. The adverse shell ligands and unstable core lattices are known as the fundamental problems. In order to address this issue, here proposed is a rational core–shell design: 1) with respect to ligands, a new one, 4‐fluorophenethylammonium iodide, is used to enhance bonding force and charge coupling between ligands and nanocrystals; 2) with respect to lattices, a novel compound H2PbI4 is employed to assist divalent ion (Mn2+) doping into perovskite lattices. By low temperature in situ processing CsPbI3 quasi‐nanocrystal film, the highest power conversion efficiency of 13.4% for p‐i‐n solar cells is achieved, which retains 92% after 500 h in ambient air. The current study underlines the significance of rational hierarchical design of inorganic perovskite nanocrystals, especially for low temperature in situ processable electronic devices.
The surface defects and grain boundary defects of organometallic halide perovskite films are detrimental to both the efficiency and stability of perovskite solar cells (PSCs). Furthermore, the electrical conductivity, work function and surface morphology of the hole transport layer (HTL) can also affect the performance of PSCs significantly. Here, we first have developed a novel synergistic strategy that uses multiple functional EMIC (1-Ethyl-3-methylimidazolium chloride) ionic liquid to modify PEDOT:PSS (poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate) HTL, thereby obtaining the HTL with high electrical conductivity, low work function and smooth surface. Moreover, a novel S-acetylthiocholine chloride molecule which replaces expensive PCBM (phenyl-C61-butyric acid methyl ester) is developed to effectively passivate the negative- and positive-charged ionic defects in hybrid perovskite. The synergistic strategy extends the carrier recombination lifetime and reduces the charge trap density. In addition, the current hysteresis of the inverted device was also effectively eliminated. As a result, the champion cell in small area shows 20.06% efficiency with no hysteresis, along with an efficiency 18.77% for inverted PSCs in an active area of 1 cm2, both of which are the highest efficiency in the one-step PEDOT:PSS-based inverted PSCs so far. Compared to PCBM, the device passivated by S-acetylthiocholine chloride also has improved environmental stability (retaining 85% of initial PCE after 35 days storage without encapsulation in air with 60% humidity) and thermal stability (retaining 87% of initial PCE after 80 °C for 24 h storage without encapsulation under inert atmosphere).
Author(s): Lin Xu, Xinfu Chen, Junjie Jin, Wei Liu, Biao Dong, Xue Bai, Hongwei Song, Peter Reiss
Abstract
Perovskite solar cells (PSCs) have shown unprecedented efficiency progress from 3.8% in 2009 to 24.2% in 2019. Up to now, the highest device efficiencies were recently achieved by employing n-type SnO2 on the transparent front electrode with conventional structure (n-i-p structure), while TiO2 remains the most used electron transport layer in PSCs. However, the comparably large J-V hysteresis in planar PSCs and the high temperature process required in mesoporous TiO2 structures severely limit the further commercial application. Therefore, inverted PSCs (p-i-n structure) employing p-type NiOx as the hole transport layer (HTL) on the front electrode have attracted massive attention in recent years. This is mainly due to their lower processing temperature for large scale and flexible devices, negligible J−V hysteresis effects, and furthermore, better stability as compared to organic HTLs. In spite of all these merits of NiOx based HTLs, the reported efficiencies of inverted PSCs are still lower than that of conventional PSCs. The main reasons can be assigned to limitations arising from the low conductivity and a mismatched band position of NiOx. Doping has been considered to be an effective way to adjust the electrical and optical properties of semiconductor oxides in a large extent and has already shown promising results in improving the photovoltaic performance of NiOx based inverted PSCs. In this review, recent investigations about the influence of doping on the structural, electrical, and optical properties of NiOx HTLs are summarized. We also discuss the advantages and current challenges of utilizing NiOx HTLs in PSCs and attempt to give prognoses on future progress exploiting them in high-efficiency inverted PSCs.
Graphical abstract
Research on planar perovskite solar cells (PSCs) in (inverted) p–i–n configuration, using transparent p-type front-electrodes, is strongly emerging. NiOx has been demonstrated to be one of the most promising candidates to be employed as a hole transport layer (HTL) in these devices, however, its low intrinsic conductivity and unmatched Fermi level with respect to the perovskite layer limit the performance of the PSCs. Extrinsic doping of NiOx HTLs is a versatile and powerful strategy to mitigate these shortcomings, which, within the past three years, led to significantly enhanced power conversion efficiencies (exceeding 20%). In this review, we present a comprehensive overview of the strategies applied to improve the performance of NiOx HTLs used in inverted PSCs with special emphasis on the properties modulation induced by extrinsic doping. Current challenges and perspectives for exploiting these HTLs in high-efficiency inverted PSCs are also given.
by Yulin Cao,
Wei Chen,
Huiliang Sun,
Dong Wang,
Peng Chen,
Aleksandra B. Djurišić,
Yudong Zhu,
Bao Tu,
Xugang Guo,
Ben Zhong Tang,
Zhubing He
An aggregation‐induced emission (AIE) molecule is successfully employed as an effective hole transport material in an inverted planar perovskite solar cell. The improvement of perovskite crystallinity and the suppression of nonradiative recombination at the AIE/perovskite interface result in enhanced device performance and stability as compared with the poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS)‐based control one.
Organic hole‐transport materials (HTMs) are very promising for perovskite solar cells (PSCs) because the molecule structure is engineered via facile chemical routes. Herein, an aggregation‐induced emission (AIE) molecule, 2‐(2,7‐bis(4‐(bis(4‐methoxyphenyl)amino)phenyl)‐9H‐fluoren‐9‐ylidene)malononitrile (TFM), is successfully employed for the first time as a HTM in an inverted planar PSC, obtaining a promising device performance superior to that of the control device with poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) HTM. An optimal power conversion efficiency (PCE) of 16.03% is obtained for the TFM‐based PSCs with a Jsc of 22.68 mA cm−2, Voc of 0.97 V and FF of 72.9%, while that of the control PEDOT:PSS‐based device is 14.95%. Steady‐state and time‐resolved photoluminescence results reveal suppressed nonradiative recombination at the TFM/perovskite interface that is attributed to the effective passivation of the uncoordinated Pb at the perovskite surface by the CN− groups of TFM molecules, as confirmed by X‐ray photoelectronic spectroscopy measurements. In addition to the passivation, the hydrophobic character of TFM films also contributes to the improved device stability. The findings demonstrate the potential of AIE molecules in PSCs and also paves a novel way to improve device performance and stability by molecular structure engineering of AIE molecules in the future.
by Zhihui Zhang,
Jiawen Wu,
Sheng Li,
Shuang Liu,
Qifei Wang,
Anyi Mei,
Yaoguang Rong,
Yue Hu,
Hongwei Han
In this review, multifunctional molecules for perovskite solar cells (PSCs) are introduced. All the molecules can help to improve the performance of PSCs, such as forming low‐dimensional or dimensionally mixed perovskites and passivating defects, thus inducing good crystal growth behavior, improving the morphology of perovskite films, and facilitating charge transport. Eventually, PSCs with superior photoelectric properties and better stability can be obtained.
Organic–inorganic halide perovskite solar cells (PSCs) have recently attracted much attention with the recent certified power conversion efficiency (PCE) record exceeding 24%. To date, many approaches have been developed for producing high‐performance PSCs, in which the application of multifunctional molecules plays an important role. The multifunctional molecules can modify the morphology of perovskite films and/or passivate the surface defects through interactions with the perovskites' boundaries and/or the charge carrier extraction interfaces. As a result, both the PCEs and the stability of PSCs are improved. The recent progress in the development of multifunctional molecules‐incorporated PSCs is reviewed. The importance of further understanding of the role of the multifunctional molecules in the perovskite film formation process and defect passivation mechanism is discussed. Further research in terms of multifunctional molecules can help to develop high‐performance devices with long‐term stability for future practical applications of PSCs.
by Shihao Yuan,
Yuan Cai,
Shaomin Yang,
Huan Zhao,
Fang Qian,
Yu Han,
Jie Sun,
Zhike Liu,
Shengzhong (Frank) Liu
A simple coalloying strategy is applied to partly substitute HC(NH2)2/CH3NH3 (FA/MA) and I− in FA0.85MA0.15PbI3 perovskite by Cs+ and Ac− respectively, which is an effective way to improve the tolerance factor, crystallinity, electronic properties, and band structure of FA0.85MA0.15PbI3 materials. Consequently, the coalloyed perovskite solar cells yield a champion power conversion efficiency of 21.95% with negligible hysteresis and high stability.
A simple coalloying strategy is applied to improve the efficiency and stability of FA0.85MA0.15PbI3 perovskite solar cells (PSCs) by using cesium acetate (CsAc) as an additive. It is found that the simultaneous incorporation of cation (Cs+) and anion (Ac−) into the FA0.85MA0.15PbI3 film is an effective approach to realize lattice contraction, grain size enlargement, photoelectric properties improvement, band structure modulation, and therefore the optimization of the efficiency and stability of PSCs. At optimal CsAc alloying, the FA0.85MA0.15PbI3 PSCs achieve a maximum power conversion efficiency (PCE) of 21.95% and an average of over 21%. In addition, the alloyed PSCs retain 97% of their initial PCE values after aging for 55 days in air without encapsulation.
by Tongfa Liu,
Zheng Wang,
Lingyun Lou,
Shuang Xiao,
Shizhao Zheng,
Shihe Yang
The power conversion efficiency of the carbon‐based perovskite solar cells is enhanced by 21.4% simply by interfacial post‐treatment with cesium acetate. The nonencapsulated device can remain stable for 4 months without observable degradation. The improved performance is attributed to the better matched energy levels and the reduced defect density.
The interface between the perovskite layer and carbon electrode is important for printable carbon‐based perovskite solar cells (PSCs) to improve the power conversion efficiency (PCE) and device stability. A series of acetate salts are employed to in situ post‐modify the interface between the perovskite layer and carbon electrode for printable carbon‐based PSCs by the post‐treatment method. Cesium acetate (CsAc) is identified to enhance the average PCE from 12.6% to 15.3%. The stabilized output PCE reaches 15.6%, and the highest open‐circuit voltage (VOC) is 1.1 V, representing a new milestone in increasing the ratio of VOC/Eg (Eg: bandgap of perovskite) to be 0.67 for the printable carbon‐based PSCs without hole transporting materials. Moreover, the device stability in air is also improved by CsAc post‐modification. The improved performance is attributed to the better matching of energy levels of the perovskite layer with a carbon electrode and reduced defect density in the perovskite layer via in situ produced methylammonium acetate and ion replacement. This simple and effective CsAc post‐treatment method opens a new promising direction for developing scalable carbon‐based PSCs.
by Fengzhu Li,
Haochen Fan,
Jie Zhang,
Jin-Hua Huang,
Pengcheng Wang,
Caiyan Gao,
Lian-Ming Yang,
Zonglong Zhu,
Alex K.-Y. Jen,
Yanlin Song,
Ke-Jian Jiang
Trihydrazine dihydriodide is successfully used as an additive for solution deposition of a formamidinium tin iodide (FASnI3) perovskite layer, resulting in improved surface morphology and reduced carrier concentration. Using the derived FASnI3 layer as a light absorber, a maximum power conversion efficiency of 8.48% is achieved in a planar‐heterojunction solar cell using common precursor SnI2 with 99% purity.
The deposition of a uniform and dense tin‐based perovskite layer with low defect‐caused background carrier density is crucial for achieving efficient tin perovskite solar cells (PSCs). These defects are mainly caused by the rapid oxidation of Sn2+ to Sn4+ in tin perovskite during device fabrication. Herein, trihydrazine dihydriodide ((N2H4)3(HI)2) is used as an additive for solution deposition of a formamidinium tin iodide (FASnI3) perovskite layer. The resultant FASnI3 layer is homogeneous with full surface coverage; moreover, the content of Sn4+ is significantly reduced in the film from the SnI2 precursor owing to the reductive property of (N2H4)3(HI)2. With the high‐quality FASnI3 layer as a light absorber, planar‐heterojunction perovskite solar cells are fabricated, exhibiting a maximum power conversion efficiency of 8.48% and good reproducibility. This work opens new possibilities for achieving efficient lead‐free tin‐based perovskite solar cells.
by Cenqi Yan,
Tao Yang,
Wei Gao,
Yiqun Xiao,
Yuhao Li,
Xinhui Lu,
Chuluo Yang,
Gang Li
Three novel low‐bandgap fused‐ring electron acceptors, BPIC, BPIC‐2Cl, and BPIC‐4Cl are designed based on a heptacyclic core, using phenyl‐substituted benzo[1,2‐b:4,5‐b′]dithiophene as the central unit, end‐capped with 1,1‐dicyano methylene‐3‐indanone (INCN), mono‐chlorinated INCN, and di‐chlorinated INCN moieties, respectively. The effects of chlorination on optical and electronic properties of molecules, film morphology, and photovoltaic device performance are investigated.
A new heptacyclic core based on phenyl‐substituted benzo[1,2‐b:4,5‐b']dithiophene (BDT) is designed and paired with 1,1‐dicyano methylene‐3‐indanone (INCN) end group to construct a nonfullerene acceptor, BPIC. The strong aggregation and large phase separation in the poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))]) (PBDB‐T):BPIC blend cause inefficient exciton dissociation and ineffective charge transport, resulting in a low 11.12% power conversion efficiency (PCE) with low short‐circuit current density (JSC) and fill factor (FF). To finely control the active‐layer nanomorphology, the chlorine atom is introduced into the INCN termini, and di‐chlorinated BPIC‐2Cl and tetra‐chlorinated BPIC‐4Cl are synthesized. It is an interesting phenomenon that, unlike other literature reports, while the di‐chlorination reduces crystallinity and phase‐separation scale, further chlorination increases crystallinity and phase separation. The PBDB‐T:BPIC‐2Cl device exhibits suitable molecular packing and nearly ideal nanoscale phase separation, which facilitates exciton dissociation and charge transport and thus yields the higher PCE of 12.63% with significantly improved JSC and FF. PBDB‐T:BPIC‐4Cl device, however, exhibits strong stacking intensity and excessively large phase separation, leading to the clearly reduced JSC, FF, and PCE of only 8.23%. This work demonstrates that novel phenyl‐substituted BDT core and delicated chlorination strategy provides powerful tools for high‐performance nonfullerene acceptors in organic solar cells.
by Juanita Hidalgo,
Andrés‐Felipe Castro‐Méndez,
Juan‐Pablo Correa‐Baena
Imaging and mapping characterization techniques are used to understand the fundamental properties that allow lead halide perovskites to have excellent performance metrics. In this work, commonly‐used and specialized tools that are used characterize halide perovskite materials and solar cells, including electron microscopy, atomic force microscopy, synchrotron‐based X‐ray mapping, and ultrafast and photoluminescence mapping are reviewed.
Abstract
Perovskite solar cells (PSCs) have attracted much attention as efficiencies have gone beyond 24%. To achieve these impressive numbers, the PSC scientific community is working to improve the perovskite optoelectronic properties. Imaging and mapping characterization techniques have been widely used to understand the fundamental properties that allow lead halide perovskites to achieve high performance. In this review, these techniques are evaluated, from simple tools, such as electron microscopy, to more complex systems that include atomic force microscopy, synchrotron‐based X‐ray mapping, and ultrafast and photoluminescence mapping. These tools have helped understand lead halide perovskites and their impressive optoelectronic properties, which make them outstanding materials for solar cell applications.
by Endong Jia,
Dong Wei,
Peng Cui,
Jun Ji,
Hao Huang,
Haoran Jiang,
Shangyi Dou,
Meicheng Li,
Chunlan Zhou,
Wenjing Wang
The ferroelectric P(VDF‐TrFE) polymer dopant results in promoting the built‐in electric field in the absorber perovskite layer, which leads to both increasing the minority carrier diffusion length and reducing the nonradiative recombination loss. Compared to typical CH3NH3PbI3‐based perovskite solar cells (PSCs), optimized FE‐PSCs present higher VOCs up to 1.17 V and power conversion efficiency up to 18%.
Abstract
A novel ferroelectric coupling photovoltaic effect is reported to enhance the open‐circuit voltage (VOC) and the efficiency of CH3NH3PbI3 perovskite solar cells. A theoretical analysis demonstrates that this ferroelectric coupling effect can effectively promote charge extraction as well as suppress combination loss for an increased minority carrier lifetime. In this study, a ferroelectric polymer P(VDF‐TrFE) is introduced to the absorber layer in solar cells with a proper cocrystalline process. Piezoresponse force microscopy (PFM) is used to confirm that the P(VDF‐TrFE):CH3NH3PbI3 mixed thin films possess ferroelectricity, while the pure CH3NH3PbI3 films have no obvious PFM response. Additionally, with the applied external bias voltages on the ferroelectric films, the devices begin to show tunable photovoltaic performance, as expected for the polarization in the poling process. Furthermore, it is shown that through the ferroelectric coupled effect, the efficiency of the CH3NH3PbI3‐based perovskite photovoltaic devices is enhanced by about 30%, from 13.4% to 17.3%. And the open‐circuit voltages (VOC) reach 1.17 from 1.08 V, which is reported to be among the highest VOCs for CH3NH3PbI3‐based devices. It should be noted in particular that the thickness of the layer is less than 160 nm, which can be regarded as semi‐transparent.
Interfacial engineering strategy between the perovskite absorber and the charge transport layer play a vital role in highly efficient perovskite solar cells. Here, we propose an amorphous tungsten oxides/tin dioxide hybrid electron transport layer to effectively block holes through the pinholes and cracks of tin dioxide to indium tin oxide, resulting in promoting charge extraction and hindering electron-hole recombination process at the hetero-interface. Moreover, owing to the higher mobility of amorphous tungsten oxides and formation of cascade energy level sequence between amorphous tungsten oxides and tin dioxide, better electron transport is obtained compared with the traditional electron transport layer. The PSCs based on amorphous tungsten oxides/tin dioxide hybrid electron transport layer shows a better power conversion efficiency of 20.52% than the single tin dioxide electron transport layer. This study guides design strategies of the electron transport layer to enhance the efficiency of the perovskite solar cells by interfacial engineering. Moreover, the entire devices preparation process are finished at a temperature below 150 °C, promising great potential for the practical use in monolithic tandem devices and providing an avenue for the progress of flexible device.
Author(s): Xiaotian Hu, Xiangchuan Meng, Lin Zhang, Yanyan Zhang, Zheren Cai, Zengqi Huang, Meng Su, Yang Wang, Mingzhu Li, Fengyu Li, Xi Yao, Fuyi Wang, Wei Ma, Yiwang Chen, Yanlin Song
Context & Scale
PSCs have become promising candidates for a flexible solar power source because of flexible, lightweight features and excellent photovoltaic efficiency. However, there is a huge gap in efficiency when compared with the rigid devices. The lack of an appropriate transparent electrode to replace the fragile PET/ITO is the Achilles’ heel of flexible PSCs.
Here, we report a conductive and robust network electrode to generally address the performance disparity of flexible PSCs. With the assists of the ionic additive and solution shearing during slot-die printing, a desired network structure of conductive polymer is achieved. The network PEDOT:PSS electrode synchronously satisfies high conductivity, high transmittance, and excellent flexibility for flexible PSCs. We also demonstrate the viability of this electrode for large-area reproducibility and diversity. This approach will open a general protocol for fabricating flexible photoelectronic devices.
Summary
Lightweight and mechanically flexible photovoltaics enable roll-to-roll processing, which improves their potential for low-cost mass production. However, the lack of highly conductive and transparent flexible electrodes still causes reduced efficiency relative to solar cells formed on rigid substrates. Here, we demonstrate an electrode that reduces this performance gap in perovskite solar cells (PSCs) by regulating the phase separation of a conducting polymer network using a fluorosurfactant dopant. This network electrode simultaneously offers high conductivity (>4,000 S/cm), improved transmittance (over 80% from 400 to 900 nm), and high mechanical endurance. PSCs with this electrode achieve stabilized power conversion efficiencies of 19.0% and 10.9% at aperture areas of 0.1 cm2 and 25 cm2, respectively, which is comparable to control devices on rigid substrates. This electrode further shows promise as the top electrode in semi-transparent PSCs, which show a stabilized efficiency of 12.5% at 30.6% average visible transmittance. Each of these cells exhibits strong mechanical stability, retaining 80% at 25 cm2, 85% at 0.1 cm2, and 90% for semi-transparent devices of their original efficiency after 5,000 bending cycles at a curvature radius of 3 mm.
J. Mater. Chem. C, 2019, 7,9581-9590 DOI: 10.1039/C9TC02296A, Paper
Qi Wang, Miaomiao Li, Ying Sui, Zhongli Wang, Ziqi Liang, Yanhou Geng Six wide-bandgap polymers with different side chains on both benzo[1,2-b:4,5-b′]dithiophene and [2,2′-bithiophene]-4,4′-dicarboxylate units for efficient fullerene-free organic solar cells. The content of this RSS Feed (c) The Royal Society of Chemistry
by Tongle Bu,
Xueping Liu,
Jing Li,
Wenchao Huang,
Zhengli Wu,
Fuzhi Huang,
Yi-Bing Cheng,
Jie Zhong
A simple dynamic antisolvent quenching process is used for the efficient and reliable fabrications of uniform and high‐quality 10 × 10 cm2 large‐area perovskite films. The perovskite module fabricated using this technique achieves an efficiency approaching 18% and a certified efficiency of 17.4% with the aperture area of 53.64 cm2.
Perovskite solar cells represent a promising photovoltaic technology, which achieves record power conversion efficiencies over 24%. However, a problem on the commercial processing is the unavoidable efficiency loss during the scalable fabrication of perovskite solar module. The efficient and reliable fabrications of high‐quality large‐area perovskite films guarantee commercialized up‐scaling of perovskite solar cells with high efficiency. Herein, a simple dynamic antisolvent quenching (DAS) process is presented to understand large‐area uniform perovskite films to obtain an efficient perovskite solar module. This method provides a facile and universal approach to fabricate cracks‐free and uniform large‐area mixed‐cation perovskite films. A champion module device (10 × 10 cm2) with efficiency of 17.82% (another module with certified efficiency of 17.4%) is obtained using DAS process.
by Renjun Guo,
Mark V. Khenkin,
Georgios E. Arnaoutakis,
Nataliya A. Samoylova,
Jérémy Barbé,
Harrison Ka Hin Lee,
Wing Chung Tsoi,
Eugene A. Katz
The initial stages of MAPbI3 photodegradation prior to any significant change in light absorption are studied, with independent control of sample temperature and sunlight intensity (1–500 suns). Under the combined action of light and heat, a strong reduction of photoluminescence (PL) is observed. In contrast, illumination of perovskite films (with an intensity up to 500 suns) without heating induces considerable PL enhancement.
The initial stages of photo‐degradation of CH3NH3PbI3 (MAPbI3) thin films prior to any significant change in light absorption are studied in experiments with independent control of sample temperature and intensity of concentrated sunlight from 50 to 500 suns. Photo‐stability of the MAPbI3 film is revealed to be extremely sensitive to the sample temperature. Under the combined action of light and heat (either by concentrated sunlight or by external heating), a strong reduction of the film photoluminescence (PL) without changes in the perovskite light absorption can be observed during the initial stages of degradation. In contrast, illumination of perovskite films (with intensity up to 500 suns) without heating (using chopped concentrated sunlight) induces considerable PL enhancement while the optical absorption spectrum remains unchanged. With accurate temperature control, aging under concentrated sunlight results in similar instability trends as that under 1 sun.
A novel glued poly(ethylene‐co‐vinyl acetate) (EVA) interfacial layer is used to fabricate highly efficient and stable perovskite solar cells (PVSCs) with excellent waterproofness and flexibility. The EVA‐treated PVSCs exhibit superior power conversion efficiency values of 19.31% for a rigid device (0.1 cm2) and 11.73% for a solar module (25 cm2), as well as over 85% retention for a flexible device after 5000 bending cycles.
Abstract
Perovskite solar cells (PVSCs) are promising photovoltaic technologies for realizing power sources with outstanding power conversion efficiency (PCE) and low‐cost properties. However, the extraordinary photovoltaic performance can be maximized only if an extremely stabilized device structure is developed. Here, a novel glued poly(ethylene‐co‐vinyl acetate) (EVA) interfacial layer is introduced to fabricate highly efficient and stable PVSCs with excellent waterproofness and flexibility. This strategy can effectively passivate the perovskite surface, reduce defect density, and balance charge transfer, which leads to a champion PCE of 19.31% for a 0.1 cm2 device and 11.73% for a 25 cm2 solar module. More importantly, the formation of a glued EVA thin layer on the surface of perovskite can inhibit ionic migration to the Ag electrode, form favorable interfacial contact and adhesive interaction with the perovskite/[6,6]‐phenyl‐C61‐butyric acid methyl ester to sustain mechanical bending, and produce significant waterproofness from moisture invasion, thus facilitating improvement in the operational stability of the PVSCs. The EVA‐treated PVSCs exhibit superior PCE values of 15.12% for a flexible device (0.1 cm2) and 8.95% for a flexible module (25 cm2), as well as over 85% retention after 5000 bending cycles, which opens up a new strategy for the practical application of PVSCs in portable and wearable electronics.
by Cuncun Wu,
Duo Wang,
Yuqing Zhang,
Feidan Gu,
Ganghong Liu,
Ning Zhu,
Wei Luo,
Dong Han,
Xuan Guo,
Bo Qu,
Shufeng Wang,
Zuqiang Bian,
Zhijian Chen,
Lixin Xiao
A high quality FAPbI3‐based perovskite film is successfully developed via a ligand and additive synergetic process. The planar flexible solar cell based on this film shows a record power conversion efficiency of 19.38%. This device exhibits excellent ambient stability and mechanical stability.
Abstract
Compared with silicon‐based solar cells, organic–inorganic hybrid perovskite solar cells (PSCs) possess a distinct advantage, i.e., its application in the flexible field. However, the efficiency of the flexible device is still lower than that of the rigid one. First, it is found that the dense formamidinium (FA)‐based perovskite film can be obtained with the help of N‐methyl‐2‐pyrrolidone (NMP) via low pressure‐assisted method. In addition, CH3NH3Cl (MACl) as the additive can preferentially form MAPbCl3−xIx perovskite seeds to induce perovskite phase transition and crystal growth. Finally, by using FAI·PbI2·NMP+x%MACl as the precursor, i.e., ligand and additive synergetic process, a FA‐based perovskite film with a large grain size, high crystallinity, and low trap density is obtained on a flexible substrate under ambient conditions due to the synergetic effect, e.g., MACl can enhance the crystallization of the intermediate phase of FAI·PbI2·NMP. As a result, a record efficiency of 19.38% in flexible planar PSCs is achieved, and it can retain about 89% of its initial power conversion efficiency (PCE) after 230 days without encapsulation under ambient conditions. The PCE retains 92% of the initial value after 500 bending cycles with a bending radii of 10 mm. The results show a robust way to fabricate highly efficient flexible PSCs.
by Leonardo R. V. Buizza,
Timothy W. Crothers,
Zhiping Wang,
Jay B. Patel,
Rebecca L. Milot,
Henry J. Snaith,
Michael B. Johnston,
Laura M. Herz
Optoelectronic properties, including charge‐carrier dynamics and mobilities, are examined for a broad compositional range of hybrid perovskites containing 2D layered material at the boundaries of 3D perovskites grains. An optimal composition range is demonstrated that allows for good environmental stability, effective trap passivation, and efficient charge transport, making these hybrid 2D–3D materials ideal for photovoltaic and optoelectronic devices.
Abstract
Perovskite solar cells (PSCs) have improved dramatically over the past decade, increasing in efficiency and gradually overcoming hurdles of temperature‐ and humidity‐induced instability. Materials that combine high charge‐carrier lifetimes and mobilities, strong absorption, and good crystallinity of 3D perovskites with the hydrophobic properties of 2D perovskites have become particularly promising candidates for use in solar cells. In order to fully understand the optoelectronic properties of these 2D–3D hybrid systems, the hybrid perovskite BAx(FA0.83Cs0.17)1‐xPb(I0.6Br0.4)3 is investigated across the composition range 0 ≤ x ≤ 0.8. Small amounts of butylammonium (BA) are found that help to improve crystallinity and appear to passivate grain boundaries, thus reducing trap‐mediated charge‐carrier recombination and enhancing charge‐carrier mobilities. Excessive amounts of BA lead to poor crystallinity and inhomogeneous film formation, greatly reducing effective charge‐carrier mobility. For low amounts of BA, the benevolent effects of reduced recombination and enhanced mobilities lead to charge‐carrier diffusion lengths up to 7.7 µm for x = 0.167. These measurements pave the way for highly efficient, highly stable PSCs and other optoelectronic devices based on 2D–3D hybrid materials.
by Xin Song,
Nicola Gasparini,
Masrur Morshed Nahid,
Sri Harish Kumar Paleti,
Cheng Li,
Weiwei Li,
Harald Ade,
Derya Baran
Diketopyrrolopyrrole (DPP)‐based polymers have gained significant research interest in the organic electronics community. In this work, a combination of a DPP polymer derivative, PBDTT‐DPP, is used, blending with IEICO‐4F, a state‐of‐the‐art small‐molecule acceptor, yielding a champion power conversion efficiency of 9.66%, among the best performance of DPP‐based solar cells.
Abstract
The high crystallinity and ability to harvest near‐infrared photons make diketopyrrolopyrrole (DPP)‐based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP‐based OSC devices still suffer from the trade‐off between energetic loss (Eloss) and maximum external quantum efficiency (EQEmax), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP‐donor‐based solar cells due to severe charge recombination issues. In this work, efficient DPP‐based solar cells are reported using low bandgap fused ring electron acceptor, IEICO‐4F. PBDTT‐DPP:IEICO‐4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low Eloss of 0.57 eV and a high EQEmax (>70%).
by Boping Yang,
Dan Ouyang,
Zhanfeng Huang,
Xingang Ren,
Hong Zhang,
Wallace C. H. Choy
A new azeotropic promoted approach is proposed to successfully synthesize In doped CuCrO2 under low temperatures in a short time. This In doped CuCrO2 HTL has thermal stability up to 200 °C, and exhibits improved optical transmission and carrier mobility, which is beneficial for achieving high performance perovskite solar cells.
Abstract
While there are very limited studies of doped ternary metal oxide based hole transport materials, a multifunctional synthesis approach of In doped CuCrO2 nanoparticles (NPs) as efficient hole transport layers (HTLs) including simplifying the synthesis requirements is proposed, enabling doping and achievement of treatment‐free HTLs. Remarkably, compared with conventional methods for synthesizing CuCrO2 NPs, the newly proposed azeotropic promoted approach dramatically reduces the reaction time by 90% and the calcination temperature by one‐third, which not only promotes high throughput production but also reduces power consumption and cost in synthesis. Equally important, indium is successfully doped into CuCrO2, which is fundamentally difficult in low temperature processes. The In doping offers less d–d transition of Cr3+ and p‐type doping characteristics for improving HTL transmittance and conductivity, respectively. Interestingly, In doped CuCrO2 HTL with these improvements can be achieved by a simple ambient‐condition process and exhibits thermal stability up to 200 °C, which allows perovskite solar cells (PSCs) to achieve a power conversion efficiency of 20.54%. Meanwhile, the devices show good repeatability and photostability. Consequently, the work contributes to establishing a simple approach to realize pristine and doped multinary oxides based HTL for the development of practical and high performing PSCs.
by Kelly Schutt,
Pabitra K. Nayak,
Alexandra J. Ramadan,
Bernard Wenger,
Yen‐Hung Lin,
Henry J. Snaith
Perovskite solar cells with ZnO exhibit greatly improved stability when the methylammonium cation is excluded. The interfacial acid‐base reactions between methylammonium and ZnO are probed and the degradation kinetics are modulated by the acidity of the organic cation. Solar cells on ZnO films provide improved open circuit voltage, lower series resistance, and lower processing temperatures than those on SnO2.
Abstract
Perovskite solar cells have achieved the highest power conversion efficiencies on metal oxide n‐type layers, including SnO2 and TiO2. Despite ZnO having superior optoelectronic properties to these metal oxides, such as improved transmittance, higher conductivity, and closer conduction band alignment to methylammonium (MA)PbI3, ZnO is largely overlooked due to a chemical instability when in contact with metal halide perovskites, which leads to rapid decomposition of the perovskite. While surface passivation techniques have somewhat mitigated this instability, investigations as to whether all metal halide perovskites exhibit this instability with ZnO are yet to be undertaken. Experimental methods to elucidate the degradation mechanisms at ZnO–MAPbI3 interfaces are developed. By substituting MA with formamidinium (FA) and cesium (Cs), the stability of the perovskite–ZnO interface is greatly enhanced and it is found that stability compares favorably with SnO2‐based devices after high‐intensity UV irradiation and 85 °C thermal stressing. For devices comprising FA‐ and Cs‐based metal halide perovskite absorber layers on ZnO, a 21.1% scanned power conversion efficiency and 18% steady‐state power output are achieved. This work demonstrates that ZnO appears to be as feasible an n‐type charge extraction layer as SnO2, with many foreseeable advantages, provided that MA cations are avoided.
by Wei Chen,
Yingfeng Wang,
Guotao Pang,
Chang Woo Koh,
Aleksandra B. Djurišić,
Yinghui Wu,
Bao Tu,
Fang‐zhou Liu,
Rui Chen,
Han Young Woo,
Xugang Guo,
Zhubing He
A semiconducting conjugated polymer, poly(bithiophene imide), is successfully introduced to perovskite grain boundaries along with augmented grain sizes. This results in effective defect passivation and hence reduced recombination losses and increased efficiency, as well as reduced ion migration and improved stability.
Abstract
Grain boundaries in lead halide perovskite films lead to increased recombination losses and decreased device stability under illumination due to defect‐mediated ion migration. The effect of a conjugated polymer additive, poly(bithiophene imide) (PBTI), is investigated in the antisolvent treatment step in the perovskite film deposition by comprehensive characterization of perovskite film properties and the performance of inverted planar perovskite solar cells (PSCs). PBTI is found to be incorporated within grain boundaries, which results in an improvement in perovskite film crystallinity and reduced defects. The successful defect passivation by PBTI yields reduces recombination losses and consequently increases power conversion efficiency (PCE). In addition, it gives rise to improved photoluminescence stability and improved PSC stability under illumination which can be attributed to reduced ion migration. The optimal devices exhibit a PCE of 20.67% compared to 18.89% of control devices without PBTI, while they retain over 70% of the initial efficiency after 600 h under 1 sun illumination compared to 56% for the control devices.
by Hang Zhao,
Jia Xu,
Shijie Zhou,
Zhenzhen Li,
Bing Zhang,
Xin Xia,
Xiaolong Liu,
Songyuan Dai,
Jianxi Yao
Nondoped and Ca2+‐doped γ ‐CsPbI3 films are prepared at low temperature (60 °C). The theoretical simulation and experimental results testify that adding Ca2+ can lower the total cohesive energy of γ‐CsPbI3 and yield a more stable γ‐CsPbI3 film. The Ca2+‐doped γ‐CsPbI3 perovskite solar cells achieve a hysteresis‐free J–V curve and a maximum power conversion efficiency of 9.20%.
Abstract
Inorganic cubic CsPbI3 perovskite (α‐CsPbI3) has been widely explored for perovskite solar cells (PSCs) due to its thermal stability and suitable bandgap of 1.73 eV. However, α‐CsPbI3 usually requires high synthesis temperatures (>320 °C). Additionally, it usually undergoes phase transition to the nonperovskite structure phase (β‐CsPbI3), which results in poor photoelectric performance in devices. In this study, it is first found that the tortuous 3D CsPbI3 phase (γ‐CsPbI3) can be prepared and used for PSCs by solution process without any additive at low temperature (60 °C). The γ‐CsPbI3 exhibits suitable bandgap of 1.75 eV and favorable photoelectric properties. However, γ‐CsPbI3 is a metastable phase and easily transforms into β‐CsPbI3 in ambient moisture. In order to improve the stability of γ‐CsPbI3, calcium ions (Ca2+) with a relatively small radius of 100 pm are used to partially substitute lead ions (119 pm). This research proves that Ca2+ can effectively improve the stability of the γ‐CsPbI3 at room temperature. By optimizing the doping concentration of Ca2+ (CsPb1−xCaxI3, x is from 0% to 2%), the Ca2+‐doped γ‐CsPbI3 PSCs achieve a hysteresis‐free J–V curve and a maximum power conversion efficiency (PCE) of 9.20%.
Electrohydrodynamic (EHD) printing with the unique advantages of high‐resolution patterning and large scalability is introduced to fabricate full‐color perovskite patterns. Perovskite inks via simple precursor mixing are prepared to in situ crystallize tunable‐ and bright‐photoluminescence perovskite arrays without adding antisolvent. Through optimizing the EHD printing process, a high‐resolution dot matrix of 5 µm is achieved.
Abstract
Hybrid perovskites show enormous potential for display due to their tunable emission, high color purity, strong photoluminescence and electroluminescence. For display applications, full‐color and high‐resolution patterning is compulsory, however, current perovskite processing such as spin‐coating fails to meet these requirements. Here, electrohydrodynamic (EHD) printing, with the unique advantages of high‐resolution patterning and large scalability, is introduced to fabricate full‐color perovskite patterns. Perovskite inks via simple precursor mixing are prepared to in situ crystallize tunable‐ and bright‐photoluminescence perovskite arrays without adding antisolvent. Through optimizing the EHD printing process, a high‐resolution dot matrix of 5 µm is achieved. The as‐printed patterns and pictures show full color and high controllability in micrometer dimension, indicating that the EHD printing is a competitive technique for future halide perovskite‐based high‐quality display.
A novel glued poly(ethylene‐co‐vinyl acetate) (EVA) interfacial layer is used to fabricate highly efficient and stable perovskite solar cells (PVSCs) with excellent waterproofness and flexibility. The EVA‐treated PVSCs exhibit superior power conversion efficiency values of 19.31% for a rigid device (0.1 cm2) and 11.73% for a solar module (25 cm2), as well as over 85% retention for a flexible device after 5000 bending cycles.
Abstract
Perovskite solar cells (PVSCs) are promising photovoltaic technologies for realizing power sources with outstanding power conversion efficiency (PCE) and low‐cost properties. However, the extraordinary photovoltaic performance can be maximized only if an extremely stabilized device structure is developed. Here, a novel glued poly(ethylene‐co‐vinyl acetate) (EVA) interfacial layer is introduced to fabricate highly efficient and stable PVSCs with excellent waterproofness and flexibility. This strategy can effectively passivate the perovskite surface, reduce defect density, and balance charge transfer, which leads to a champion PCE of 19.31% for a 0.1 cm2 device and 11.73% for a 25 cm2 solar module. More importantly, the formation of a glued EVA thin layer on the surface of perovskite can inhibit ionic migration to the Ag electrode, form favorable interfacial contact and adhesive interaction with the perovskite/[6,6]‐phenyl‐C61‐butyric acid methyl ester to sustain mechanical bending, and produce significant waterproofness from moisture invasion, thus facilitating improvement in the operational stability of the PVSCs. The EVA‐treated PVSCs exhibit superior PCE values of 15.12% for a flexible device (0.1 cm2) and 8.95% for a flexible module (25 cm2), as well as over 85% retention after 5000 bending cycles, which opens up a new strategy for the practical application of PVSCs in portable and wearable electronics.
by Bo Chen,
Jingfeng Song,
Xuezeng Dai,
Ye Liu,
Peter N. Rudd,
Xia Hong,
Jinsong Huang
The impact of light on the stability of perovskite solar cells (PSCs) is comprehensively investigated. Elevated device temperature and excess charge carriers are the driving forces for defect formation and PSC device degradation under illumination, not the photovoltage or strain. Cooling the device and operating at maximum power point can improve PSC stability.
Abstract
With power conversion efficiencies now reaching 24.2%, the major factor limiting efficient electricity generation using perovskite solar cells (PSCs) is their long‐term stability. In particular, PSCs have demonstrated rapid degradation under illumination, the driving mechanism of which is yet to be understood. It is shown that elevated device temperature coupled with excess charge carriers due to constant illumination is the dominant force in the rapid degradation of encapsulated perovskite solar cells under illumination. Cooling the device to 20 °C and operating at the maximum power point improves the stability of CH3NH3PbI3 solar cells over 100× compared to operation under open circuit conditions at 60 °C. Light‐induced strain originating from photothermal‐induced expansion is also observed in CH3NH3PbI3, which excludes other light‐induced‐strain mechanisms. However, strain and electric field do not appear to play any role in the initial rapid degradation of CH3NH3PbI3 solar cells under illumination. It is revealed that the formation of additional recombination centers in PSCs facilitated by elevated temperature and excess charge carriers ultimately results in rapid light‐induced degradation. Guidance on the best methods for measuring the stability of PSCs is also given.
