Energy Environ. Sci., 2019, 12,3063-3073 DOI: 10.1039/C9EE01773A, Paper
Nakita K. Noel, Severin N. Habisreutinger, Alba Pellaroque, Federico Pulvirenti, Bernard Wenger, Fengyu Zhang, Yen-Hung Lin, Obadiah G. Reid, Johannes Leisen, Yadong Zhang, Stephen Barlow, Seth R. Marder, Antoine Kahn, Henry J. Snaith, Craig B. Arnold, Barry P. Rand We demonstrate a method for controlled p-doping of the halide perovskite surface using molecular dopants, resulting in reduced non-radiative recombination losses and improved device performance. The content of this RSS Feed (c) The Royal Society of Chemistry
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.
Author(s): Xiaolong Yang, Jun Xi, Yuanhui Sun, Yindi Zhang, Guijiang Zhou, Wai-Yeung Wong
Abstract
Low-cost solution-processable inverted perovskite solar cells (PSCs) demonstrate great potential toward future photovoltaic market. Unfortunately, general hole transport materials (HTMs) within inverted structure make the performance and stability far uncompetitive compared to the normal structure. Interrogating the fundamentals of these materials, moderate charge carrier mobility and susceptible environmental stability of the undoped molecules are the main causes. Herein, a twisted molecule XY1 is developed as a potential robust dopant-free HTM for inverted PSCs. Compared with traditional poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), XY1 exhibits much higher hole transport ability and peculiar ultraviolet absorption. Hysteresis-free inverted PSCs based on XY1 exhibits the power conversion efficiency (PCE) of 18.78%, which is among the highest values for inverted PSCs based on dopant-free HTMs. After light soaking for 200 h, the original PCE of XY1-based device is still maintained at the 95% level, indicating the substantially improved operational stability. Besides, large-area (1.00 cm2) inverted PSC based on XY1 shows a competitive PCE of 17.82%.
Graphical abstract
The twisted organic small-molecule hole transport material XY1 exhibits advantages such as good film morphology, strong absorption in the UV range but high transmittance in the visible and near-infrared range, high hole mobility, and perfect energy level alignment with the perovskite layer. Consequently, both small- and large-area inverted perovskite solar cells based on the dopant-free XY1 show state-of-the-art photovoltaic performance.
For commercialization of perovskite solar cells (PSCs), the device stability issues attributed to degradation of perovskite material, photo and thermal instability, and photocurrent density-voltage (J-V) hysteresis behavior should be solved. Furthermore, most of presented high efficiency PSCs utilize an antisolvent-strategy to assist perovskite crystal growth with large grain-size and excellent coverage. To solve such issues, we developed fully-ambient-air and antisolvent-free processes for the fabrication of PSCs with perovskite-based composites (i.e., MAPbI3-xClx-Cu:NiO, MAPbI3-xClx-Cu:NiO-carbon-graphite and MAPbI3-xClx-Al2O3). Such perovskite composites based cells with interface engineering yielded high power-conversion-efficiency (PCE) of 18.6% and fill factor (FF) of 78.3% with excellent reproducibility. More importantly, the target cells showed hysteresis-free behavior and dramatic enhancement in air-, photo- and thermal-stability. Compared to the pristine cells, the target device showed remarkable long-term stability with retaining almost 100% of the initial values of Voc and Jsc, and ~94% of FF and PCE over 280 days.
Graphical abstract
Schematic illustration and conceptual mechanism of stable perovskite solar cells by perovskite-based-composites and interface engineering.
Author(s): Shengbo Ma, Hengxing Xu, Miaosheng Wang, Jiajun Qin, Ting Wu, Ping Chen, Bin Hu
Abstract
Polarization effects on optoelectronic behaviors in perovskite-based devices are difficult to address due to quick electronic polarization relaxation and ionic polarization from mobile ions. Here we show the effects of polarized excited states on photoluminescence and photocurrent in MAPbBr3 thin-film devices. We found optically polarized transition dipoles, oriented paralleled and perpendicular to device built-in field, give rise to significantly different photoluminescence and photocurrent outcomes. It provides a new understanding that controlling domain geometry can further enhance the light-emitting and photovoltaic performance of perovskite-based applications. The observation proves that the anisotropy of photoexcited transition dipoles is existed in the electronic states of MAPbBr3. Particularly, this indicates that photo-induced electronic polarization can be shown as photoinduced dielectric polarization at the dipolar polarization regime, which impacts device performance. We also observed that increasing photoexcitation intensity leads to a decreases on both field-induced photoluminescence quenching and field-induced photocurrent enhancing, which implies a cooperative interaction between transition dipoles of increased density that favors light emission but infavors charge dissociation. This provides a critical understanding on why organic-inorganic hybrid perovskites can function as efficient photovoltaic and light-emitting materials at low and high excitation intensities, respectively. Our estimation shows that, by manipulating the ratio of dipole orientation, the efficiencies of perovskite-based LEDs and solar cells could be improved by 50% and 18%, respectively. Clearly, the polarization effect presents a new insight on further controlling photovoltaic and light-emitting actions by manipulating the polarization of excited states in perovskite optoelectronics.
Operational stability remains the foremost concern delaying the commercialization of perovskite solar cells (PSCs). Ions diffusion from iodine-rich perovskite layer to metal electrode is one main reason for the irreversible devices degradation. Here we introduce chemically crosslinked TMTA (trimethylolpropane triacrylate) at both bulk perovskite layer and perovskite/PCBM interface to suppress the ions diffusion toward electrode. The TMTA in perovskite layer suppresses ions migration along grain boundaries and TMTA at perovskite/PCBM interface blocks ions diffusion toward electrode, owing to its continuous network structure and chemically inert nature. Diffusion experiment, permeation experiment and resistive random-access memory (RRAM) investigation confirm the effectively blocked ions diffusion in PSCs with TMTA whether under heat, light or electric field conditions. The resulting PSCs exhibit 7-fold improvement in operational stability at elevated temperature of 60 °C, retaining ~80% of initial efficiency after maximum power point tracking for 1000 h under continuous illumination. The PSCs with TMTA also exhibit good thermal stability and retain over 90% of the initial efficiency after aging at 60 °C for 1000 h.
Graphical abstract
Operationally stable perovskite solar cells (PSCs) are fabricated through introducing chemically crosslinked TMTA (trimethylolpropane triacrylate) at both bulk perovskite layer and perovskite/PCBM interface. TMTA in perovskite layer suppresses ions migration along grain boundaries and TMTA at perovskite/PCBM interface blocks ions diffusion toward electrode. The ions diffusion in PSCs is effectively suppressed whether under heat, light or electric field conditions. The resulting PSCs retain ~80% of initial efficiency after MPP tracking at 60 °C for 1000 h.
by Jishan Shi,
Yerun Gao,
Xiang Gao,
Yun Zhang,
Junjie Zhang,
Xin Jing,
Ming Shao
A remarkable high efficiency of 17.34% is achieved for low‐dimensional Ruddlesden–Popper perovskite (RPP) solar cells (n ≤ 5) by using a fluorinated phenylethalammonium (4‐fluoro‐phenethylammonium (4FPEA)) organic cation. These fluorinated devices also show the better humidity and thermal stability as compared to nonfluorinated phenylethlammonium (PEA) devices. These findings provide a feasible approach for simultaneously improving the efficiency and stability of low‐dimensional RPP solar cells.
Abstract
Low‐dimensional Ruddlesden–Popper perovskites (RPPs) exhibit excellent stability in comparison with 3D perovskites; however, the relatively low power conversion efficiency (PCE) limits their future application. In this work, a new fluorine‐substituted phenylethlammonium (PEA) cation is developed as a spacer to fabricate quasi‐2D (4FPEA)2(MA)4Pb5I16 (n = 5) perovskite solar cells. The champion device exhibits a remarkable PCE of 17.3% with a Jsc of 19.00 mA cm−2, a Voc of 1.16 V, and a fill factor (FF) of 79%, which are among the best results for low‐dimensional RPP solar cells (n ≤ 5). The enhanced device performance can be attributed as follows: first, the strong dipole field induced by the 4‐fluoro‐phenethylammonium (4FPEA) organic spacer facilitates charge dissociation. Second, fluorinated RPP crystals preferentially grow along the vertical direction, and form a phase distribution with the increasing n number from bottom to the top surface, resulting in efficient charge transport. Third, 4FPEA‐based RPP films exhibit higher film crystallinity, enlarged grain size, and reduced trap‐state density. Lastly, the unsealed fluorinated RPP devices demonstrate superior humidity and thermal stability. Therefore, the fluorination of the long‐chain organic cations provides a feasible approach for simultaneously improving the efficiency and stability of low‐dimensional RPP solar cells.
by Yiming Bai,
Kun Lang,
Chunyan Zhao,
Qiang Guo,
Rui Zeng,
Jun Wang,
Tasawar Hayat,
Ahmed Alsaedi,
Zhanao'ao Tan
This review aims at presenting a comprehensive overview of the latest progress on perovskite solar cells (PSCs), especially the strategies toward enhancing their near‐infrared light harvesting. An in‐depth understanding of the working mechanism of tandem solar cells (TSCs) and integrated perovskite/organic solar cells (IPOSCs) is presented, and the recent developments of perovskite/Si, perovskite/Cu(In1–x, Gax)Se2 TSCs, and IPOSCs are further highlighted.
The emerging perovskite materials present great opportunities for cost‐saving and efficient photovoltaic devices. However, perovskite solar cells (PSCs) suffer from the limitation of short optical absorption edge, resulting in most of the near‐infrared (NIR) light being wasted. Recently, strategies toward broadening the NIR spectra response and further improve the power conversion efficiency of PSCs have attracted extensive attention. In this review, the unique features of perovskite materials are first introduced; subsequently, the current developments of organic–inorganic hybrid PSCs and all‐inorganic PSCs are highlighted. Then, a detailed summary of the strategies toward enhancing the NIR light harvesting of PSCs, namely, perovskite/Si and perovskite/Cu(In1–x, Gax)Se2 tandem solar cells (TSCs) and the integrated perovskite/organic solar cells (IPOSCs), is presented. After an in‐depth understanding of the working mechanism of TSCs and IPOSCs, a comprehensive overview about their recent developments, key detrimental factors restricting their further performance enhancement, and feasible countermeasures to conquer these scientific and technological problems are given. In the end, the perspectives on the related materials and devices are addressed.
by Chunyan Lu,
Ziyang Hu,
Yanyan Wang,
Can Gao,
Cheng Yang,
Jing Zhang,
Yuejin Zhu
The location and distribution of fullerenes in the perovskite:fullerene hybrid phase are confirmedly visualized by the conductive atomic force microscopy and Kelvin probe force microscopy measurements. Macroscopic current hysteresis originating from the influxes of all nanoscopic grain boundary current is avoided in perovskite solar cells based on the hybrid perovskite:fullerene phases.
In perovskite solar cells (PSCs), hybrid perovskite:fullerene phases are proposed to suppress macroscopic current hysteresis behavior by alleviating ion migration. However, the understanding of how fullerenes exactly alleviate the current hysteresis and what is the influence of fullerenes in such hybrid phases are still unclear from a microscopic viewpoint. Herein, the intentional incorporation of fullerene into perovskite is used to examine how fullerene exactly reduces the macroscopic current hysteresis. The location and distribution of fullerenes in the hybrid phase are confirmedly visualized using conductive atomic force microscopy and Kelvin probe force microscopy measurements. Fullerenes located at grain boundaries function as a source of beneficial effect on choking the channels of ion migration and also as the electron traps that compromise the photocarrier extraction. Macroscopic current hysteresis originating from the influxes of all nanoscopic grain boundary current signals is avoided in PSCs based on the hybrid perovskite:fullerene phases. These results not only provide a strong correlation between nanoscopic and macroscopic current hysteresis behaviors but also clearly clarify how fullerenes play a role in reducing the current hysteresis in hybrid phases and thus prototype devices.
by Peng Zhao,
Liping Feng,
Zhenhua Lin,
Jiaping Wang,
Jie Su,
Zhaosheng Hu,
Jincheng Zhang,
Xiaoping Ouyang,
Jingjing Chang,
Yue Hao
A comprehensive theoretical analysis of two‐terminal and four‐terminal perovskite/copper indium gallium selenide (CIGS) tandem solar cells is investigated from optical and electrical aspects. According to different optical absorptions, the current matching points of different halide components are obtained. Under the condition of current matching, an optimal performance up to 31.13% can be obtained by using two‐terminal CH3NH3PbI2Br/CIGS tandem structure.
Perovskite/copper indium gallium selenide (CIGS) tandem solar cells represent an attractive configuration to obtain ultrahigh efficiency. A detailed theoretical analysis is crucial for further improving the performance of tandem solar cells. Herein, four‐terminal and two‐terminal perovskite/CIGS tandem solar cells are intensively researched. For four‐terminal perovskite/CIGS tandem solar cell, the optimal thicknesses of CH3NH3PbI3 and CIGS are 0.5 and 3 μm, respectively, according to the simulation result. Reducing the thickness of TiO2 and Spiro‐OMeTAD can minimize the short‐wavelength parasitic absorption and long‐wavelength parasitic absorption, respectively. Meanwhile, using antireflection coating, such as 100 nm MgF2, is beneficial to increase the photon absorption. For two‐terminal perovskite/CIGS tandem solar cells, the thicknesses of perovskite and CIGS are tuned to meet the current matching. To further improve the efficiency of two‐terminal tandem cells, FTO thickness is reduced to minimize reflection, and the optimal doping concentration of CIGS (1 × 1018 cm−3) is used. In addition, results show that the quality of perovskite films should be improved by enlarging the grain size to decrease the trap states at grain boundary. Finally, the optimal efficiency of two‐terminal CH3NH3PbI2Br/CIGS tandem solar cells reaches 31.13%.
by Zonglong Song,
Wenbo Bi,
Xinmeng Zhuang,
Yanjie Wu,
Boxue Zhang,
Xinfu Chen,
Cong Chen,
Qilin Dai,
Hongwei Song
Efficient Zn‐SnOx electron transport layers (ETLs) by the low‐temperature (100 °C) electron beam (E‐beam) method are prepared. Doping Zn2+ in SnO2 improves conductivity, suppresses charge recombination, and optimizes the energy level structure of SnO2, leading to an improved power conversion efficiency from 18.95% to 20.16%. The low‐temperature preparation of ETLs and the excellent performance of devices present great commercial potential for future applications.
Perovskite solar cells (PSCs) attract tremendous interest due to their feasibility, high power conversion efficiency (PCE), light weight, and flexible architecture. However, some challenges are still present for cheap mass fabrication in commercial applications. Herein, efficient Zn‐SnOx electron transport layers (ETLs) are used by the low‐temperature (100 °C) electron beam (E‐beam) method. Doping Zn2+ in SnO2 improves conductivity, suppresses charge recombination, and optimizes the energy level structure of SnO2, leading to an improved PCE from 18.95% to 20.16%. More importantly, the PCE of the modified device is more than 80% of its initial values for 800 h in ambient air with a relative humidity of ≈40%. The flexible device exhibits a PCE of 15.25% and remains at an initial PCE of 83% after 100 bending cycles. The efficient and flexible PSCs are potentially used as wearable energy power sources. The low‐temperature preparation of ETL and the excellent performance of devices present great commercial potential for future applications.
Herein, Pb‐site doping in organic–inorganic hybrid perovskite (OIH‐LHP) and inorganic CsPbX3‐based materials is discussed, elucidating the functions of doping on lead halide perovskite (LHP) crystallization, optoelectronic property, and stability. Perspectives for further investigation are also presented.
Although great success has been achieved in perovskite solar cells (PSCs), it still suffers from several drawbacks in terms of stability and higher efficiency. Doping as an effective method to modify the optical and electronic properties of the materials is extensively studied in lead halide perovskites (LHPs). Herein, Pb‐site doping in organic–inorganic hybrid perovskites (OIH‐LHPs) and inorganic CsPbX3‐based materials is discussed. Doping has three functions toward PSCs: participating in the crystalline process, modifying the energy states in LHPs, and contributing to the stability of PSCs. Issues about further improvements are raised, and perspectives for further investigation are presented.
by Patrik S?c?ajev†, Ramu¯nas Aleksieju¯nas*†, Paulius Baronas†, Dz?iugas Litvinas†, Marek Kolenda†, Chuanjiang Qin‡§, Takashi Fujihara?, Toshinori Matsushima?‡§, Chihaya Adachi?‡§, and Saulius Jurs?e?nas†
by Jianfeng Lu†‡, Andrew D. Scully§, Jingsong Sun‡?, Boer Tan†‡, Anthony S. R. Chesman§?, Sonia Ruiz Raga†‡, Liangcong Jiang‡?, Xiongfeng Lin†‡, Narendra Pai#, Wenchao Huang?, Yi-Bing Cheng??, Udo Bach*†‡§?, and Alexandr N. Simonov*#?
by Yucheng Zhang,
Yusen Zhao,
Dong Wu,
Jingjing Xue,
Yu Qiu,
Michael Liao,
Qibing Pei,
Mark S. Goorsky,
Ximin He
A facile low‐energy‐cost one‐pot scalable preparation strategy is developed to achieve homogeneously dispersed organic–inorganic perovskites nanoparticles in a freestanding gel with superior stability and high color purity even in water. The modular material design allows for a broad range of mechanical properties tunable from high elasticity stretchable gel in LEDs to rigid arbitrary 2D/3D structures printed by fast 3D‐printing technology.
Abstract
Metal‐halide perovskites have become appealing materials for optoelectronic devices. While the fast advancing stretchable/wearable devices require stability, flexibility and scalability, current perovskites suffer from ambient‐environmental instability and incompatible mechanical properties. Recently perovskite−polymer composites have shown improved in‐air stability with the protection of polymers. However, their stability remains unsatisfactory in water or high‐humidity environment. These methods also suffer from limited processability with low yield (2D film or beads) and high fabrication cost (high temperature, air/moisture‐free conditions), thereby limiting their device integration and broader applications. Herein, by combining facile photo‐polymerization with room‐temperature in‐situ perovskite reprecipitation at low energy cost, a one‐step scalable method is developed to produce freestanding highly‐stable luminescent organogels, within which CH3NH3PbBr3 nanoparticles are homogeneously distributed. The perovskite‐organogels present a record‐high stability at different pH and temperatures, maintaining their high quantum yields for > 110 days immersing in water. This paradigm is universally applicable to broad choices of polymers, hence casting these emerging luminescent materials to a wide range of mechanical properties tunable from rigid to elastic. With intrinsically ultra‐stretchable photoluminescent organogels, flexible phosphorous layers were demonstrated with > 950% elongation. Rigid perovskite gels, on the other hand, permitted the deployment of 3D‐printing technology to fabricate arbitrary 2D/3D luminescent architectures.
Author(s): Zhenye Li, Wenkai Zhong, Lei Ying, Feng Liu, Ning Li, Fei Huang, Yong Cao
Abstract
Organic solar cells with excellent device performance and stability are essential for both academic and industrial purposes. The molecular weight (Mn) of donor polymers plays a critical role in determining the photovoltaic properties of all-polymer solar cells (all-PSCs). Despite Mn of donor polymers has pronounced effects on microstructure morphology, photovoltaic performance and stability of all-PSCs are rarely analyzed and understood in high-performance devices. In this study, we systematically investigate the influence of Mn of donor polymers on the device performance metrics and device stability of all-PSCs comprising of a wide-bandgap polymer donor PTzBI-Si and a polymer acceptor N2200. All-PSCs based on high Mn of PTzBI-Si exhibit an excellent PCE of 11.5% with improved stability, which is clearly superior to that of all-PSCs based on low Mn of PTzBI-Si. The photovoltaic performance difference caused by Mn of PTzBI-Si is systematically characterized and analysed to establish the morphology-property-performance correlation. The findings demonstrated in our model system suggest that tuning the Mn of donor polymer could be a facile and promising strategy to simultaneously enhance the efficiency and stability of all-PSCs.
