J. Mater. Chem. A, 2020, 8,2644-2653 DOI: 10.1039/C9TA11344D, Paper
Jinbo Chen, Hua Dong, Lin Zhang, Jingrui Li, Fuhao Jia, Bo Jiao, Jie Xu, Xun Hou, Jian Liu, Zhaoxin Wu The energy level alignment and carrier mobility of the charge transport layer are of crucial importance for electron extraction and transport in planar heterojunction perovskite solar cells (PSCs). The content of this RSS Feed (c) The Royal Society of Chemistry
J. Mater. Chem. A, 2020, 8,1131-1137 DOI: 10.1039/C9TA12605H, Communication
Tsung-Wei Chen, Kuan-Lin Peng, You-Wei Lin, Yi-Jia Su, Ko-Jui Ma, Ling Hong, Chia-Chih Chang, Jianhui Hou, Chain-Shu Hsu A systematic approach involving conjugation extension and end group chlorination is capable of enhancing both JSC and PCE. Overall, the PM6:DTTC-4Cl-based device delivers a remarkable PCE of 15.42% with a VOC of 0.92 V, a JSC of 22.64 mA cm−2 and an FF of 74.04%. The content of this RSS Feed (c) The Royal Society of Chemistry
Author(s): Jingjing Jiang, Rajiv Giridharagopal, Erin Jedlicka, Kaiwen Sun, Shaotang Yu, Sanping Wu, Yuancai Gong, Weibo Yan, David S. Ginger, Martin A. Green, Xiaojing Hao, Wei Huang, Hao Xin
Abstract
Theoretical calculation suggests Cu-rich chalcopyrite absorbers contain less defects and have potential to achieve better performance than Cu-poor absorbers. However, this has not been demonstrated due to the detrimental Cu2-xSe impurity remaining in the absorber. Here, we report highly efficient Cu-rich chalcopyrite solar cells by selenizing dimethylformamide molecular precursor solution processed precursor films under high Ar pressure. Characterizations using XRD, Raman, SEM, TEM, c-AFM, PL, and glow discharge optical emission spectroscopy (GDOES) show high pressure selenization enables high quality Cu-rich chalcopyrite absorber materials with stoichiometric composition, smooth surface, high conductivity, and Cu2-xSe free grain boundaries, leading to efficient CuIn(S,Se)2 and Cu(In,Ga)(S,Se)2 devices with power conversion efficiency of 14.5% and 15.2%, both are the best performing chalcopyrite solar cells from non-hydrazine solutions. Our results demonstrate high Ar pressure selenization is a new strategy to fabricate high quality Cu-rich absorber which has great potential to further improve chalcopyrite solar cell efficiency.
Graphical abstract
CIS solar cell with an efficiency of 14.5% is achieved from Cu-rich ([Cu]/[In] = 1.05) absorber fabricated from DMF molecular solution by high pressure selenization, which is 9.96% for Cu-poor ([Cu]/[In] = 0.85) device. The Cu-rich absorber has stoichiometric composition, smooth surface, high conductivity, and Cu2-xSe free grain boundaries. This is the first time highly efficient chalcopyrite solar cell is demonstrated from Cu-rich absorbers.
J. Mater. Chem. A, 2020, 8,2039-2046 DOI: 10.1039/C9TA12597C, Paper
Qingquan He, Michael Worku, Liangjin Xu, Chenkun Zhou, Sandrine Lteif, Joseph B. Schlenoff, Biwu Ma A new class of materials, phosphonium halide salts, are used as surface passivation agents for efficient and stable PSCs. The content of this RSS Feed (c) The Royal Society of Chemistry
Flexible solar cells have launched potential applications in diverse areas, such as civil engineering, consumer electronics, electric automobile and aerospace use. In recent years, perovskite solar cells have been such successful with a rocketing power conversion efficiency (PCE) from 3.8% to 25.2% within the last decade. Owing to its material flexibility, together with low‐cost and facile fabrication processes, perovskites have certainly been considered as a promising candidate for the next generation of flexible solar cells. So far, the PCE of single‐junction flexible perovskite solar cells (FPSCs) have reached 19.51%, which retains researchers’ great enthusiasm for further development and applications of FPSCs. Here, we present a brief review of recent advances of device structural components of FPSCs, including perovskite absorber layers, flexible substrates, transparent bottom electrodes, and charge carrier transport layers. Especially, we put a focus on development of low‐temperature fabrication processes of above compositional layer structures. Finally, noticeable achievements and annual milestones are discussed and summarized, and suggestions for further improvement of FPSCs and their ways towards commercialization are presented.
This article is protected by copyright. All rights reserved.
by María Privado,
Prateek Malhotra,
Pilar de la Cruz,
Rahul Signal,
Jesús Cerdá,
Juan Aragó,
Enrique Ortí,
Ganesh D. Sharma,
Fernando Langa
A new and simple near‐IR absorbing non‐fullerene acceptor (NFA), MPU4, has been easily synthesized in three steps from an accessible selenophene‐diketopyrrolopyrrole and rhodanine. The high planarity of the molecule and the extended conjugation determine that the new NFA presented a high optical absorption coefficient and a narrow bandgap. In thin film, MPU4 shows a broad absorption in the visible and near‐IR regions from 550 nm to 930 nm. When blended with a phenothiazine‐based small‐molecule donor, SM1, the resulting additive‐free binary solar cell exhibited an efficiency of 8.96% with a high open‐circuit voltage (Voc) of 0.99 V and a short‐circuit current (Jsc) of 14.91 mA cm–2 with a remarkably low energy loss (Eloss) of 0.42 eV. This efficiency is significantly higher (24%) than that achieved with an analogous device with a thiophene‐containing NFA (MPU1, 7.22%) instead of the selenophene‐based MPU4. Importantly, ternary solar cells prepared with SM1 as the donor and MPU4 and PC71BM as acceptors afforded, after solvent vapor annealing, an efficiency of 10.04% with Voc of 0.92 V, Jsc of 16.32 mA cm–2, a fill factor (FF) of 0.67, and an Eloss of 0.49 eV. These results demonstrate the advantages of using selenophene instead of thiophene in small‐molecule organic solar cells.
This article is protected by copyright. All rights reserved.
by Lei Ran,
Jungang Hou,
Shuyan Cao,
Zhuwei Li,
Yanting Zhang,
Yunzhen Wu,
Bo Zhang,
Panlong Zhai,
Licheng Sun
Solar energy conversion is one of the most versatile approaches for of sustainable energy demands. The fundamental limitations for the photocatalysis still remain by light absorption, charge separation and photocatalytic performance of the catalysts. For the past decades, defect engineering is proven as a promising solution of converting solar energy to chemical energy. In this regard, the recent progress of defect engineering toward solar energy conversion is summarized. Take the defects classification as the beginning, the definition of various defects, the synthesized strategies and characterization techniques of the controllable material defects are presented. The role of defect engineering on solar energy conversion is developed, extending light absorption, promoting charge separation, and facilitating stable photocatalytic reaction. Typically, the achievement of the defective photocatalysts has been discussed toward versatile applications such as solar water splitting, CO2 reduction, nitrogen fixation, molecular activation, pollutants degradation and solar cells. Finally, this review with regard to defect engineering ends with the future opportunities and challenges on the exciting and emerging area for solar energy conversion.
This article is protected by copyright. All rights reserved.
by Thaer Kassar,
Marvin Berlinghof,
Nusret Sena Güldal,
Tilo Schmutzler,
Federico Zontone,
Marco Brandl,
Ezzeldin Metwalli,
Johannes Will,
Ning Li,
Tayebeh Ameri,
Christoph J. Brabec,
Tobias Unruh
Fullerene intercalation between the side chains of conjugated polymers has a detrimental impact on both charge separation and charge transport processes in bulk heterojunction (BHJ) organic photovoltaic cells (OPVs). In situ grazing incidence X‐ray scattering experiments allow to characterize the structure formation, drying kinetics and intercalation in blends of phenyl‐c61‐butyric acid methyl ester (PC60BM) and poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) named (pBTTT‐C14) from their 1,2‐orthodichlorobenzene (oDCB) solutions with different volume fractions of dodecanoic acid methyl ester (Me12) as a solvent additive. The structure formation process during evaporation of the solvent:additive mixture can be described by five periods, which are correlated to a multi‐step contraction of the lamellar stacking of the bimolecular crystals. The onset of crystallization is delayed by increasing the additive volume fraction in the coating solution leading to a promoted crystallinity. A conclusive picture of fullerene intercalation and additive‐tuned structural evolution during the drying of thin films of the polymer:fullerene BHJ blends will be presented.
This article is protected by copyright. All rights reserved.
by Long Hu†?, Yutao Wang?, Sunil B. Shivarudraiah†, Jianyu Yuan§, Xinwei Guan?, Xun Geng?, Adnan Younis?, Yicong Hu‡, Shujuan Huang?, Tom Wu*?, and Jonathan E. Halpert*†
J. Mater. Chem. A, 2020, 8,3145-3153 DOI: 10.1039/C9TA10763K, Paper
Bing Liu, Rongli Cui, Huan Huang, Xihong Guo, Jinquan Dong, Huanli Yao, Ying Li, Dangui Zhao, Jiahao Wang, Jing Zhang, Yu Chen, Baoyun Sun In this study, the stability mechanism of the optimized methyl ammonium lead triiodide (CH3NH3PbI3, MAPbI3)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) perovskite active layer upon exposure to moisture, light, and heating was investigated. The content of this RSS Feed (c) The Royal Society of Chemistry
Gadolinium fluoride (GdF3) and aminobutanol are introduced for Ostwald ripening in the crystal growth of perovskite to overcome the double dilemma of internal defects and external humidity. The GdF3‐ and aminobutanol‐treated perovskite solar cell achieves a power conversion efficiency of 21.21% with good stability and small hysteresis, while the pristine device only shows an efficiency of 18.10%.
Abstract
As one kind of promising next‐generation photovoltaic devices, perovskite solar cells (PVSCs) have experienced unprecedented rapid growth in device performance over the past few years. However, the practical applications of PVSCs require much improved device long‐term stability and performance, and internal defects and external humidity sensitivity are two key limitation need to be overcome. Here, gadolinium fluoride (GdF3) is added into perovskite precursor as a redox shuttle and growth‐assist; meanwhile, aminobutanol vapor is used for Ostwald ripening in the formation of the perovskite layer. Consequently, a high‐quality perovskite film with large grain size and few grain boundaries is obtained, resulting in the reduction of trap state density and carrier recombination. As a result, a power conversion efficiency of 21.21% is achieved with superior stability and negligible hysteresis.
by Qing Liao,
Qian Kang,
Yi Yang,
Cunbin An,
Bowei Xu,
Jianhui Hou
Novel cathode interlayers (CILs) are developed by tailoring an organic electron acceptor, viz. ITIC. A high efficiency of 16.6% is achieved in an organic solar cell with S‐3 as the CIL. It is demonstrated that the difference of electrostatic surface potential between the CIL molecule and the polymer donor can promote exciton dissociation, contributing to additional charge generation.
Abstract
With the rapid advance of organic photovoltaic materials, the energy level structure, active layer morphology, and fabrication procedure of organic solar cells (OSCs) are changed significantly. Thus, the photoelectronic properties of many traditional electrode interlayers have become unsuitable for modifying new active layers; this limits the further enhancement in OSC efficiencies. Herein, a new design strategy of tailoring the end‐capping unit, ITIC, to develop a cathode interlayer (CIL) material for achieving high power conversion efficiency (PCE) in OSCs is demonstrated. The excellent electron accepting capacity, suitable energy level, and good film‐forming ability endow the S‐3 molecule with an outstanding electron extraction property. A device with S‐3 shows a PCE of 16.6%, which is among the top values in the field of OSCs. More importantly, it is demonstrated that the electrostatic potential difference between the CIL molecule and the polymer donor plays a crucial role in promoting exciton dissociation at the CIL/active layer interface, contributing to additional charge generation; this is crucial for enhancement of the current density. The results of this work not only develop a new design strategy for high‐performance CIL, but also demonstrate a reliable approach of density functional theory (DFT) calculation to predict the effect of the CIL chemical structure on exciton dissociation in OSCs.
by Zhongze Liu,
Fengren Cao,
Meng Wang,
Min Wang,
Liang Li
All held together: A simple post‐treatment procedure uses 2‐aminoterephthalic acid as a cross‐linking agent to modify the exposed grain boundary of perovskite film, which is directly observed with conductive atomic force microscopy (C‐AFM). Under the optimized cross‐linking agent concentration, a solar cell achieves a power conversion efficiency (PCE) of 21.09 % and improved stability.
Abstract
Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post‐treatment procedure involves applying 2‐aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post‐treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2‐aminoterephthalic acid acted as a cross‐linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.
by Lu Qiao,
Wei-Hai Fang,
Run Long,
Oleg V. Prezhdo
Defects, such as halide interstitials, form inevitably during synthesis, act as charge recombination centers, induce degradation of halide perovskites, and create major obstacles to multiple applications of these widely popular materials. Recent experiments uncovered that alkali metal dopants greatly improve perovskite performance. Using state‐of‐the‐art ab initio nonadiabatic molecular dynamics we demonstrate that alkalis bring multiple favorable effects and rationalize the atomistic mechanisms. The formation energy of halide interstitials increases by up to a factor of four in the presence of alkali dopants, and therefore, defect concentration decreases. When defects are present, alkali metals strongly bind to them. Halide interstitials introduce midgap states that rapidly trap charge carriers. Alkalis eliminate the trap states, helping to maintain high current density. In addition to charge trapping, the interstitials accelerate charge recombination. Remarkably, by passivating the interstitials, alkalis make carrier lifetimes up to seven times longer than in defect‐free perovskites and up to thirty times longer than in defective perovskites. These phenomena arise due to a complex interplay of the unusual chemical, structural, electrostatic and quantum properties of halide perovskites. The detailed mechanistic understanding of the improvement of perovskite properties by alkali metal doping provides key insights for defect passivation strategies in perovskites for a broad range of solar and electro‐optic applications.
by Adam Jaffe,
Stephanie A. Mack,
Yu Lin,
Wendy Mao,
Jeffrey B. Neaton,
Hemamala Karunadasa
Layered Cu–Cl perovskites show an electronic conductivity of 10−4 S cm−1 only above 50 GPa. In contrast, an analogous Cu‐Br perovskite exhibits a conductivity as high as 10−3 S cm−1 at only 2.6 GPa. Substitution of Br for Cl brings compression‐induced conductivity of layered copper‐halide perovskites to more technologically accessible pressures.
Abstract
We show that the onset pressure for appreciable conductivity in layered copper‐halide perovskites can decrease by ca. 50 GPa upon replacement of Cl with Br. Layered Cu–Cl perovskites require pressures >50 GPa to show a conductivity of 10−4 S cm−1, whereas here a Cu–Br congener, (EA)2CuBr4 (EA=ethylammonium), exhibits conductivity as high as 2×10−3 S cm−1 at only 2.6 GPa, and 0.17 S cm−1 at 59 GPa. Substitution of higher‐energy Br 4p for Cl 3p orbitals lowers the charge‐transfer band gap of the perovskite by 0.9 eV. This 1.7 eV band gap decreases to 0.3 eV at 65 GPa. High‐pressure X‐ray diffraction, optical absorption, and transport measurements, and density functional theory calculations allow us to track compression‐induced structural and electronic changes. The notable enhancement of the Br perovskite's electronic response to pressure may be attributed to more diffuse Br valence orbitals relative to Cl orbitals. This work brings the compression‐induced conductivity of Cu‐halide perovskites to more technologically accessible pressures.
by Wei Meng†, Yi Hou†, Andre´ Karl†, Ening Gu†, Xiaofeng Tang†, Andres Osvet†, Kaicheng Zhang†, Yicheng Zhao†, Xiaoyan Du†, Jose´ Garcia Cerrillo†, Ning Li*†‡§, and Christoph J. Brabec*†‡
by Seyedeh Mozhgan Seyed‐Talebi,
Iraj Kazeminezhad,
Saeed Shahbazi,
Eric Wei‐Guang Diau
The nontoxic carbon spheres synthesized with uniform morphology and controllable size and used as a template to generate the tunable porous TiO2 films. The effect of porosity modification of TiO2 film, as an efficient ETL in the perovskite solar cells, on the formation of CH3NH3PbI3 films with large grain size is studied in ambient atmosphere with humidity higher than 50%.
Abstract
Crystallization and nucleation of the perovskite layer in the mesoscopic perovskite solar cells (PSCs) depend on the nucleation sites of the electron transport layer (ETL). The porosity optimization of TiO2 film as an efficient ETL plays an important role in the performance improvement of PSCs. In the present study, nontoxic carbon spheres synthesized with uniform morphology and controllable size under hydrothermal conditions and used as a template to generate the tunable porous TiO2 films. Furthermore, the effect of porosity modification of TiO2 on the formation of perovskite films with large grain size is studied in an ambient atmosphere with humidity higher than 50%. The best TiO2 film is produced with carbon spheres 8 wt% (C8), which results in the formation of a pinhole‐free, and compact‐packed perovskite layer. The fully air processed PSC device with the ETL made of C8 film exhibits an efficiency of 16.66% with reduced hysteresis, which is much superior in performance compared to the standard cell (11.72%). It is believed that this porosity optimization of TiO2 layer is a simple practical strategy for improved stability of fully air processed efficient perovskite solar cells and usable for the fabrication of reproducible compact perovskite layers in uncontrolled laboratories.
J. Mater. Chem. A, 2020, 8,1865-1874 DOI: 10.1039/C9TA12368G, Paper
Wei Chen, Guotao Pang, Yecheng Zhou, Yizhe Sun, Fang-Zhou Liu, Rui Chen, Shuming Chen, Aleksandra B. Djurišić, Zhubing He We demonstrate a substantial suppression of interfacial trap states in inverted PSCs via CdZnSeS QDs, leading to a large efficiency improvement. The content of this RSS Feed (c) The Royal Society of Chemistry
by Azat F. Akbulatov†, Lyubov A. Frolova†‡, Nadezhda N. Dremova†, Ivan Zhidkov§, Vyacheslav M. Martynenko†, Sergey A. Tsarev‡, Sergey Yu. Luchkin‡, Ernst Z. Kurmaev§?, Sergey M. Aldoshin†, Keith J. Stevenson‡, and Pavel A. Troshin*‡†
Inorganic cesium lead tri-bromine (CsPbBr3) perovskite is a star material in modern optoelectronic and electronic nanodevices due to its fascinating optical and electronic properties and excellent stability in atmosphere. However, the unique dielectric behavior still remains to be exploited. Herein, inorganic CsPbBr3 perovskite is introduced into triboelectric nanogenerators for the first time in view of its tremendous dielectric and electrical properties. Electron binding energy, dielectric properties and surface potentials are systematically optimized through doping Ba2+ into CsPbBr3 lattice to form CsPb1-xBaxBr3 (x = 0.01–0.13) perovskites. The output performances are significantly improved on account of enhanced space charge polarization and increased work function. An open-circuit voltage of 220 V, short-circuit current density of 22.8 mA m−2 and maximized power density of 3.07 W m−2 are registered by the champion CsPb0.91Ba0.09Br3 based TENG with lighting up over 80 LED lights. Finally, impacts of temperature and relative humidity on the output performance of perovskite TENG are investigated, high durability and stability of the perovskite TENGs are presented indicating the remarkable reversibility and adaptability of all-inorganic CsPbBr3 perovskites in TENG for mechanical energy harvesting.
by Hongwei Lei,
Pei Dai,
Xinran Wang,
Zongwei Pan,
Yaxiong Guo,
Huan Shen,
Jianjun Chen,
Jing Xie,
Bing Zhang,
Song Zhang,
Zuojun Tan
Tetraethyl orthosilicate processed silica oligomer is in situ introduced into perovskite films to serve as a passivation agent (PA) for perovskite solar cells (PVSCs). Silica oligomer PA can enlarge perovskite grain sizes, prolong carrier lifetime, enhance charge carrier dynamics, and reduce trap state densities, resulting in highly efficient PVSCs with good humid and thermal stability.
Abstract
Perovskite solar cells (PVSCs) have achieved excellent power conversion efficiency (PCE) but still suffer from instability issues. Defect passivation is an important route to simultaneously increase the efficiency and stability of PVSCs. Here, a strategy of incorporating silica oligomer in perovskite films for surface and grain boundary defect passivation is reported. Silica oligomer passivation agent (PA) is in situ formed through hydrolysis and condensation reaction of tetraethyl orthosilicate additive in perovskite precursor. The passivation mechanism is elucidated by density functional theory calculation, revealing stable chelating interaction and hydrogen bond interaction between PA and perovskite. Spectroscopic and electrical characterizations demonstrate that silica oligomer can enlarge grain sizes, prolong carrier lifetime, enhance charge carrier dynamics, and reduce trap state densities in perovskite films. Planar PVSCs with passivation achieve a highly improved PCE of 19.64% with a stabilized efficiency of 18.81%. More importantly, unencapsulated perovskite devices with passivation retain nearly 90% of original efficiency after 1000 h storage under ambient condition and sustained 87% of initial performance after high‐temperature (120 °C) thermal accelerated aging, showing highly enhanced moisture and thermal stability. Therefore, the present study provides a pathway to the future design and optimization of PVSCs with higher efficiency and greater stability.
The present study reveals a strong influence of sputtered NiOx on the perovskite crystallization and the appearance of residual PbI2 grains resulting in low photovoltaic device performance. Among different methylammonium (MA+) halide additives and vapor treatment (to improve the perovskite crystallization) only MA+ halide vapor‐treated perovskite shows suppressed recombination, enhanced carrier lifetime, and device efficiency.
Abstract
Investigating the low efficiency issue of radio frequency‐sputtered nickel oxide (sp‐NiOx)‐based perovskite solar cells (PSCs) due to a limited understanding of the correlation between perovskite growth and sp‐NiOx on the optoelectronic properties and photovoltaic device performance is critical. Herein, the crystallization of methylammonium (MA) lead iodide (MAPbI3) thin film (obtained from stoichiometric precursor ratio) on sp‐NiOx is shown, resulting in appearance of residual PbI2 grains. This is in contrast to perovskite growth on solution‐processed NiOx. The amount of residual PbI2 is suppressed by 1) adding excess MACl/MAI additives and 2) annealing the perovskite film in MACl/MAI vapor atmosphere. Structural and morphological results reveal significant reduction in the amount of residual PbI2 and enhanced grain size for all the cases while photophysical measurements reveal mitigation of trap/defect sites (within the bulk and at the interfaces) only for MACl/MAI vapor annealing case. As a result, photovoltaic devices exhibit improved performance only for the vapor annealing case. These results elucidate the critical role of maintaining stoichiometric ratio in perovskite and its crystallization on sp‐NiOx by eliminating the associated defects (influenced by sp‐NiOx) in rendering improved performance, which can be insightful to further enhance the performance of PSCs.
