Cui Yunkang, Chen Cong, Li Chongwen, Chen Lei, Bista Sandip Singh, Liu Xiangyang, Li You, Awni Rasha A, Song Zhaoning, Yan Yanfa
Wright Center for Photovoltaics Innovation and Commercialization, Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606, United States.
Department of Mathematics and Physics, Nanjing Institute of Technology, Nanjing 211167, China.
ACS Appl Mater Interfaces. 2020 Mar 4;12(9):10588-10596. doi: 10.1021/acsami.9b23374. Epub 2020 Feb 24.
The two-step solution-based process has demonstrated substantial success in fabricating high-efficiency perovskite solar cells in recent years. Despite the high performance, the underlying mechanisms that govern the formation of perovskite films and corresponding device performance are yet to be fully understood. Particularly, organic cation composition used in the two-step solution processing of mixed-cation lead halide perovskite solar cells plays a critical role in the perovskite film formation and the resultant device performance. However, little is understood about the impacts of organic cation composition on the current density-voltage (-) hysteretic behavior and stability of perovskite solar cells. To address this need, here, we study the effect of mixed organic cations, that is, the fraction of formamidinium (FA) and methylammonium (MA) contents, used for the two-step solution-processed perovskite thin films on solar cell performance, including efficiency, - hysteresis, and stability. In addition to the efficiency variations, we find that perovskite solar cells based on FA-rich and MA-rich stoichiometries show distinct characteristics in - hysteresis and stability. The origins of such a discrepancy are attributed to the thermodynamically driven conversion from lead iodide to perovskites, which is determined by the combination of organic cations. The perovskite solar cells based on the mixed cation FAMAPbI composition show a champion power conversion efficiency of over 21% and robust stability (retaining more than 90% of initial efficiency) under maximum power-point tracking in dry nitrogen for more than 500 h. Our work provides insights on understanding the formation of perovskite films in the two-step process, which may benefit further investigation on perovskite solar cells.
近年来，基于溶液的两步法在制备高效钙钛矿太阳能电池方面取得了显著成功。尽管性能优异，但支配钙钛矿薄膜形成及相应器件性能的潜在机制仍未完全明了。特别是，混合阳离子卤化铅钙钛矿太阳能电池两步溶液处理中使用的有机阳离子组成，在钙钛矿薄膜形成和最终器件性能方面起着关键作用。然而，关于有机阳离子组成对钙钛矿太阳能电池电流密度 - 电压（J - V）滞后行为和稳定性的影响，人们了解甚少。为满足这一需求，在此我们研究了用于两步溶液处理的钙钛矿薄膜的混合有机阳离子，即甲脒（FA）和甲铵（MA）含量的比例，对太阳能电池性能的影响，包括效率、J - V滞后和稳定性。除了效率变化外，我们发现基于富FA和富MA化学计量比的钙钛矿太阳能电池在J - V滞后和稳定性方面表现出不同的特性。这种差异的根源归因于由有机阳离子组合决定的从碘化铅到钙钛矿的热力学驱动转变。基于混合阳离子FAMAPbI组成的钙钛矿太阳能电池在干燥氮气中最大功率点跟踪下超过500小时，显示出超过21%的冠军功率转换效率和强大的稳定性（保持初始效率的90%以上）。我们的工作为理解两步法中钙钛矿薄膜的形成提供了见解，这可能有助于对钙钛矿太阳能电池的进一步研究。
