Preparation And Performance Of Perovskite Solar Cells Based On Low Temperature Metal Oxide Electron Transport Layers

Perovskite solar cells have developed rapidly since their appearance in 2009due to the excellent optical and electrical properties of perovskite materials.Nowadays,perovskite solar cells based on low-temperature metal oxide?Ti O₂,ZnO,SnO₂,etc.?electron transport layers?ETLs?have gradually attracted the attention of researchers due to their lower manufacturing costs and easier implementation of flexible devices.This work focuses on the study of low temperature electron transport layers for perovksite solar cells.The main research contents and results are as follows:?1?A simple and effective method has been developed to improve the stability of ZnO-based perovskite solar cells.ZnO nanoparticle?NP?-or ZnO sol-gel layers capped with low-temperature processed TiO₂,namely ZnO/TiO₂bilayered films,were employed as ETLs in MAPbI₃-based perovskite solar cells.The results show that these Zn O/TiO₂ bilayered ETLs can not only improve the stability of perovskite films,but also improve the photovoltaic performance of devices compared with ZnO single-layer ETLs.Devices based on ZnO/TiO₂bilayered ETLs achieve a maximum efficiency of 15%,and nearly maintain its initial efficiency of 100%after 30 days of atmosphere storage,outperformed obviously those based on ZnO single-layer ETLs in both device performance and stability.Moreover,it is found that perovskite films and devices prepared on the single Zn O sol-gel ETLs are much superior to those deposited on the single ZnO NP-ETLs in both stability and performance,which can be ascribed to less surface hydroxyl groups and much smoother surface morphology of the ZnO sol-gel films.?2?The performance of perovskite solar cells prepared on three low-temperature electron transport layers?namely,TiO₂,ZnO and Sn O₂?using identical perovskite deposition method were compared directly and analyzed from the aspects of film morphology,optical and electrical properties.It is concluded that SnO₂ is the best low-temperature electron transport material among them.The possible reasons are as follows:in comparison with ZnO and TiO₂,SnO₂ electron transport layer has a deeper conduction band minimum and higher electrical conductivity,which facilitate the injection and transport of photo-generated electrons;moreover,the perovskite film deposited on SnO₂ has the strongest light absorption and larger crystal grain size,and the device based on Sn O₂ has the lowest series resistance and the highest parallel resistance,all of which result in the highest J_sc,FF and PCE for devices based on Sn O₂.In addition,compared with perovskite solar cells based on ZnO/TiO₂ and conventional high-temperature TiO₂ electron transport layers,the as-prepared low-temperature SnO₂-based perovskite solar cells have similar or higher power conversion efficiency.And when?FAPbI₃?_0.97?MAPbBr₃?_0.03.03 is used as the light absorption layer,an almost hysteresis-free SnO₂-based perovskite solar cell with an efficiency up to 15.80%was achieved,indicating that Sn O₂ is a very promising low-temperature metal oxide electron transport material.At the same time,it is found that the hysteresis phenomenon of cells is related to both electron transport layer and perovskite layer.