Efficient, Hysteresis‐Free, and Stable Perovskite Solar Cells with ZnO as Electron‐Transport Layer: Effect of Surface Passivation

• Published in: Advanced materials (Weinheim) Vol. 30; no. 11
• Main Authors: Cao, Jing, Wu, Binghui, Chen, Ruihao, Wu, Youyunqi, Hui, Yong, Mao, Bing‐Wei, Zheng, Nanfeng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2018
• Subjects: Chemical compatibility; Electron transport; Electrons; electron‐transport layer; Energy conversion efficiency; Hysteresis; hysteresis‐free; interface engineering; Interface stability; Magnesium oxide; Materials science; Passivity; perovskite solar cells; Photovoltaic cells; Solar cells; Zinc oxide; ZnO; ZnO; hysteresis-free; electron-transport layer; perovskite solar cells; interface engineering
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201705596

The power conversion efficiency of perovskite solar cells (PSCs) has ascended from 3.8% to 22.1% in recent years. ZnO has been well‐documented as an excellent electron‐transport material. However, the poor chemical compatibility between ZnO and organo‐metal halide perovskite makes it highly challenging to obtain highly efficient and stable PSCs using ZnO as the electron‐transport layer. It is demonstrated in this work that the surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine (EA) readily makes ZnO as a very promising electron‐transporting material for creating hysteresis‐free, efficient, and stable PSCs. Systematic studies in this work reveal several important roles of the modification: (i) MgO inhibits the interfacial charge recombination, and thus enhances cell performance and stability; (ii) the protonated EA promotes the effective electron transport from perovskite to ZnO, further fully eliminating PSCs hysteresis; (iii) the modification makes ZnO compatible with perovskite, nicely resolving the instability of ZnO/perovskite interface. With all these findings, PSCs with the best efficiency up to 21.1% and no hysteresis are successfully fabricated. PSCs stable in air for more than 300 h are achieved when graphene is used to further encapsulate the cells. Surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine readily makes ZnO a very promising electron‐transporting material for creating efficient, hysteresis‐free and stable perovskite solar cells (PSCs). PSCs, stable in air for more than 300 h, are achieved when graphene is used to encapsulate the cells.