Guanidinium-Assisted Surface Matrix Engineering for Highly Efficient Perovskite Quantum Dot Photovoltaics
Xufeng Ling,1 Jianyu Yuan,*1 Xuliang Zhang,1 Yuli Qian,1 Shaik M. Zakeeruddin,2 Bryon W. Larson,3 Qian Zhao,3 Junwei Shi,1 Jiacheng Yang,1 Kang Ji,1 Yannan Zhang,1 Yongjie Wang,1 Chunyang Zhang,2 Steﬀen Duhm,*1 Joseph M. Luther,3 Michael Grätzel,*2 and Wanli Ma*1
1Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123, P. R. China
2Laboratory of Photonics and Interfaces (LPI), Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL), Station 6, Lausanne CH-1015, Switzerland
3Chemistry & Nanoscience Center National Renewable Energy Laboratory, Golden, CO 80401, USA
Metal halide perovskite quantum dots (Pe-QDs) are of great interest in new-generation photovoltaics (PVs). However, it remains challenging in the construction of conductive and intact Pe-QD films to maximize their functionality. Herein, a ligand-assisted surface matrix strategy to engineer the surface and packing states of Pe-QD solids is demonstrated by a mild thermal annealing treatment after ligand exchange processing (referred to as “LE-TA”) triggered by guanidinium thiocyanate. The “LE-TA” method induces the formation of surface matrix on CsPbI3 QDs, which is dominated by the cationic guanidinium (GA+) rather than the SCN-, maintaining the intact cubic structure and facilitating interparticle electrical interaction of QD solids. Consequently, the GA-matrix-confined CsPbI3 QDs exhibit remarkably enhanced charge mobility and carrier diﬀusion length compared to control ones, leading to a champion power conversion efficiency of 15.21% when assembled in PVs, which is one of the highest among all Pe-QD solar cells. Additionally, the “LE-TA” method shows similar eﬀects when applied to other Pe-QD PV systems like CsPbBr3 and FAPbI3 (FA = formamidinium), indicating its versatility in regulating the surfaces of various Pe-QDs. This work may aﬀord new guidelines to construct electrically conductive and structurally intact Pe-QD solids for efficient optoelectronic devices.