Gelation of Hole Transport Layer to Improve the Stability of Perovskite Solar Cells

Ying Zhang; Chenxiao Zhou; Lizhi Lin; Fengtao Pei; Mengqi Xiao; Xiaoyan Yang; Guizhou Yuan; Cheng Zhu; Yu Chen; Qi Chen

doi:10.1007/s40820-023-01145-y

Gelation of Hole Transport Layer to Improve the Stability of Perovskite Solar Cells

Nanomicro Lett. 2023 Jul 10;15(1):175. doi: 10.1007/s40820-023-01145-y.

Authors

Ying Zhang¹, Chenxiao Zhou¹, Lizhi Lin¹, Fengtao Pei¹, Mengqi Xiao¹, Xiaoyan Yang¹, Guizhou Yuan¹, Cheng Zhu¹, Yu Chen¹, Qi Chen²

Affiliations

¹ Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China.
² Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China. qic@bit.edu.cn.

Abstract

To achieve high power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs), a hole transport layer (HTL) with persistently high conductivity, good moisture/oxygen barrier ability, and adequate passivation capability is important. To achieve enough conductivity and effective hole extraction, spiro-OMeTAD, one of the most frequently used HTL in optoelectronic devices, often needs chemical doping with a lithium compound (LiTFSI). However, the lithium salt dopant induces crystallization and has a negative impact on the performance and lifetime of the device due to its hygroscopic nature. Here, we provide an easy method for creating a gel by mixing a natural small molecule additive (thioctic acid, TA) with spiro-OMeTAD. We discover that gelation effectively improves the compactness of resultant HTL and prevents moisture and oxygen infiltration. Moreover, the gelation of HTL improves not only the conductivity of spiro-OMeTAD, but also the operational robustness of the devices in the atmospheric environment. In addition, TA passivates the perovskite defects and facilitates the charge transfer from the perovskite layer to HTL. As a consequence, the optimized PSCs based on the gelated HTL exhibit an improved PCE (22.52%) with excellent device stability.

Keywords: Aggregation of LiTFSI; Gelation; Hole transport layer; Humidity stability; Perovskite solar cell.