Phase Engineering of Perovskite Materials for High-Efficiency Solar Cells: Rapid Conversion of CH3NH3PbI3 to Phase-Pure CH3NH3PbCl3 via Hydrochloric Acid Vapor Annealing Post-Treatment

Weiran Zhou; Pengcheng Zhou; Xunyong Lei; Zhimin Fang; Mengmeng Zhang; Qing Liu; Tao Chen; Hualing Zeng; Liming Ding; Jun Zhu; Songyuan Dai; Shangfeng Yang

doi:10.1021/acsami.7b15008

Phase Engineering of Perovskite Materials for High-Efficiency Solar Cells: Rapid Conversion of CH₃NH₃PbI₃ to Phase-Pure CH₃NH₃PbCl₃ via Hydrochloric Acid Vapor Annealing Post-Treatment

ACS Appl Mater Interfaces. 2018 Jan 17;10(2):1897-1908. doi: 10.1021/acsami.7b15008. Epub 2018 Jan 5.

Authors

Affiliations

¹ Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Materials for Energy Conversion, Chinese Academy of Sciences, Department of Materials Science and Engineering, Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China (USTC) , Hefei 230026, China.
² ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, University of Science and Technology of China (USTC) , Hefei 230026, China.
³ National Center for Nanoscience and Technology , Beijing 100190, China.
⁴ Key Laboratory of Special Display Technology, Ministry of Education, National Engineering Laboratory of Special Display Technology, State Key Laboratory of Advanced Display Technology, Academy of Opto-Electronic Technology, Hefei University of Technology , Hefei 230009, China.
⁵ Beijing Key Laboratory of Novel Thin-Film Solar Cells, North China Electric Power University , Beijing 102206, China.

PMID: 29271198
DOI: 10.1021/acsami.7b15008

Abstract

Organometal halide CH₃NH₃PbI₃ (MAPbI₃) has been commonly used as the light absorber layer of perovskite solar cells (PSCs), and, especially, another halide element chlorine (Cl) has been often incorporated to assist the crystallization of perovskite film. However, in most cases, a predominant MAPbI₃ phase with trace of Cl^- is obtained ultimately and the role of Cl involvement remains unclear. Herein, we develop a low-cost and facile method, named hydrochloric acid vapor annealing (HAVA) post-treatment, and realize a rapid conversion of MAPbI₃ to phase-pure MAPbCl₃, demonstrating a new concept of phase engineering of perovskite materials toward efficiency enhancement of PSCs for the first time. The average grain size of perovskite film after HAVA post-treatment increases remarkably through an Ostwald ripening process, leading to a denser and smoother perovskite film with reduced trap states and enhanced crystallinity. More importantly, the generation of MAPbCl₃ secondary phase via phase engineering is beneficial for improving the carrier mobility with a more balanced carrier transport rate and enlarging the band gap of perovskite film along with optimized energy level alignment. As a result, under the optimized HAVA post-treatment time (2 min), we achieved a significant enhancement of the power conversion efficiency (PCE) of the MAPbI₃-based planar heterojunction-PSC device from 14.02 to 17.40% (the highest PCE reaches 18.45%) with greatly suppressed hysteresis of the current-voltage response.

Keywords: gas−solid reaction; organometal halide; perovskite solar cells; phase engineering; vapor annealing.