Perovskite Quantum Wells Formation Mechanism for Stable Efficient Perovskite Photovoltaics—A Real‐Time Phase‐Transition Study. Issue 7 (29th December 2020)

• Record Type: Journal Article
• Authors: Hu, Hanlin; Qin, Minchao; Fong, Patrick W. K.; Ren, Zhiwei; Wan, Xuejuan; Singh, Mriganka; Su, Chun‐Jen; Jeng, U‐Ser; Li, Liang; Zhu, Jiajie; Yuan, Mingjian; Lu, Xinhui; Chu, Chih‐Wei; Li, Gang
• Is Part Of: Advanced materials. Volume 33:Issue 7(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-29
• Subjects: perovskite photovoltaics -- perovskite quantum wells -- phase‐transitions; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202006238
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: The combination of a bulk 3D perovskite layer and a reduced dimensional perovskite layer (perovskite quantum wells (PQWs)) is demonstrated to enhance the performance of perovskite solar cells (PSCs) significantly in terms of stability and efficiency. This perovskite hierarchy has attracted intensive research interest; however, the in‐depth formation mechanism of perovskite quantum wells on top of a 3D perovskite layer is not clearly understood and is therefore the focus of this study. Along with ex situ morphology and photophysical characterization, the time‐resolved grazing‐incidence wide‐angle X‐ray scattering (TS‐GIWAXS) technique performed in this study provides real‐time insights on the phase‐transition during the organic cation (HTAB ligand molecule) coating and PQWs/3D architecture formation process. A strikingly strong ionic reaction between the 3D perovskite and the long‐chain organic cation leads to the quick formation of an ordered intermediate phase within only a few seconds. The optimal PQWs/3D architecture is achieved by controlling the HTAB casting, which is assisted by time‐of‐flight SIMS characterization. By controlling the second ionic reaction during the long‐chain cation coating process, along with the fluorinated poly(triarylamine) (PTAA) as a hole‐transport layer, the perovskite solar cells demonstrate efficiencies exceeding 22% along with drastically improved device stability. Abstract : The time‐resolved grazing‐incidence wide‐angle X‐ray scattering technique provides real‐time insights on the phase‐transition during the organic cation coating and perovskite quantum wells (PQWs)/3D architecture formation mechanism. With fluorinated poly(triarylamine) (PTAA) as a dopant‐free hole‐transport layer, this PQWs/3D architecture leads to stable perovskite photovoltaics with power conversion efficiency of >22%.