Details

Autor(en) / Beteiligte

• Qin, Minchao
• Tse, Kinfai
• Lau, Tsz‐Ki
• Li, Yuhao
• Su, Chun‐Jen
• Yang, Guang
• Chen, Jiehuan
• Zhu, Junyi
• Jeng, U‐Ser
• Li, Gang
• Chen, Hongzheng
• Lu, Xinhui

Titel

Manipulating the Mixed‐Perovskite Crystallization Pathway Unveiled by In Situ GIWAXS

Ist Teil von

• Advanced materials (Weinheim), 2019-06, Vol.31 (25), p.e1901284-n/a

Ort / Verlag

Germany: Wiley Subscription Services, Inc

Erscheinungsjahr

2019

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. Here, the detailed crystallization process of mixed perovskites (FA0.83MA0.17Pb(I0.83Br0.17)3) during spin‐coating is revealed by in situ grazing‐incidence wide‐angle X‐ray scattering measurements, and three phase‐formation stages are identified: I) precursor solution; II) hexagonal δ‐phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI–PbI2–DMSO intermediate phases, and perovskite α‐phase. The correlated device performance and ex situ characterizations suggest the existence of an “annealing window” covering the duration of stage II. The spin‐coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs+ ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs+ will bypass the formation of secondary phases in stage III by promoting the formation of α‐phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed‐perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance. The crystallization pathways of mixed perovskites under spin‐coating are investigated via in situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), which reveals the existence of an “annealing window”. The as‐cast film should be timely annealed within the annealing window to achieve a high‐quality perovskite film. The incorporation of Cs+ can remarkably extend the annealing window, thereby improving the device performance and reproducibility.