Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 34, Pages 40489-40501Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c06533
Keywords
CsPbI2Br; charge trapping; defect passivation; [PbX6](4-) octahedron; stability
Funding
- State Key Program of the National Natural Science of China [U1906227]
- National Natural Science Foundation of China [51872171]
- Key Program of Natural Science Foundation of Shandong Province [ZR201801290005]
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The use of 4-GBACl small molecules effectively stabilizes CsPbI2Br perovskites, inhibits ion migration and charge trapping/recombination centers, and enhances the efficiency of solar cells.
Inorganic CsPbI2Br perovskites have witnessed incredible advances as a promising representative for translucent and tandem solar cells, but unfortunately, they are still plagued by serious energy losses and undesired phase instability. Herein, a new type of pi-conjugated small molecule of 4-guanidinobenzoic-acid-hydrochloride (4-GBACl) is demonstrated to effectively cross-link the Pb-X framework of perovskites. The strong coordination between 4-GBACl and the [PbX6](4-) octahedron of perovskites effectively stiffens the Pb-X framework to suppress the ion migration, thus stabilizing the perovskite phase structure against light and thermal conditions. Apart from the physical barrier for phase instability resulting from the hydrophobic benzene ring at grain boundaries (GBs), guanidinium cations and -COOH and Cl- groups can simultaneously afford the passivation of positively and negatively charged defects at the GBs and surface, including undercoordinated halide species and undercoordinated Pb2+ ions, thereby effectively inhibiting the charge trapping/recombination centers. Two-dimensional confocal-fluorescence mapping images provide a visualized sight into the significantly suppressed nonradiative recombination and the prolonged carrier lifetime. It is suggested that the 4-GBACl additive plays multiple roles in grain cross-linking to regulate crystallization, distinctly reducing the trapstate density, ion migration inhibition, and moisture barrier in CsPbI2Br films. Consequently, the 4-GBACl-treated device exhibits a champion power conversion efficiency (PCE) of 15.59% accompanied with a considerably improved V-oc of 1.28 V and maintains 88% of the initial PCE value after 1200 h aging under 20% relative humidity.
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