期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 121, 期 22, 页码 12110-12116出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.7b04543
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We present an investigation of the ultrafast charge carrier dynamics for the one-third metal-deficient lead-free perovskite (CH3NH3)(3)Bi2I9 on mesoporous TiO2. Excitation of the perovskite at 400 or 505 nm leads to characteristic second derivative-type spectral features in the transient absorption spectra, suggesting substantial contributions of bound excitons, in contrast to the widely used lead-based perovskites. The immediate appearance of broad NIR absorption is assigned to TiO2 conduction band electrons formed by instantaneous dissociation of a subpopulation of excitons at the perovskite/TiO2 interface. Excitation with excess energy above the perovskite's band gap opens up an additional fast (70 fs) exciton dissociation channel with about 26% amplitude. Antisolvent-assisted synthesis of (CH3NH3)(3)Bi2I9 reduces the crystallite size to about 500 nm but has only a minor effect on the carrier dynamics. The results suggest that photovoltaic applications require bulk-heterojunction architectures to efficiently split the excitons into free carriers. of this material will likely
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