Intrinsic Trapping and Recombination Dynamics in Low‐Dimensional Bismuth Sulfide Nanocrystals

Abstract Bismuth sulfide (Bi 2 S 3 ) possesses bandgap of 1.30–1.45 eV, perfectly suitable for light‐harvesting materials in solar cells. Carrier dynamics in the Bi 2 S 3 absorber material are determinant for energy conversion performance of solar cells, yet the carrier dynamics and associated recombination mechanism are rarely studied. Taking advantage of spectroscopic study on Bi 2 S 3 nanocrystals, here new findings are uncovered inherent from the unique crystal structure that causes the energy loss in Bi 2 S 3 materials. One is the trap state emission at near‐infrared region, the other is the ultrafast intrinsic trapping in picosecond scale without saturation at 10 19 cm −3 carrier density and various decay rates by adjusting excitation fluence. These observations indicate that photoinduced carriers are likely to be intrinsically trapped due to lattice distortion and display different recombination pathways. This study provides fundamental understanding on the detailed carriers dynamics of Bi 2 S 3 nanocrystals and new insights into the optimization of Bi 2 S 3 ‐based photovoltaic devices.