Investigation on Film Quality and Photophysical Properties of Narrow Bandgap Molecular Semiconductor Thin Film and Its Solar Cell Application.

Hexane-1,6-diammonium pentaiodobismuth (HDA-BiI₅) is one of the narrowest bandgap molecular semiconductor reported in recent years. Through the study of its energy band structure, it can be identified as an N-type semiconductor and is able to absorb most of the visible light, making it suitable to fabricate solar cells. In this paper, SnO₂ was used as an electron transport layer in HDA-BiI₅-based solar cells, for its higher carrier mobility compared with TiO₂, which is the electron transport layer used in previous researches. In addition, the dilution ratio of SnO₂ solution has an effect on both the morphology and photophysical properties of HDA-BiI₅ films. At the dilution ratio of SnO₂:H₂O = 3:8, the HDA-BiI₅ film has a better morphology and is less defect inside, and the corresponding device exhibited the best photovoltaic performance. [ABSTRACT FROM AUTHOR]