Thermochromism to tune the optical bandgap of a lead-free perovskite-type hybrid semiconductor for efficiently enhancing photocurrent generation

Thermochromic materials have recently attracted great attention due to their controllable and rich physicochemical properties. However, until now, no studies have been reported on thermochromic materials for photovoltaic and optoelectronic applications. Here we report a new lead-free hybrid semiconductor material, (C16H20N2)SbBr5 (1), which adopts the zero-dimensional (0-D) perovskite-type inorganic framework. Strikingly, the thermochromism in 1 leads to a wide tunable bandgap and superior photoelectric properties. Three distinct color-varying stages were first observed, i.e. colorless to yellow (I), yellow to red (II), and red to black brown (III). In particular, the figure-of-merits for thin-film photodetectors based on II-thermochromism were greatly improved, with the dark current lowered to one quarter and light photocurrent enhanced at least 12-fold. The photocurrent on/off switching ratio was thus improved by similar to 50 times through thermochromism. As a new conceptual strategy to engineer the optical bandgap and meet specific photoelectric functions, our study paves the way for building high-performance optoelectronic devices based on thermochromic materials.