Giant Bulk Photovoltaic Effect in a Chiral Polar Crystal based on Helical One-dimensional Lead Halide Perovskites

Chiral polar crystals composed of one-dimensional (1D) conducting materials exhibit unique physical phenomena. The present study focused on helical 1D-structured lead halide perovskite derivatives with chiral naphthylethylamine as organic cations, (R or S-NEA)[PbI₃](R-NEA=R-(+)-1-(1-naphthyl)ethylamine, S-NEA=S-(-)-1-(1-naphthyl)ethylamine). A thermally controlled crystallization method has successfully yielded crystals with a polar chiral space group of C2. The crystals show significantly intense signals of circular dichroism (CD) originating from the asymmetrical electronic transition characteristic of helical 1D structure. In addition, generation of an anomalous zero-bias photocurrent (bulk photovoltaic effect (BPVE)) was observed with an open-circuit voltage up to 15 V, which is five times larger than the band gap. This study suggests that parallel arrangements of the helical semiconducting materials are the promising way to obtain chiral polar crystal exhibiting high performance BPVE.