Diketopyrrolopyrrole organic cations as strategy for iodide and lead-free hybrid metal–halide based photoconductors

Abstract

For the next generation of photoconductors, hybrid molecular materials based on metal–halide anionic networks and electroactive organic cations of viologen type have been considered. Charge-transfer hybrid materials with reasonable (photo)conducting responses required the association to lead-iodide based inorganic components. Here, the benefit of using an organic divalent cation based on the diketopyrrolopyrrole (DPP) chromophore afforded a series of iodide-free and one example of lead-free photoconducting devices. Specifically, lead-chloride and lead-bromide compounds present an electronic structure of type I with frontier orbitals based solely on the organic cation, while the bismuth-bromide 1D perovskite network reveals a type II alignment with participation of both components to the charge transfer. The resulting devices show relevant photocurrent/dark current response ratios of up to 3.7 at 1.0 mW mm⁻², opening the strategy of DPP-based hybrid metal–halides for stable and non-toxic photoresponsive devices.