Diketopyrrolopyrrole organic cations as strategy for iodide and lead-free hybrid metalhalide 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 2 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, opening the strategy of DPP-based hybrid metal-halides for stable and non-toxic photoresponsive devices.