Construction of chiral-2D/3D perovskite heterojunction films for efficient circularly polarized light detection

2D Ruddlesden–Popper perovskites with chiral organic ligands are emerging as promising candidates for circularly polarized light (CPL) detection, which has important applications in quantum communication and opto-spintronics. However, the insulating organic spacers in 2D perovskites generally hinder carrier transport and charge extraction, hence leading to a low responsivity of photodetectors. Herein, we have prepared a chiral-2D/3D perovskite heterojunction thin film via intermittent spin-coating of the chiral-2D ligands on top of a 3D perovskite film. The chiral-2D perovskite formed on top of the film functions as the CPL absorption layer, while the energy transfer between chiral-2D and 3D perovskites and the dissociation of excitons in the 3D phase facilitate the efficient lateral carrier transport and extraction in the bottom 3D perovskite-based charge transport channel. The resultant heterojunction CPL detectors exhibit a high anisotropy factor of 0.13 and a large specific detectivity of above 6.8 × 1010 Jones that significantly outperform those of the pure chiral-2D based ones, which paves the way for the design and preparation of high performance perovskite thin film-based CPL detectors.