Stable Photodetectors Based on Formamidinium Lead Iodide Quantum Well Perovskite Nanoparticles Fabricated with Excess Organic Cations

Metal halide perovskite nanoparticles have recently attracted immense interest for photodetectors due to their outstanding optical and electronic properties such as high carrier diffusion length, tunable band gap (light absorption range), and high photoluminescence (PL) efficiency. Although significant progress has been achieved in the development of perovskites, their stability is yet to be addressed. To improve the stability and quantum efficiency of FAPbI3 perovskite nanocrystals, we present a room temperature protocol to fabricate fully passivated and stable FAPbI3 nanocrystals via 2D growth in the presence of amine ligands and an excess amount of the organic cations. The crystallization mechanism of 2D colloidal quantum wells (QWs) with long-time stability is ascribed to the excess amount of large organic cations which isolate the inorganic lattice octahedral layers. It is demonstrated that the QW films (130 nm) hold 90% of their PL intensity after 30 days, which is ∼8 times more stable than FAPbI3 quantum dot (QD) films. We also show the enhanced photoresponsivity of QW photodetectors (up to 100%) as compared with QD devices. The long-term ambient performance of perovskite QW photodetectors on account of their hydrophobicity is demonstrated. The findings can shed light on a way to develop ambient stable QW nanoparticle perovskite optoelectronic devices.