Dual-source vapor-processed blue-emissive cesium copper iodine microplatelets with high crystallinity and stability

Abstract

Recently, hybrid lead-halide perovskites have attracted extensive attention because of their unique optoelectronic characteristics, such as ambipolar charge transport, tunable bandgap, high carrier mobility, low-temperature processing technique, and so on. However, due to the poor stability and lead toxicity of conventional perovskites, their practical applications and future commercialization are greatly hindered. In this study, all-inorganic lead-free Cs₃Cu₂I₅ microplatelets (MPs) with high crystallinity and stability were successfully synthesized by a dual-source vapor deposition method for the first time. We investigated the effect of growth temperature, pressure and distance between the substrate and sources on the morphology and crystallinity of the MPs in detail. Different from the traditional lead-halide perovskites, the prepared Cs₃Cu₂I₅ MPs show an excellent stability against ultraviolet light irradiation (∼60 h), oxygen/moisture (2 months), and heat (300–373 K, 30 cycles). In addition, the Cs₃Cu₂I₅ MPs demonstrate excellent optical characteristics, including a wide bandgap of 3.87 eV, broadband blue emission, large Stokes shift, and strong electron–phonon coupling. It is anticipated that the above results obtained will provide valuable information for the preparation of non-toxic, stable, and highly crystallized Cs₃Cu₂I₅ MPs that can be employed in environment-friendly and reliable optoelectronic devices, such as deep ultraviolet photodetectors and blue light-emitting diodes.