The precursor-compensation strategy boosts the photoresponse performance of air-stable, self-powered Cs2SnI6 photodetectors

Abstract

Lead-free metal halide perovskites have attracted extensive attention as promising optoelectronic semiconductors with environmental friendliness. Cs₂SnI₆, a double perovskite with both a good phase and composition stability, is an appealing candidate for potential application in optoelectronic devices. To date, few reports have focused on the facile fabrication of dense and uniform Cs₂SnI₆ films that are key components for optoelectronic devices. Herein, a simple and low-cost solution method is reported to prepare densely packed Cs₂SnI₆ thin films. It was found that strategic precursor-compensation treatment (PCT) of the as-prepared spin-coated Cs₂SnI₆ thin films compensates the evaporation loss of volatile SnI₄ and thus allows for pinhole-free and pure-phase double perovskite. The modified n-type Cs₂SnI₆ double perovskite shows enhanced conductivity and mobility with decreased charge recombination loss. As a result, the applied photodetectors show an enhanced photocurrent gain of 151 compared to that of 88 for the control sample. The responsivity (control 0.0059 mA W⁻¹ to target 1.07 mA W⁻¹) and detectivity (control 2.94 × 10¹⁰ Jones to target 6.03 × 10¹⁰ Jones) of the device were significantly improved in the self-powered mode. In addition, the PCT-Cs₂SnI₆ photodetectors show excellent long-time stability with 98% initial detectivity retained after storing in ambient environment for 28 days. This study paves the way for the preparation of high-quality Cs₂SnI₆ films for application in efficient optoelectronic devices.