Large Grains and Shallow Defect States by Early Crystal Growth Suppression for High Responsivity in Perovskite Photodetectors

Abstract

The perovskite grain growth mechanism is a key factorto be consideredfor the enhancement of the photovoltaic effect in efficient self-poweredperovskite photodetectors (PDs). Among processes employed in morphologyengineering strategies, the washing process selectively removes polarsolvents, induces nucleation, and promotes the formation of intermediateperovskite phases. In this study, by exploiting on the LaMer mechanismand Weimarn theory, the washing solvent in the washing process iscontrolled for large perovskite grains. Efficient photodetectors sensitiveto a wide range of visible light are developed using a low-densitywashing solvent, namely ethyl ether, which maintains a low degreeof nucleation and delays crystal growth leading to the expansion ofperovskite grains. Perovskite processed with ethyl ether suppressesdark current and increases the photocurrent. Notably, the suppressionof early crystal growth contributes to the enhancement of specificdetectivity under self-powered operation. The proposed method forcontrolling nucleation and perovskite growth can be used to develophighly sensitive image sensors in smart vehicles via self-poweredPDs due to reduction of fuel loss. Nucleationand growth step induced by washing solvent isexplained through theoritical approach. Early crystal growth resultsfrom high degree of supersaturation due to high-density solvents.Ethyl ether-processed perovskite photodetectors reveal higher specificdetectivity under self-powered operation. Ethyl ether suppresses chargeinjection in the perovskite owing to assistance of grain expansionand shallow defect states.