Fe2O3-Mediated Photocurrent Modulation Effect for Enhanced Selective Detection in Organic Photodiode

Abstract

Organic photodetectors make great progress because they enable excellent sensitivity and narrow response through molecular structure control. This study explores the uniform Fe₂O₃ formed by atomic layer deposition in the development of organic photodiodes aimed at photocurrent with large variations in reverse bias condition. Fe₂O₃, a semiconducting oxide with an indirect band gap, was fabricated at various thicknesses to minimize high-charge recombination. The short lifespan of photogenerated charge carriers and limited hole diffusion length in Fe₂O₃ under green light illumination conditions provide light selectivity by counteracting the photogenerated charge carriers in the active layer. J–V characteristics revealed that diodes with a 3 nm Fe₂O₃ layer significantly reduced dark currents and exhibited modulation behavior, unlike the photodiode behavior exhibited with the use of thicker Fe₂O₃ layers. The built-in electric field at the ITO/Fe₂O₃ interface prevents photocurrents below a certain voltage, aiding the modulation behavior. Detectivity in blue and infrared regions was improved owing to selective photocurrents and reduced dark currents compared with the broad photosensitivity of PEDOT:PSS-based devices. This study suggests an efficient pathway for photocurrent modulation of the diode with the existing active layer by introducing Fe₂O₃.