Wave-Interference Photonic Crystals and Space Charge Engineering Enable Efficient Broadband Faint Light Detection in Organic/Inorganic Hybrid Photodetectors

Abstract

Noise current, detectivity, quantum efficiency, and response speed are critical metrics in evaluating organic/inorganic photodiodes. Herein, these metrics are simultaneously advanced in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/native SiO_x/n-Si hybrid photodetectors, achieving excellent performance in detecting broadband faint light. Wave-interference photonic crystals, comprising periodic microstructured inverse pyramids with nanometer-scale mesa widths, are integrated into the Si absorber to effectively couple incident light for increased absorption, thereby balancing optics and conformal contact coverage. The developed photodetector comprises a deep depletion region and interfacial SiO_x layer, enabling diffusion-mitigated broadband photocarrier transport and effective charge collection, and suppressing carrier tunneling processes for low-noise. An ultralow reverse dark current density of ≈2.46 × 10⁻⁸ A cm⁻² at −0.4 V is realized for nanowatt-level light detection. The photodetector showcases superlative properties among reported PEDOT:PSS–based inorganic heterojunctions, including a broadband external quantum efficiency of >≈80% from 340 to 960 nm (internal quantum efficiency of >≈90% from 380 to 840 nm), detectivity of >≈10¹² Jones from 300 to 1140 nm, and microsecond response speed. This study provides practical insight for combining high-absorption microstructures with space charge engineering for the development of high-performance organic/inorganic hybrid photodetectors.