Efficient Charge Separation in Polypyrrole/GaN-Nanorod-Based Hybrid Heterojunctions for High-Performance Self-Powered UV Photodetection

Abstract

The ozonosphere is infiltrated by UV-A rays (λ = 320–400 nm) that reach the Earth's atmosphere, posing serious health problems such as premature aging and skin cancer. Owing to the importance of UV-A ray detection, highly detective, novel, and high-speed UV-A photodetectors have recently attracted considerable attention. The integration of organic and inorganic hybrid structures yields highly attractive optoelectronic properties that make them attractive candidates for high-performance self-powered UV-A photodetectors. Herein, the integration of conductive polypyrrole (Ppy) and GaN nanorods for high-performance self-powered UV-A photodetectors is demonstrated. The device exhibits superior photoresponse properties such as detectivity, responsivity, and external quantum efficiency values as 5.0 × 1012 Jones, 102 A W−1, and 29.8 × 103%, respectively, at a power density of 1.32 mW cm−2 (λ = 382 nm) and zero bias, which are relatively higher than those of pristine GaN nanorods. Furthermore, the device exhibits good stability and reproducibility with fast rising (350 ms) and falling (410 ms) times. The high photoresponse is attributed to the large built-in potential formed at the interface junction of the Ppy and the GaN nanorods. Furthermore, the mechanism behind the high photoresponse is investigated using an X-ray photoelectron spectroscopy (XPS) analysis and energy band theory.