A flexible self-powered UV–Vis photodetector based on Successive Ionic Layer Adsorption and Reaction (SILAR) deposited CdS on asymmetric contacts

Abstract

Self-powered photodetectors exhibiting broadband spectral responses have drawn significant attention owing to their zero-power consumption, high sensitivity, and enhanced light-matter interaction. However, considering the existing complex fabrication processes for self-powered devices, facile fabrication schemes that can be performed at room temperature and are scalable are highly desirable. This work demonstrates a metal-semiconductor-metal (MSM) based flexible, self-powered photodetector employing Successive Ionic Layer Adsorption and Reaction (SILAR) deposition of CdS directly on a paper substrate with interdigitated Asymmetric contacts, namely of pencil-drawn graphite and silver paste. Upon light illumination, a built-in field is generated due to the asymmetry in the fermi levels of the metal contacts, supporting efficient carrier separation. The as-fabricated device extends its absorbance from Ultraviolet (UV) to Visible (Vis) spectra, with the highest peak absorption around 520 nm. Further, the device exhibits a responsivity of 6.56 mA/W and 1500 mA/W and detectivity of 2.3 × 108 Jones and 5.66 × 1010 Jones when illuminated with Visible (intensity-0.0125 mW/cm2) and UV (intensity-2.50 mW/cm2) lights respectively. Without any external power, the device showed response times of 0.11 s and 1.42 s when subjected to UV and Vis irradiations. This detector also exhibited superior resistance to bending stress and retained its performance even after multiple bending cycles (∼1000). Hence, the facile, low-cost, and room-temperature SILAR deposition technique-assisted photodetector fabrication paves the way for developing other high-performance and flexible photodetectors for various optoelectronic applications.