Enhancing Photodetection Performance and Thermal Tolerance of CdS Thin Films through Cobalt (Co) Doping

Abstract

A visible light photodetector is developed using cobalt (Co)‐doped cadmium sulfide (CdS) thin films that exhibits outstanding characteristics with a photocurrent of 284 μA, responsivity of 13.2 A W−1, an extraordinary external quantum efficiency (EQE) of 4550%, exceptional sensitivity (2.84 × 106%), and a rapid response time of 0.6 ms. These remarkable properties are most pronounced in 1 wt% Co‐doped CdS device and decrease with higher Co doping concentrations. This enhanced performance is attributed to the introduction of a defect energy band (DEB) near the CdS valence band, supported by UV‐Vis absorption spectra with a distinct feature at 744 nm. This DEB remains fully populated at room temperature and plays a vital role in responding to temperature variations. Our investigation reveals that 1 wt% Co‐doped CdS device exhibits significant (90%) thermal tolerance compared to pure CdS (10%) and higher Co doping concentrations (20%) in the temperature range of 27–110 °C. This improved thermal stability is attributed to the optimal Co doping concentration, striking a balance between thermal and photo‐excitation processes, thereby stabilizing the photocurrent. This research offers valuable insights into Co‐doped CdS thin films, promising robust and reliable photodetection devices, particularly suitable for applications with fluctuating temperatures.