Enhancing photodetection performance and thermal tolerance of CdS thin films through cobalt (Co) doping

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 × 10${}^6$%), 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. (© 2023 Wiley‐VCH GmbH)