Fabrication and characterization of self-powered SnO2/CdTe1-xSex/CdTe photodetectors

Abstract

This study presents the self-powered photodetector capabilities of fluorinated tin oxide (FTO)/CdTe₁₋ₓSeₓ/CdTe heterostructures with Se compositions of x = 0.26 and x = 0.39. Structural analysis revealed that substituting Se atoms into Te sites reduced the unit cell volume, indicating successful incorporation. Scanning Electron Microscopy (SEM) analysis demonstrated a significant reduction in surface feature size with increasing Se content, particularly at x = 0.39. Band gap determination via Tauc plot extrapolation showed a band gap of 1.46 eV for CdTe₁₋ₓSeₓ with x = 0.26, which further decreased to 1.38 eV for x = 0.39. Under illumination from blue, green, and red lights at zero bias, the heterostructures exhibited photovoltaic behavior, confirming their potential use as self-powered photodetectors (PDs). Key performance metrics at zero bias for the FTO/CdTe₁₋ₓSeₓ/CdTe device included a responsivity (R) of 0.006 A/W, detectivity (D*) of 1.1 × 10⁸ Jones, and external quantum efficiency (EQE) of 1.8%, along with the rise and fall times of 17 ms and 21 ms, respectively. Applying an external bias further enhanced these metrics, with the highest R of 2.301 A/W and EQE of 645.3% observed for the x = 0.26 sample at 1 V. Notably, the device with x = 0.39 achieved the highest D* of 2.2 × 10⁹ Jones at 1 V. In conclusion, this work highlighted the potential of FTO/CdTe₁₋ₓSeₓ/CdTe heterostructures as highly efficient and versatile photodetectors, capable of functioning both with and without an external power source, making them promising candidates for next-generation optoelectronic applications.