Wafer-Scale, Thickness-Controlled p-CuInSe₂/n-Si Heterojunction for Self-Biased, Highly Sensitive, and Broadband Photodetectors

The fabrication of wafer-scale, ultrathin, and highly sensitive p-CuInSe2/n-Si heterojunction photodetectors is demonstrated. CuInSe2 has been extensively utilized for photovoltaic applications owing to its excellent optoelectronic properties. Although the wafer-scale CuInSe2 photodetector fabrication and device-level demonstration are not well explored, it is of utmost importance to unveil the beneficial aspects of CuInSe2 by fabricating its wafer-scale heterojunction photodetectors. The wafer-scale CuInSe2 photodetectors are still underway, and the possible light management mechanism for various CuInSe2 thicknesses is underexplored. As a result, it is demanded to discover minimum and optimum CuInSe2 thickness for highly efficient wafer-scale photodetection. To serve this purpose, a strategy is projected to greatly increase the photodetection performance, possessing excellent sensitivity, broad spectral responsivity, and stability along with high speed. Our understanding demonstrates the capability to control the thickness parameter (from 436 to 43 nm) and alter the structural, optical, chemical, and optoelectronic characteristics of the p-CuInSe2 semiconductors in an unprecedented manner to attain the desired characteristics of photodetection performance. The maximum sensitivity, detectivity, and LDR, that is, 3.7 × 103, 0.61 × 1011 Jones, and 72 dB, respectively, are obtained under the halogen light for self-biased conditions. The highly efficient NIR response has been attained, and maximum sensitivity, responsivity, detectivity, and LDR, that is, 2.2 × 103, 158 A/W, 1.3 × 1012 Jones, and 79 dB at 980 nm, respectively, are obtained. The present work offers a sustainable approach for the wafer-scale uniform synthesis of ultrathin CuInSe2 (58 nm) for the development of self-biased, highly efficient, and broadband photodetectors.