CuInSe₂ Quantum Dot-Coated Silicon Nanowire Photodetectors with Enhanced NIR Responsivity

Silicon nanowire (SiNW)-based photodetectors (PDs) offer enhanced light trapping but suffer from limited near-infrared (NIR) responsivity near the silicon bandgap edge. Here, we demonstrate a CuInSe₂ (CISe) quantum dot (QD)-coated SiNW PD that significantly enhances NIR photoresponse through heterojunction engineering. CISe QDs were synthesized via a hot-injection method and subsequently subjected to inorganic ligand exchange using methylammonium iodide and tin (IV) iodide (SnI₄) to improve interparticle charge transport. The CISe QD layer was conformally deposited onto the SiNW array via spray coating. The fabricated devices exhibit a peak responsivity of 0.543 A/W at 880 nm and a peak external quantum efficiency of 78.3% at 820 nm, outperforming bare SiNW PDs across the 700-1000 nm range. The enhanced performance is attributed to reduced surface reflectance and efficient carrier separation enabled by type-II band alignment at the n-Si/CISe interface. These results demonstrate a viable strategy for environmentally friendly, solution-processable NIR PDs compatible with silicon platforms.