Ti0.87O2 nanosheets on Ni integrated n-Si: planar architecture with enhanced photoresponse for self-driven photodetectors

Abstract

Broadband, low-cost photodetectors are essential for low-power optoelectronic applications in communication, surveillance, robotics, and scientific research. While silicon photodetectors are cost-effective with mature processing, their indirect bandgap limits photoresponsivity and external quantum efficiency (EQE). Herein, we demonstrate a broadband, self-driven, high-efficiency photodetector via a Ti_0.87O₂ nanosheet/Ni/n-Si planar architecture. The integration of a Ni layer on n-Si enhances light absorption, generating hot electrons in it along with n-Si photoresponse. These excess hot carriers result in a thermoelectric potential required for self-driven high performance of the device. Additionally, dark current is suppressed by introducing bilayer Ti_0.87O₂ nanosheets between Ni and Ag through contact engineering. The proposed Ti_0.87O₂/Ni/n-Si device exhibits excellent self-driven performance with a photoresponsivity of 3.76 A W⁻¹, a detectivity of 2.02 × 10¹³ Jones and an on–off ratio of ∼10⁵% with 200 nm to the MIR detection range. Unprecedented EQE values of 1062% in the solar blind spectrum at 250 nm, 641% at 700 nm and 180% at 1000 nm illumination are also achieved, surpassing those of other Si-based photodetectors currently available. Under −5 V bias, the present device reveals an EQE of 2343% and a photoresponsivity of 8.91 A W⁻¹. The demonstrated architecture transcends traditional energy conversion Si limitations, unlocking the potential of next-generation optoelectronic devices with enhanced light harvesting capabilities.