Self-Powered and Fast Response MoO₃/n-Si Photodetectors on Flexible Silicon Substrates with Light-Trapping Structures

Flexible photodetectors are considered to be extremely important flexible electronic components of the future. In this work, flexible silicon (F-Si) substrates with inverted pyramidal light-trapping structures were prepared by wet chemistry and metal-assisted etching. Due to the better ability of the light-trapping structure to capture light, the F-Si substrate was capable of absorbing more than 90% of visible light and can be in bending angles of over 180°. On the basis of F-Si substrates with light-trapping structures, self-powered MoO3/n-Si heterojunction flexible photodetectors (FPDs) were prepared to achieve high responsivity (0.696 A/W@980 nm), detectivity (1.59 × 1013 jones), and fast response (τr/τd of 5.35 μs/0.97 μs). The devices also showed effective photoresponse in the wavelength range from 405 to 980 nm. Moreover, the Si-based FPDs exhibited a favorable response to high-frequency light, with a response frequency of up to 100 kHz. The photocurrent of the device maintained more than 95% of the initial value after 200 bending cycles. In addition, Si-based FPDs are successfully applied to fingertip heartbeat tests for human health data extraction. The development of Si-based FPDs provides a path for flexible electronic devices.