An ultra-flexible silicon substrate with light-trapping structures: The application for visible-NIR photodetectors

Flexible substrates have been widely used in Visible-NIR photodetectors in recent years. Flexible silicon wafers were prepared by alkali etching. Pyramids with reflectivity of 11.8%, inverted pyramid with reflectivity of 7.9% and nanowire with reflectivity of 1.9% light-trapping structures were prepared by low concentration alkali etching, one-step Cu-MACE and Ag-MACE, respectively. In addition, PEDOT: PSS films doped with 5 wt% DMSO successfully presented the highest conductivity of 580 S·cm−1. The PEDOT: PSS/UF-Si PDs with different light-trapping structures were prepared by spin-coating PEDOT: PSS films. Comparing the optoelectronic performance of different light-trapping structures of the photodetector, the PEDOT: PSS/UF-Si NWs device exhibited the best optoelectronic performance. The photoresponse range is 300–1100 nm and the responsivity at the peak of 650 nm is 0.62 A·W−1. Furthermore, bending measurements are performed on PEDOT: PSS/UF-Si NWs PDs to evaluate the bending performance of the flexible PDs. For PEDOT: PSS/UF-Si NWs PDs with a bending radius of 5.3 mm and a bending cycle of 500, the responsitivity of the device demonstrates very small degradation.