Transparent, Flexible Silicon Nanostructured Wire Networks with Seamless Junctions for High Performance Photodetector Applications.

Optically transparent photodetectors are crucial in next generation optoelectronic applications including smart windows and transparent image sensors. Designing photodetectors with high transparency, photoresponsivity and robust mechanical flexibility remains a significant challenge, as is managing the inevitable tradeoff between high transparency and strong photoresponse. Here we report a novel scalable method to produce flexible crystalline Si nanostructured wire (NW) networks fabricated from silicon-on-insulator (SOI) with seamless junctions and highly responsive porous Si segments that combine to deliver exceptional performance. These networks show high transparency (~ 92% at 550 nm), broadband photodetection (350 nm to 950 nm) with excellent responsivity (25 A/W), optical response time (0.58 ms) and mechanical flexibility (1000 cycles). Temperature dependent photocurrent measurements indicate the presence of localized electronic states in the porous Si segments, which play a crucial role in light harvesting and photo-carrier generation. The scalable low-cost approach based on SOI has the potential to deliver new classes of flexible optoelectronic devices, including next generation photodetectors and solar cells.