High Performance Flexible Graphene‐Silicon Heterojunction Photodetectors Enabled by Transfer Printed Single Crystalline Silicon

ABSTRACT Flexible photodetectors that combine high photodetection performance with excellent mechanical compliance are highly desirable for emerging applications such as wearable electronics and conformal optoelectronics; however, their realization remains challenging due to the difficulty in integrating high‐quality semiconductor materials with mechanically flexible device architectures. Here, we report an ultrathin flexible graphene‐silicon (GS) heterojunction photodetector enabled by the transfer of a single crystalline silicon membrane from a silicon‐on‐insulator (SOI) wafer onto a polyimide (PI) substrate. A GS Schottky heterojunction formed between graphene and a 2 µm thick silicon membrane serves as the photosensitive unit, while a redesigned top‐contact electrode configuration ensures compatibility with flexible integration. Encapsulated by flexible substrate and encapsulation layers, the device exhibits an overall thickness below 10 µm. The fabricated flexible photodetector exhibits ultra‐low dark current, stable reverse bias operation, a wide linear dynamic range (LDR) of ∼120 dB under 660 nm, broadband spectral responsivity spanning from the visible to the near infrared region, sub‐microsecond temporal response, and low noise characteristics. This work provides an effective strategy for integrating high‐quality single‐crystalline silicon with graphene to realize ultrathin, high‐performance flexible photodetectors, offering a promising platform for future flexible optoelectronic applications.