Flexible and Self-Supporting Si-Based Photodetector with Fast Response Speed for Visible Light Communication

Si-based photodetectors (PDs), commonly used as optical receivers in visible light communication (VLC) systems, generally lack flexibility and face a dilemma between responsivity-response speed. This study reports a flexible Si/SnO2 heterojunction by conformally coating a SnO2 thin film on the self-supporting, pyramid-shaped Si film to efficiently absorb visible light and rapidly extract photogenerated carriers, thereby breaking the responsivity-response speed dilemma. The as-prepared PD under blue light achieves a responsivity of 0.267 A/W and a rise (decay) time of 3.1 μs (4.1 μs), which is shorter than that of most previously reported flexible Si-based PDs. The flexible device further presents excellent stability and adaptability to curved surfaces. In the bending state with a curvature radius (ρ) of 1 cm, the optical reception angle expands by 24° compared to that of the planar state. Under the condition of meeting the forward error correction threshold, the bending PD with ρ = −1 cm for character transmission can deviate from the illumination center at a maximum distance 2.1 times larger than that in the planar case. This work proposes a new flexible PD and its application scheme for Internet of things (IoT) and VLC applications.