High-Detectivity/-Speed Flexible and Self-Powered Graphene Quantum Dots/Perovskite Photodiodes

For high-performance organic-inorganic halide perovskite photodiodes (PDs), good quality of the active and charge-transport layers is highly required because the former is the primary source of photogenerated electron-hole pairs and the interface between the layers has a strong influence on the recombination of the carriers. Here, we first report perovskite PDs employing graphene quantum dots (GQDs)-mixed MAPbI₃/hole-transport layer (HTL) and doped-graphene transparent conductive electrode. By adding the GQDs to the perovskite layer and HTL, the crystallinity of the perovskite layer is enhanced and the work function of HTL is increased, leading to efficient generation of carriers in the active layer and reduced recombination at the active layer/HTL interface. The resulting best detectivity and response time are 8.7 × 10¹²/8.42 × 10¹² cm Hz^1/2 W^-1 and 0.96/0.96 μs for rigid/flexible PDs, respectively, at 0 V bias, meaning "self-powered", comparable to or even better than those of previously reported perovskite PDs. The flexible PDs also show excellent stability by maintaining 80% of the initial responsivity even after repeated bending for 1000 cycles at a bending radius of 4 mm. These results suggest that the addition of GQDs is very useful for enhancing the photosensing capability and flexibility of the perovskite PDs.