Emberion researchers have shown that colloidal quantum dots (QDs) combined with a graphene charge transducer can provide a photoconducting platform with high quantum efficiency and large intrinsic gain, yet compatible with cost-efficient polymer substrates. The team demonstrated methods to couple large QDs (>6 nm in diameter) with organometal halide perovskites, enabling hybrid graphene photo-transistor arrays on plastic foils.
The resulting arrays simultaneously exhibited a specific detectivity of 5 × 1012 Jones and high video-frame-rate performance. PbI2 and CH3NH3I co-mediated ligand exchange in PbS QDs improved surface passivation and facilitated electronic transport, yielding faster charge recovery, whereas PbS QDs embedded into a CH3NH3PbI3 matrix produce spatially separated photocarriers leading to large gain.
The stated that the response time in these devices is limited, and fast switching is only possible by sacrificing the high sensitivity. Furthermore, tuning the QD size toward infrared absorption using conventional organic capping ligands progressively reduces the device performance characteristics.