Broad-Band Photodetectors Based on Copper Indium Diselenide Quantum Dots in a Methylammonium Lead Iodide Perovskite...

Low-temperature solution-processed methylammonium lead iodide (MAPbI₃) crystalline films have shown outstanding performance in optoelectronic devices. However, their high dark current and high noise equivalent power prevent their application in broad-band photodetectors. Here, we applied a facile solution-based antisolvent strategy to fabricate a hybrid structure of CuInSe₂ quantum dots (CISe QDs) embedded into a MAPbI₃ matrix, which not only enhances the photodetector responsivity, showing a large on/off ratio of 10⁴ at 2 V bias compared with the bare perovskite films, but also significantly (for over 7 days) improves the device stability, with hydrophobic ligands on the CuInSe₂ QDs acting as a barrier against the uptake of environmental moisture. MAPbI₃/CISe QD-based lateral photodetectors exhibit high responsivities of >0.5 A/W and 10.4 mA/W in the visible and near-infrared regions, respectively, partly because of the formation of a type II interface between the respective semiconductors but most significantly because of the efficient trap-state passivation of the perovskite grain surfaces, and the reduction in the twinning-induced trap density, which stems from both CISe QDs and their organic ligands. A large specific detectivity of 2.2 × 10¹² Jones at 525 nm illumination (1 μW/cm²), a fast fall time of 236 μs, and an extremely low noise equivalent power of 45 fW/Hz^1/2 have been achieved.