Hole transport layer-free photodetector based on perovskite/ZnO quantum dot heterostructure: Enhanced photodetection properties through interface engineering

As a part of this work, organic − inorganic metal halide perovskite (CH₃NH₃PbI₃) films were grown at different annealing temperatures (60, 100, and 140 °C). The findings revealed that the morphological, optical, and structural properties were enhanced by annealing at 60 °C and 100 °C, while increasing the temperature to 140 °C led to the partial decomposition of perovskite into lead iodide (PbI₂). In addition, the self-powered photodetection properties of pristine CH₃NH₃PbI₃ film, and CH₃NH₃PbI₃ grown on ZnO QD-based film and ZnO/Al₂O₃ films were evaluated under illumination with blue (470 nm), green (530 nm), red (660 nm), and white light. The ZnO/CH₃NH₃PbI₃ photodetector (PD) exhibited inferior photoresponse relative to the PD based on pristine CH₃NH₃PbI₃ owing to the CH₃NH₃PbI₃ degradation driven by the basic nature of ZnO QDs. On the other hand, insertion of Al₂O₃ as a passivation layer between ZnO QD-based film and MAPbI₃ suppressed perovskite degradation and enhanced the PD photodetection properties. Upon illumination with blue (470 nm) light, the responsivity, detectivity, and ON/OFF current ratio values of the ZnO/Al₂O₃/CH₃NH₃PbI₃ PD were calculated to be 71.05 mA/W, 5.61 × 10¹² Jones, and 9.3 × 10², respectively. The enhanced photodetection performance was attributed to the effectiveness of the Al₂O₃ passivation layer in reducing the number of trap centers and hydroxyl groups at the ZnO film surface, as evident from XPS results.