Improved Operation Stability of Colloidal Quantum Dots Photodiodes via Suppressing Ion Migration

Solution-processed colloidal quantum dots (CQDs) photodiodes are compatible for monolithic integration with silicon-based readout circuit, enabling high-performance and low-cost infrared imaging. However, operation stability of CQDs photodiodes has rarely been explored, which is one of the main obstacles for CQDs imaging commercialization. Here, we reveal that the performance deterioration of the CQDs photodiodes under strong electric field at high temperature is mainly attributed to ion migration in CQDs film, clearly clarified by aging photoconductors based on each functional layer of CQDs photodiodes. The halide ion migration through vacancy increases the defect density of the CQDs layer and blocks device interfaces, resulting in increased dark current density and postponed saturation voltage. We introduce polyimide (PI) into CQDs film to efficiently block the pathway for halide ion migration. As a result, the CQDs photodiodes with PI achieve greatly improved operation stability over 27 h under 104 V/cm electric field at 85 °C.