High‐resolution patterning of organohalide lead perovskite pixels for photodetectors using orthogonal photolithography

Organohalide lead perovskite (CH3NH3PbI3) is a novel material with promising applicability for visible light photo-detectors. The ability to develop perovskite photo-detector devices using a low temperature solution based process allows straightforward combinations with other materials, including traditional crystalline semiconductors, with minimal contributions to cost and process complexity. There is, however, a need for high-resolution structuring of the perovskite film to minimize cross-talk between neighboring detectors (pixels) for imaging purposes. This work presents a method to develop Ch3NH3PbI3 thin films possessing high-resolution patterning, using lithography processing with hydrofluoroether solvents. The results presented herein confirm that, unlike the majority of traditional solvents utilized in conventional photolithography, hydrofluoroethers do not adversely affect CH3NH3PbI3 films, enabling photolithographic processing. Transfer of the resist pattern is achieved using a SF6 plasma functionalization process which extracts iodine and organic components from the film, converting the perovskite into PbF2. This work also demonstrates that isolation of perovskite photodetecting pixels with a 20 μm-wide stripe of PbF2 leads to a 4.5-fold reduction in the cross-talk between neighboring pixels. It is believed that our method will facilitate simple monolithic integration of perovskite photodiodes to the silicon backplane chip utilized in active-pixel sensor and charge-coupled device applications.