Abstract
<jats:p>Short-wave infrared photodetector stacks based on Lead Sulphide (PbS) promise inexpensive and tunable responsivity in the infrared regime. However, the low charge carrier mobilities of PbS require additional electron (ETL) and hole transport (HTL) layers, which modifies the optical absorption Fabry-Perot profile within the two mirror-like electrodes. This creates a coupled design problem, where changes in transport layer thickness can redistribute optical energy away from the absorber or increase loss in the electrodes and transport layers, thus reducing useful absorption. Here, we introduce a cavity-partitioning perspective for planar PbS photodiode stack, treating the air/ITO/ETL/n-PbS/p-PbS/HTL/Au stack as a coupled lossy Fabry-Perot cavity whereby the electron and hole transport layer thicknesses control the partition of absorption between useful PbS photogeneration and parasitic loss. Subsequently, the HTL behaves as a phase tuning layer that can move the field antinode closer to the hole transport layer, while ETL behaves as a field strength control layer that modulates field amplitude near the electron transport layer.</jats:p>