Mapping charge carrier distributions and energy loss in perovskite devices

The success of semiconductors in various optoelectronic devices can largely be attributed to the fine control of local charge carrier populations. Charge carrier distributions throughout a device stack are controlled by several sources including charge traps, band bending, and phonons. Uncovering a clear picture of charge carrier behavior upon photoexcitation has been an ongoing challenge that often requires using a complementary set of optical and electrical probes. Here, I discuss the tuning of local surface fields in 3D/2D perovskite heterostructures to controllably move charge carriers as well as new multimodal optical probes that can rapidly identify sources of energy loss throughout a device. With careful control of surface fields, we are able to reduce the surface recombination velocity at a perovskite/charge transport layer from 3500 cm/s to 7 cm/s, one of the lowest values measured to date. These results identify new processing methods and measurement tools to control local charge carrier populations and distributions, which are a critical toolset in optimizing perovskite devices.