The project combined thin-film engineering, advanced spectroscopy and microscopy, and LED device prototyping to address two tightly connected questions: (i) how to suppress tin oxidation and harmful defects while keeping beneficial levels of doping, and (ii) how to ensure efficient charge injection and radiative recombination in NIR-LED stacks. The work employed complementary characterization tools (e.g. photoluminescence mapping and quantum-yield analysis, transient spectroscopy to follow carrier dynamics, and structural probes to track crystallization and phase formation) to connect processing conditions with optoelectronic quality.
A key outcome was the demonstration of a molecularly engineered “self-encapsulated” tin-iodide perovskite thin film. By introducing a rationally designed organic molecule into the precursor solution, the film formation was slowed and guided in a way that (a) suppressed rapid degradation in air by mitigating Sn²⁺ oxidation; (b)reduced trap-related losses; and (c) enabled partial control over the p-doping level (without forcing the material to become fully intrinsic).
This self-encapsulation concept delivered clear, measurable improvements. This approach increased the photoluminescence quantum yield, with a reported peak of ~45% under relevant excitation conditions, indicating substantially reduced non-radiative losses. Meanwhile, the perovskite film retained ~60% of its initial photoluminescence after 100 minutes in ambient air (without external encapsulation), whereas reference films degraded immediately. Building on these higher-quality films, the project fabricated NIR-LEDs that achieved a record peak external quantum efficiency (EQE) of 12.4%. Notably, the devices demonstrated measurable functionality in ambient air without external encapsulation (even though long-duration air operation remains a challenge for the broader field).
