Bulk gamma-InSe has a direct bandgap of 1.24 eV, which corresponds to near infrared (NIR) wavelengths (λ = 1.0 µm) useful in optoelectronic applications from biometric detectors to silicon photonics. However, its potential for optoelectronic applications is largely untapped due in part to the lack of quantitative studies of its optical properties. Here, we study the unusually low absorptance and high photoluminescence quantum efficiency of single-crystalline InSe flakes with thickness in the hundreds of nanometers. InSe emits brightly at room temperature from its direct bandgap with a peak photoluminescence quantum yield (PLQY) of 20 %, despite displaying indirect bandgap like low absorption coefficient due to the symmetry of its crystal structure. By performing pump-dependent PLQY measurements, we extract the radiative and nonradiative recombination coefficients, including the Shockley-Read-Hall and Auger coefficients. Finally, we demonstrate a proof-of-concept alternating current electroluminescent device at low temperature to show the promise of InSe in optoelectronic technology such as highly transparent, bright NIR light sources.
Project is currently funded by: State & Other Govt