Electroluminescence, Stark effect and modulation of photophysics in single halide perovskite nanocrystals

Exceptional excitonic properties such as strong absorption and efficient narrow-band emission make lead halide perovskite nanocrystals (NCs) possible candidates to replace semiconductor quantum dots in electroluminescence (EL) devices and other light-emitting and sensing applications. Here, we report a simultaneous study of EL and PL of inorganic halide perovskite nanocrystals of CsPbBr3 on single particle level. We examined the influence of a surrounding matrix on their spectral properties and blinking behavior by dispersing the NCs in an inert matrix of PMMA and in a conductive matrix of PVK/PBD, both on the level of single NCs and aggregates (arrays) of tens of NCs. The differences in the blinking characteristics appear as different parameters of truncated power law distributions of the on-times, both for bright and dim (grey) states. These findings are further corroborated by an effect of externally applied electric field on the blinking dynamics and PL spectra. The applied field enhances the blinking in both matrices, and causes a quadratic Stark shift, the extent of which differs from particle to particle. Based on the above characterization, we fabricated a single-particle light-emitting device by dispersing the NCs at very low concentrations in PVK/PBD matrix as an emitting layer in an ITO/PEDOT:PSS/PVK/PBD/TPBi/LiF/Al device and studied the device by PL and EL single-particle spectroscopy. The same NC can exhibit dramatically different brightness and blinking behavior upon the different modes of excitations, pointing to the origin of the different quantum efficiencies of the PL and EL processes.

Reference

D. K. Sharma, S. Hirata, V. Biju and M. Vacha: Stark effect and environment induced modulation of emission in single halide perovskite nanocrystals. ACS Nano 2019, 13, 624-632