Influence of Ligands on the Optical Properties of CsPb(BrI)3 NC Films
Andreas Manoli a, Paris Papagiorgis a, Maryna Bodnarchuk b c, Yuliia Berezovska b c, Maksym Kovalenko b c, Grigorios Itskos a
a Experimental Condensed Matter Physics Laboratory, Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus
b Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
c Laboratory for Thin Films and Photovoltaics, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
Proceedings of International Conference on Emerging Light Emitting Materials (EMLEM22)
Materials for next generation LEDs and lasers:
Limasol, Cyprus, 2022 October 3rd - 5th
Organizers: Maksym Kovalenko, Maryna Bodnarchuk and Grigorios Itskos
Poster, Andreas Manoli, 080
Publication date: 15th July 2022

Lead halide perovskite nanocrystals (LHPs NCs) exhibit outstanding spontaneous and stimulated emission properties that include high photoluminescence quantum yield (PL QY), narrow emission linewidth, short radiative lifetime and high optical gain. Over the past few years, various studies showed that the structural integrity and optoelectronic properties of LHP NCs can be further improved by the development of new surface chemistry and the addition of new ligand complexes.  

Herein, a comprehensive spectroscopic study is presented to probe the impact of two novel passivation strategies based on didodecyldimethylammonium bromide (DDAB) and oleylguanidinium bromide (OGB) ligands on the photophysical properties of red-emitting CsPb(BrI)3 NCs. Compared to NCs capped with conventional oleic acid/oleylamine (OA/ Om) complexes, the new ligands are found to increase the PL QY of the NCs in the solid state by up to 4 times and the average exciton PL lifetime by up to 6 times. Temperature-dependent PL studies provide evidence of reduced surface trap depth and increased exciton binding energy in the NCs passivated by the DDAB and OGB ligands, further confirming the improved surface passivation. The suitability of the new ligands for photonic applications is finally demonstrated by the employment of the DDAB- CsPb(BrI)3 NCs as active gain media in solution-processed cavities formed by polymeric distributed bragg reflectors (DBRs), allowing activation of amplified spontaneous emission using quasi-cw, microsecond lasing excitation with an energy density threshold of 565 μJ/cm2.

This work was financially supported by the Research and Innovation Foundation of Cyprus, under the "NEW STRATEGIC INFRASTRUCTURE UNITS-YOUNG SCIENTISTS" Program.

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