Origin of Broadband Emission in Low Dimensional Halide Perovskites

In this talk, I will provide an overview on research activities of our research group with emphasis on electroluminescent devices. Majority of this work is focused on molecular semiconductor and halide perovskites. In this talk I would show results of single junction OLEDs, single color tandem OLEDs and color tuneable vertically stacked tandem OLEDs. Further, triplet excitons are key aspects to enhance the efficiency and hence understanding triplet excitons is key for the success of these devices. Which will be further extended to halide perovskites too.<br/>Here in this talk, we will discuss the origin of broadband illumination and other emission peaks using temperature-dependent time-resolved photoluminescence (PL) spectra of 2D layered halide perovskites semiconductors. For temperatures below 100 K, (PEA)₂PbBr₄film gives broad PL emission, stoke shifted by 750 meV from narrow exciton emission peaks, whereas (PEA)₂PbI₄film does not show any broad emission. Kinetics of various peaks could provide useful insight to propose a consistent energy level scheme associated with a barrier (PEA) and well (PbX₆^4-) material system’s electronic states. This broad emission in (PEA)₂PbBr₄perovskite is observed due to coupling of electronic states in inorganic well part and organic barrier part, which is in contrast to a proposed model based on self-trapped-exciton.<br/><br/><b>Reference: </b><br/>G Banappanavar, S Vaidya, U Bothra, LR Hegde, KP Sharma, RH Friend and D. Kabra (2021) “Novel optoelectronic technique for direct tracking of ultrafast triplet excitons in polymeric semiconductor” <i>Appl. Phys. Rev. </i>Vol. 8, p-031415 (2021)<br/><br/>Laxmi and D. Kabra “Origin of Contrasting Emission Spectrum of Bromide vs Iodide Layered Perovskite Semiconductors” <i>J. Phys. Chem. Lett.</i> Vol. 13, p-2737 (2022)