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( Ganesh Ghimire ),( Yongjun Lee ),( Seokjoon Yun ),서창원,( Hyun Kim ),( Roy Aad ),( Young Hee Lee ),김정용 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Monolayer transition metal dichalcogenide (1L-TMDs) provides a convenient platform to design light emission from 2 dimensionally confined excitonic systems. Many body effects arising from strong interactions among carriers have been of considerable interest in nanoscience. The exciton-exciton annihilation (EEA) process reduces the generated excitons density and affects the performances of the opto-electronic devices. We studied multiexciton dynamics in chemically treated TMDs like MoS<sub>2</sub>, WS<sub>2</sub> and WSe<sub>2</sub> using non-linear photoluminescence (PL) spectroscopy. We also studied the many body correlations between excitons in pristine and chemically treated 1L-TMDs by excitation power dependence of PL and time resolved PL spectroscopy. We observed the decrease of the EEA rate after the chemical treatment.
Moyen, Eric,Kanwat, Anil,Cho, Sinyoung,Jun, Haeyeon,Aad, Roy,Jang, Jin The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.18
<P>Perovskite quantum dots have recently emerged as a promising light source for optoelectronic applications. However, integrating them into devices while preserving their outstanding optical properties remains challenging. Due to their ionic nature, perovskite quantum dots are extremely sensitive and degrade on applying the simplest processes. To maintain their colloidal stability, they are surrounded by organic ligands; these prevent efficient charge carrier injection in devices and have to be removed. Here we report on a simple method, where a moderate thermal process followed by exposure to UV in air can efficiently remove ligands and increase the photo-luminescence of the room temperature synthesized perovskite quantum dot thin films. Annealing is accompanied by a red shift of the emission wavelength, usually attributed to the coalescence and irreversible degradation of the quantum dots. We show that it is actually related to the relaxation of the quantum dots upon the ligand removal, without the creation of non-radiative recombining defects. The quantum dot surface, as devoid of ligands, is subsequently photo-oxidized and smoothened upon exposure to UV in air, which drastically enhances their photo-luminescence. This adequate combination of treatments improves by more than an order of magnitude the performances of perovskite quantum dot light emitting diodes.</P>