We report a five-fold luminance increase of green-light-emitting CdSe@ZnS quantum-dot LEDs (QLEDs) in response to treatment with a 2-ethoxyethanol solution of cesium carbonate (Cs2CO3). The maximum luminous yield of Cs2CO3-treated QLED is as high as 3.41 cd A-1 at 6.4 V. To elucidate device-performance improvement, we model measured currents as the sum of radiative and non-radiative recombination components, which are respectively represented by modified Shockley equations. Variations in model parameters show that a shift in Fermi level, reduction of barrier heights, and passivation of mid-gap defect states are the main results of Cs2CO3 treatment. In spite of a large luminance difference, light-extraction efficiency remains the same at 9% regardless of Cs2CO3 treatment because of the similarity in optical structures.
This work was partly supported by the \u2018Human Resources Program in Energy Technology\u2019 of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy (MOTIE), Republic of Korea (No. 20164030201380), and partly by the GRRC program of Gyeonggi province [GRRC-AJOU2016B03, Photonics-Medical Convergence Technology Research Center]. HTN acknowledges financial support from the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.03-2020.09.
