Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 12, Issue 30, Pages 34265-34273Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c04489
Keywords
perovskites light emitting diode; electrochemical impedance spectroscopy; negative capacitance; ideality factor; morphology
Funding
- Science and Engineering Research Board, Department of Science and Technology, INDIA [ECR/2016/001530]
- National Center for Photovoltaic Research and education (NCPRE), IIT Bombay
- Ministry of Human Resource Development (MHRD)
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Perovskite light-emitting diodes have almost reached the threshold for potential commercialization within a few years of research. However, there are still some unsolved puzzles such as large ideality factor and the presence of large negative capacitance especially at the low-frequency regime yet to be addressed. Here, we have fabricated a methylammonium lead tri-bromide perovskite n-i-p structure for light-emitting diodes from a smooth and textured emissive layer and demonstrated for the first time that these two factors are strongly dependent on the perovskite film morphology. Bias-dependent capacitance measurement also reveals the transition between negative to positive capacitance in textured films at the low-frequency regime. We have observed an anomalous capacitive behavior at the mid-frequency regime in smooth perovskite films but not in textured films. The relatively large ideality factor and anomalous capacitive behavior observed in perovskite light-emitting diodes are due to the presence of strong coupling between ions and electrons near the electrode interface. Therefore, the ideality factor and anomalous capacitance at the mid-frequency regime can be decreased by minimizing electronic-ionic coupling in textured perovskite films, while light outcoupling can be improved significantly.
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