Study of Smooth and Textured Interface in Perovskite Light-Emitting Diodes using Electrochemical Impedance Spectroscopy

R. Kumar
Indian Institute of Technology Roorkee,
India

Keywords: nano structured micro-islands, impedance spectroscopy, perovskite light emitting diodes

Summary:

Owing to the exceptional optoelectronic properties, organic-inorganic halide perovskites (OIHPs) have attracted great attention leading to the variegated application in optoelectronic devices.1 Study of carrier kinetics in perovskite solar cells using Electrochemical Impedance Spectroscopy (EIS) has been the topic of research since the last few years.2 But, research in Perovskite LEDs (PeLEDs) is still sparse. Here, we have fabricated methyl ammonium lead tri-bromide (CH3NH3PbBr3) smooth and textured thin film by spontaneous crystallisation of the perovskite materials. The charge carrier lifetime is enhanced in textured morphology along with the photoluminescence intensity. This can be attributed to the smaller crystal size in nano-structured micro-islands on the top of smooth background in textured film. We have studied the charge carrier kinetics of smooth and textured interface in PeLEDs using EIS at different applied bias. The electrical equivalent circuit of the device was modelled, and the variation of different parameters with applied bias was studied. We have observed anomalous capacitive behaviour for the first time at mid-frequency regime due to the interplay between electronic and ionic charge transport. In addition, this device capacitance significantly depends on the morphology of the perovskite emissive layer. We have proposed a possible model responsible for this anomalous capacitive behaviour and its correlation with perovskite emissive layer morphology in PeLEDs. References 1. Lin, K. et al. Nat. 562.7726, 245 (2018) 2. Bag, M. et al. J. Am. Chem. Soc. 137, 13130-13137 (2015)