Capacitance–voltage characteristics of perovskite light-emitting diodes: Modeling and implementing on the analysis of carrier behaviors

Abstract

Analyzing and optimizing carrier behaviors are essential to achieve high electroluminescence performance in perovskite light-emitting diodes (PeLEDs). In this work, a capacitance–voltage (C–V) model for PeLEDs is established to describe carrier behaviors. Four distinct regions in this typical C–V model, including a neutrality region, a barrier region, a carrier diffusion region, and a carrier recombination region, were analyzed. Importantly, the C–V model is implemented to guide the electroluminescence (EL) performance improvement in PeLEDs. By studying the measured C–V characteristics of a typical PeLED, issues of a high hole injection barrier and insufficient recombination are revealed. To address them, one MoO3 interface layer with deep conduction band minimum is designed between a hole transport layer and a hole injection layer to enhance the hole injection. The C–V characteristics for the optimized PeLED confirm the reduced injection barrier and strengthened recombination rate. The optimized PeLED shows an improved external quantum efficiency from 8.34% to 15.82%. The C–V model helps us to quantitatively understand the essential carrier behaviors in PeLEDs and can serve as an efficient method to improve the EL performance of PeLEDs.

Molecularly Designing a Passivation ETL to Suppress EQE Roll-off of PeLEDs

“…Low-frequency capacitance−voltage (C−V) measurement can effectively reveal the charge injection, trap, and recombination processes. 71 Here, the charge recombination process can be disregarded due to the hole or electron blocking capability in the HOD or EOD, respectively. The J−V and corresponding C−V curves of the EODs are presented in Figure 4c,d.…”

“…The low-frequency capacitance−voltage (C−V) measurements have been proven to be an effective approach to investigate the carrier transport behavior of injected, trapped, and recombined carriers in PeLEDs. This can be expressed by the following equation: 71,73…”

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

“…B) Similar to circuit A but with Z b and Z c detailed.I bc is the total current through the lower branch including radiative and non-radiative processes, see Equation(19), and i rad is the current through the radiative recombination bulk branch, see Equation(26). The part of the circuit corresponding to Z rad , Equation(31), is highlighted with a red dashed rectangle. C) Equivalent circuit used in IS analysis of halide perovskite devices at high applied voltages.…”

“…[30] This methodology will be especially useful when the radiative recombination event is convoluted with previous electronic carrier steps such as transport, trapping, or contact polarization effects, and/or ionic-related phenomena. It has previously been remarked that the capacitance and luminance of LEDs show correlated features [21,31,32] and some studies of electrically stimulated light emission spectroscopy have been reported, [33][34][35] but unfortunately, a general methodology has not been fully developed.Here we describe the first LEVS experiments in halide perovskite LEDs and establish an equivalent circuit model to understand the observed spectra, based on the previous experience in IS. We show that the method provides unique information on the recombination processes that cannot be accessed by purely electrical techniques, thus highlighting the interest of this new experimental technique for the characterization of optoelectronic devices, especially those presenting multiple physical phenomena, as it is the case of halide perovskite-based systems.…”

“…[30] This methodology will be especially useful when the radiative recombination event is convoluted with previous electronic carrier steps such as transport, trapping, or contact polarization effects, and/or ionic-related phenomena. It has previously been remarked that the capacitance and luminance of LEDs show correlated features [21,31,32] and some studies of electrically stimulated light emission spectroscopy have been reported, [33][34][35] but unfortunately, a general methodology has not been fully developed.…”