Unveiling the Morphology Effect on the Negative Capacitance and Large Ideality Factor in Perovskite Light-Emitting Diodes

Abstract

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.

Influence of Halide Substitution and External Stimuli on Ion Transport in Inverted MAPb(I1-xBrx)3 Perovskite Solar Cells

“…The capacitive response of PSC can be divided into three distinct frequency regimes namely, low (f < 100 Hz), intermediate (100 Hz < f < 0.1 MHz), and high (f > 0.1 MHz). 20 The high and intermediate frequency is often related to the chemical capacitance and dipole contributions, 21 respectively, whereas the low frequency response represents the electrode polarization due to the accumulation of charges 22 and ion migration. 23 As shown in Figure 1, the high frequency capacitance does not change with light intensity hence, it can be treated as a geometric capacitance.…”

Interface engineering improves the performance of green perovskite light-emitting diodes

“…2f portrays the Nyquist plot of the PeLEDs measured under an applied bias of 4 V, revealing that the PeLEDs addressed with AT possess a smaller radius than that of the pristine device, which further indicates the reduced charge transfer resistance due to ATinduced interface engineering. 6,31 To further estimate the relationship between the device performance and interface modification, space-charge-limited-current (SCLC) measurements were performed to explore the defect density. 15,[32][33][34] The current density-voltage ( J-V) curves of the hole-only devices with an architecture of ITO/pure or AT-modified PEDOT:PSS/perovskite/molybdenum oxide (MoOx)/silver (Ag) are depicted in Fig.…”

Advanced Strategies to Tailor the Nucleation and Crystal Growth in Hybrid Halide Perovskite Thin Films

“…Good perovskite film morphology does not always refer to a smooth, pinhole-free, and compact perovskite film but is also expected to have favorable interfacial electrical properties. Using the antisolvent treatment and controlling the dripping delay, Kumar et al demonstrated that film morphology can be tuned by tuning the route of the crystal growth, and thus, both the smooth and the textured perovskite film can be designed accordingly ( Kumar R. et al, 2020 ). These textured films show better charge injection/extraction properties at the perovskite/electron transport layer interface in the perovskite light-emitting diode as compared to the archetypical smooth films.…”