Revealing the Correlation of Light Soaking Effect with Ion Migration in Perovskite Solar Cells

Abstract

Light soaking (LS) effect of perovskite solar cells (PSCs), i.e., the power conversion efficiency (PCE) increases under continuous light illumination (CLI), has attracted a lot of attention recently. Herein, it is reported that a strong LS effect occurs in the FAxMA1‐xPbI3 (FAMA) PSC for its PCE increases from 7.5% to 20.5% under CLI. Based on the dynamics of the LS effect, drift‐diffusion simulations, and external voltage experiments, it is found that the underlying process for the LS effect is that the generated photovoltage under CLI modulates the distribution of mobile ions in absorber layers increasing charge extraction ability and then alleviating interface recombination, which directly results in the LS effect in FAMA PSCs. In addition, the introduction of Cs+ into perovskite films can reduce the density of accumulated mobile ions at the interface between absorber layers and charge‐transporting layers in FAMA PSCs. As a result, the PCE of the Cs+‐doped device increases from 18.7% to 22.4% under CLI demonstrating that the LS effect in the Cs+‐doped device is suppressed notably. This work reveals the correlation of the LS effect with ion migration and suppresses the LS effect in FAMA PSCs.

Metal Halide Perovskite Surfaces with Mixed A‐Site Cations: Atomic Structure and Device Stability

“…[ 59 − 63 ] Recently, Yu and co‐workers correlated the light‐soaking phenomenon with ion migration. [ 64 ] They attributed the increase in PCE to the photovoltage under continuous light illumination, which leads to the movement of ions within the perovskite film increasing charge extraction. Interestingly, the introduction of Cs + reduced the density of accumulated mobile ions at the interface demonstrating that the light‐soaking phenomenon in the Cs + ‐doped device is suppressed.…”

Photo-processing of perovskites: current research status and challenges

“…Both the PL lifetime and the intensity increase 56,107 . Light from the solar simulator (1 sun) is also effective to induce obvious halide migration and passivate the defects, which boosts the PCE of the perovskite photovoltaic devices 108,109 . Further investigations show that an increase in the built-in electric field can be generated under continuous light irradiation, which leads to an enhancement of the charge extraction ability and eliminates the interface recombination in the perovskite solar cells 109,110 .…”

“…However, the intrinsic mechanism of this light soaking effect is still under debate 112 . Although the light induced thermal effect may also cause lattice expansion, the heating alone cannot lead to enhancement of the PCE 108,109 .…”

“…The light soaking effect can be tuned by controlling the Br/I ratio in the CsPb(Br 1−x I x ) 3 film and the device curing time for inducing maximum efficiency enhancement decreases with an increase in the Br/I ratio 108 . By introducing Cs + in the FA x MA 1-x PbI 3 film, the halide migration can be suppressed and the accumulation of the mobile ions decreases, which gives rise to an increase in the PCE from 18.7% to 22.4% 109 .…”

IonMonger 2.0: software for free, fast and versatile simulation of current, voltage and impedance response of planar perovskite solar cells

“…Lin also simulated the impact of mobile ions on the short-circuit current [46]. (7) Li et al [43] showed how ion migration can explain the lightsoaking phenomenon observed in experiment [65]; and (8) García-Rodríguez et al demonstrated that inverted hysteresis can be explained by the drift-diffusion model, comparing IonMonger simulations to experiment [27].…”