Differentiated Functions of Potassium Interface Passivation and Doping on Charge-Carrier Dynamics in Perovskite Solar Cells

Abstract

The inclusion of potassium in perovskite solar cells (PSCs) has been widely demonstrated to enhance the power conversion efficiency and eliminate the hysteresis effect. However, the effects of the locations K + cations on the charge-carrier dynamics remain unknown with respect to achieving a more delicate passivation design for perovskite interfaces and bulk films. Herein, we employ the combined electrical and ultrafast dynamics analysis for the perovskite film to distinguish the effects of bulk doping and interfacial passivation of the potassium cation. Transient absorption spectroscopy indicates an enhancement of chargecarrier diffusion for K + -doped PSCs (from 808 to 605 ps), and charge-carrier transfer is significantly promoted by K + interface passivation (from 12.34 to 1.23 ps) compared with that of the pristine sample. Importantly, K + doping can suppress the formation of wide bandgap perovskite phases (e.g., FAPbI 0.6 Br 2.4 and FAPbI 1.05 Br 1.95 ) that generate an energy barrier on the charge-carrier transport channel.

Unraveling Its Intrinsic Role of CH3NH3Cl Doping for Efficient Enhancement of Perovskite Solar Cells from Fine Insight by Ultrafast Charge‐Transfer Dynamics

“…Meanwhile, at the initial period before 1 ps, the broadening of the PB tail indicates the presence of hot carriers. [ 30 ] Meanwhile, the PA signal does not make an obvious appearance, due to its low signal‐to‐noise ratio along with the background color difference. This demonstrates that several different photophysical processes mentioned earlier are interspersed in different time domains.…”

“…This relationship accords with the classical “diffusion‐coupled charge transfer” model, [ 26 ] which is consistent with the previous reports. [ 30 ] The longest τ 4 component with the shape of the bleaching band of perovskite should be assigned to the ground‐state bleach (GSB) recovery process. According to the reports in perovskite/TiO 2 system, [ 38 ] this long‐lived GSB recovery process could result largely from the back‐charge recombination (BCR) from extracted electrons in SnO 2 to the valence band holes of perovskite.…”

“…The mismatched long‐lived CT proved to be the overall apparent diffusion‐included CT, involving not only a rapid interfacial CT process but also a slow charge diffusion from film bulk to interface. [ 26,30 ] Hence, an in‐depth determination of the apparent CT kinetics in PSCs becomes a rewarding and urgent issue.…”

Probing charge carrier dynamics in metal halide perovskite solar cells

“…The process of charge extraction is also characterized by TAS 49,106,112,188–190,191 . The information contained in the spectroscopy obtained through TAS technology is very rich.…”

“…The process of charge extraction is also characterized by TAS. 49,106,112,[188][189][190]191 The information contained in the spectroscopy obtained through TAS technology is very rich. When it is applied to the analysis of the charge extraction process, the required information can be extracted by adjusting the sample structure configuration and the wavelength of the probe light.…”