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Probing longitudinal carrier transport in perovskite thin films via modified transient reflection spectroscopy.

ABSTRACT: Accurate characterization of the longitudinal (along the thickness direction) carrier transport property is of significant importance for evaluating the quality and performance of perovskite thin films. Herein, we report the development of a modified transient reflection (TR) spectroscopy method to realize the direct observation and determination of the longitudinal carrier transport process in MAPbI₃ polycrystalline thin films. Unlike the traditional TR spectroscopy, the carrier transport dynamics along the film thickness is resolved by making the pump (excitation) and probe beams spatially separated on each side of the film, so that the carrier transport from the excitation side to the probe side is directly captured. Utilizing this method, the longitudinal carrier diffusion coefficients (D) in various perovskite films with different thicknesses and grain sizes (extracted from SEM images) are determined, showing D values of ∼1.5 to 1.8 cm² s^-1 (∼0.5 to 0.8 cm² s^-1) for films with grain size larger (smaller) than the thickness. This empirical correlation between the longitudinal D and film thickness/grain size provides a reference for quick quality screening and evaluation of perovskite polycrystalline thin films.

SUBMITTER: Zhao S

PROVIDER: S-EPMC9297385 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Probing longitudinal carrier transport in perovskite thin films <i>via</i> modified transient reflection spectroscopy.

Zhao Shengli S Leng Jing J Wang Shiping S Yan Xianchang X Yin Zixi Z Yin Yanfeng Y Zhang Jun J Jin Shengye S

Chemical science 20220621 28

Accurate characterization of the longitudinal (along the thickness direction) carrier transport property is of significant importance for evaluating the quality and performance of perovskite thin films. Herein, we report the development of a modified transient reflection (TR) spectroscopy method to realize the direct observation and determination of the longitudinal carrier transport process in MAPbI<sub>3</sub> polycrystalline thin films. Unlike the traditional TR spectroscopy, the carrier tran ...[more]

PMID: 35919708

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Project description:The phenomenon of current-voltage hysteresis observed in perovskite-based optoelectronic devices is a critical issue that complicates the accurate assessment of device parameters, thereby impacting performance and applicability. Despite extensive research efforts aimed at deciphering the origins of hysteresis, its underlying causes remain a subject of considerable debate. By employing nanoscale investigations to elucidate the relationship between hysteresis and morphological characteristics, this study offers a detailed exploration of photocurrent-voltage hysteresis at the nanoscale within perovskite optoelectronic devices. Through the meticulous analysis of localized I-V curve arrays, our research identifies two principal hysteresis descriptors, uncovering a predominantly inverted hysteresis pattern in 87% of the locations examined. This pattern is primarily attributed to the energetic barrier encountered at the interface between the probe and the perovskite material. Our findings underscore the pronounced heterogeneity and grain-dependent variability inherent in hysteresis behavior, evidenced by an average Hysteresis Index value of 0.24. The investigation suggests that the localized hysteresis phenomena cannot be exclusively attributed to either photocharge collection processes or organic cation migration at grain boundaries. Instead, it appears significantly influenced by localized surface trap states, which play a pivotal role in modulating electron and hole current dynamics. By identifying the key factors contributing to hysteresis, such as localized surface trap states and their influence on electron and hole current dynamics, our findings pave the way for targeted strategies to mitigate these effects. This includes the development of novel materials and device architectures designed to minimize energy barriers and enhance charge carrier mobility, thereby improving device performance and longevity. This breakthrough in understanding the microscale mechanisms of hysteresis underscores the critical importance of surface/interface defect trap passivation in mitigating hysteretic effects, offering new pathways for enhancing the performance of perovskite solar cells.

Dataset Information

Probing longitudinal carrier transport in perovskite thin films via modified transient reflection spectroscopy.

Publications

Probing longitudinal carrier transport in perovskite thin films <i>via</i> modified transient reflection spectroscopy.

Similar Datasets

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