Photo-Induced Charge Carrier Dynamics of Metal Halide Perovskite

Perovskite solar cells have been recognized as a newly emerging solar cell with the potential of achieving high efficiency with a low cost fabrication process. In particular, facile solution processed cell fabrication facilitated rapid development of optimum cell structure and composition. Over the last few years, the cell efficiency has exceeded 25%.<br/><br/>Highly efficient charge transfer reactions including high charge separation efficiency and swift charge transport are required with minimum charge recombination to achieve the high solar cell performance. Based on previous intensive studies, high efficiency has been achieved by two different film structures: planar heterojunction and mesoporous structures. The latter typically consists of a nanocrystalline TiO₂ film as an electron transport material, lead halide perovskite and <i>spiro</i>-OMeTAD as a hole transport material. Several studies were conducted to understand dynamics of electron and hole injections from the perovskite, their charge carrier transport, and interfacial charge recombination.[1-5] Several parameters have been identified to influence these charge carrier dynamics, and therefore the solar cell performance.[1-5] Clarifying these parameters is extremely important to understand the charge transfer mechanisms to further improve solar cell performance.<br/><br/>In this presentation, we will present parameters controlling charge separation and recombination dynamics at the perovskite interfaces employing a series of transient absorption and emission spectroscopies. Nanosecond transient emission spectroscopy (Vis-ns-TES) clarifies charge separation processes, while Vis-NIR submicrosecond-millisecond transient absorption spectroscopies (NIR-smm-TAS) identify charge separation efficiency and charge recombination rates. Correlation of the dynamics results with the solar cell performance will be discussed [1-5].<br/><br/>This work was partly supported by JSPS KAKENHI Grant (19H02813) and (22H02182), and the Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant number 2021-78 and 2022-99), Japan. We would like to acknowledge supports from the Australia-Japan Foundation for the collaborative project between RMIT University and Kyoto University. We also acknowledge supports from ARC DP fund (DP180103815) and ARC LIEF fund (LE200100051), Australia, and Forefront Research Center, Faculty of Science at Osaka University.<br/><br/><b>References</b><br/>[1] Y. Tachibana, et al. <i>J. Phys. Chem. C</i>, <b>11</b><b>9</b>(35) 20357-20362 (2015).<br/>[2] Y. Tachibana, et al. <i>ACS Appl. Mater. Interfaces</i>, <b>8</b>(22) 13957-13965 (2016).<br/>[3] Y. Tachibana, et al. <i>J. Photopolym. Sci. Technol.</i>, <b>34</b>(3) 271-278 (2021).<br/>[4] Y. Tachibana, et al. <i>Phys. Chem. Chem. Phys.</i>, <b>17</b>(4), 2850 - 2858 (2015).<br/>[5] Y. Tachibana, et al. <i>J. Mater. Chem. C</i>, <b>5</b>, 2182 - 2187 (2017).