In Situ Ultrafast Charge Carrier Dynamics of the Two-Dimensional Perovskites

Skyrocketing the power conversion efficiency (PCE) of organic-inorganic metal halide perovskite (HOIP) beyond 25%, makes it a promising candidate for the low-cost next generation thin film based solar cell technology. However, long term environmental stability hinders its further development in their commercial application. Interestingly, Two-dimensional (2D) perovskite, originating from 3D perovskite structures, can be tuned by atomic scales, leading to electronic band structure tunability beyond 3D perovskites. In addition, they show much higher environmental stability as compared to their 3D counterpart. However, the carrier photogeneration and transport mechanisms remain unclear.<br/>In comparison to that widely explored time-resolved optical spectroscopic techniques including pump–probe and fluorescence approaches to investigate carrier diffusion dynamics, we have used the novel ultrafast photocurrent spectroscopy to investigate the carrier drift dynamics.[i]^,[ii] In this project, we have investigated the 2D perovskites system including type 1 and type 2 perovskite (e.g., (4Tm)₂SnI₄, (4Tm)₂PbI₄, (BTm)₂PbI₄, BA₂PbI₄) and elucidated the nature of fundamental carrier photogeneration mechanism. Inaddition, to the proposed free carrier generation model, we demonstrated the importance of interlayer spacing in determining the exciton binding energy. Our work establishes the foundation for the 2D perovskite application in photovoltaics, photodetection, and LEDs.<br/><br/><b>Keywords:</b> low dimensional, drift dynamics, charge trapping, exciton diffusion<br/><br/><br/>[i]Kobbekaduwa, K.; Liu, E.; Zhao, Q.; Bains, J. S.; Zhang, J.; Shi,Y.; Zheng, H.; Li, D.; Cai, T.; Chen, O.; Rao, A. M.; Beard, M.C.; Luther, J.M.; and Gao, J. Ultrafast Carrier Drift Transport Dynamics in CsPbI₃ Perovskite Nanocrystalline Thin Films. <i>ACS Nano</i><b> 2023</b>, 17, 13997–14004.<br/><br/><br/>[ii]Kobbekaduwa, K. et al. In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions. <i>Nat. Commun.</i> <b>2021</b>, <i>12</i>, 1636.