Charge-Carrier dynamics of CH3NH3PbI3 Perovskite Films with Different Crystalline Grain Size
Lamiaa Abdelrazik a, Marius Franckevicius a, Vidmantas Gulbinas a
a Center for Physical Sciences and Technology, LT, Savanorių prospektas, 231, Vilnius, Lithuania
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#PhotoPero23 - Photophysics of halide perovskites and related materials – from bulk to nano
València, Spain, 2023 March 6th - 10th
Organizers: Sascha Feldmann, Maksym Kovalenko and Jovana Milic
Poster, Lamiaa Abdelrazik, 316
Publication date: 22nd December 2022

Perovskite-based solar cells (PSCs) have made rapid progress in the past several years. Within a short time, PSCs have emerged a remarkable energy conversion efficiency and the most recent PSCs demonstrate efficiencies of more than 25. [1] This progress was attributed to the improvements in the futures and properties of the used materials such as small exciton binding energy, high absorption coefficient, high charge carrier (CC) mobility, long charge carrier lifetime, and long charge carrier diffusion lengths. However, there are still some fundamental processes that control the operation of the device not totally understood and require more investigation such as the complex behaviors of CC generation, CC relaxation, CC transport, recombination, ion migration, and defect dynamic.

Previous studies discussed the impact of the grain size and grain boundaries on the dynamic of CC, where, the performance and efficiency of solar cells are improved by increasing the crystalline grain size. [2] In this regard, CH3NH3PbI3  (MAPI) perovskite thin films were synthesized by using different concentrations of antisolvent (Chlorobenzene, CB) until achieving the largest grain size that helps in accelerating the extracting of the charge carrier and suppressing the bimolecular recombination.

In this work, we addressed charge carrier motion in perovskite bulk avoiding the influence of interfaces with electrodes. We fabricated perovskite films on comb electrodes with relatively large interelectrode distances of 5 um, and investigated photocurrent dynamics induced by a short laser pulse. In this device configuration, the influence of interfaces on the photocurrent dynamics was negligible in comparison with the carrier motion in perovskite bulk.  We investigated charge carrier motion and extraction for MAPI perovskite with different grain sizes. The photocurrent output is obtained by applying different external voltages and different excitation pulse intensities. To acquire additional information about the decay of carrier density and mobility kinetics, we performed Time-delayed collection field (TDCF) investigations and transient fluorescence decay measurements. We demonstrate that carrier trapping strongly depends on perovskite morphology, while carrier drift rate is additionally reduced by barriers formed by perovskite grain boundaries.

This work was partly financed by European Regional Development Fund under grant agreement No 01.2.2-LMT-K-718-03-0048 with the Research Council of Lithuania.

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