期刊
MATERIALS ADVANCES
卷 2, 期 20, 页码 6613-6619出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/d1ma00650a
关键词
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资金
- Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN) [320165]
- Academy of Finland [326455]
- Finnish Cultural Foundation [00210670]
- Business Finland
- Forschungszentrum Julich GmbH (SolarWAVE project)
- Jane & Aatos Erkko foundation (project ASPIRE)
- Tampere University
- Academy of Finland (AKA) [326455, 326455] Funding Source: Academy of Finland (AKA)
This study comprehensively investigated the charge carrier diffusion in CsMAFA perovskite and found evidence of non-ambipolar diffusion. The migration of electrons without being hindered by holes challenges the common assumption of ambipolar diffusion in these materials. Additionally, the diffusion deceleration due to traps and grain boundaries after a certain period questions the reported ultrafast diffusion and provides an alternative explanation for the slow cooling observed in perovskites.
We performed a comprehensive study of the charge carrier diffusion in the CsMAFA perovskite, one of the state-of-the-art perovskites for photovoltaic applications, starting from the diffusion of hot carriers to the eventual trapping at the surfaces and grain boundaries. We discovered evidence of non-ambipolar diffusion by using ultrafast transient reflectance spectroscopy: by comparing the transient reflectance signals of perovskite samples to a GaAs reference sample, we saw that the electrons diffused at their maximum mobility without being hindered by the slower holes. These findings dispute the common assumption of ambipolar diffusion in these materials. Then, after a few tens of picoseconds, the diffusion decelerated from 1.6 cm(2) s(-1) to 0.2 cm(2) s(-1) due to traps and grain boundaries. The hot-carrier dynamics of perovskites have also garnered great interest thanks to their reported quasi-ballistic mobility and the slow cooling caused by the hot-phonon bottleneck. However, our findings dispute the ultrafast diffusion and provide an alternative explanation for the prolonged cooling. Based on our analysis, we recommend paying great attention to the carrier distribution when conducting hot-carrier studies.
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