Biphasic Charge Carrier Recombination Mechanism in Mesoporous Perovskite Solar Cells
Jian-Ping Zhang a, Xi-Cheng Ai a, Yujun Qin a, Pu Zhang a, Zhi-Xin Guo a, Man Yu a, Jun Han a, Hao-Yi Wang a, Yi Wang b
a Department of Chemistry, Renmin University of China, No. 51 Zhongguancun Avenue, Beijing, 100872, China
b Department of Chemistry, National University of Singapore, 21 Lower Kent Ridge Road, Singapore, 119077, Singapore
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Poster, Hao-Yi Wang, 110
Publication date: 7th November 2016

Organic-inorganic perovskite solar cells containing various device structures (mesoporous, planar and inverted structured), which origin from conventional dye sensitized solar cells (DSSCs), have surged great waves in photovoltaic field owing to their peculiar advantages. However, comparing with the relatively mature development of charge carrier recombination research in DSSCs, the related studies are still on the initial stage in perovskite solar cells. The most accepted charge carrier recombination mechanism of trap-limited charge carrier recombination in DSSCs is not suitable for perovskite solar cells, especially the mesoporous structured perovskite solar cells, which has the most similar device structure with DSSCs. In our work, conventional DSSCs and mesoporous structured perovskite solar cells were prepared and their charge carrier recombination properties were measured and investigated by transient photovoltage decay method. In DSSCs the charge carrier recombination process is predominated by the trap states in mesoporous TiO2 phase, and thus, leading to a mono-exponential recombination decay process. However, in mesoporous structured perovskite solar cells, we found that the perovskite phase also plays a crucial role in charge carrier recombination process, i.e., at low Fermi level, photo-generated electrons predominately populate in perovskite phase, while at high Fermi level, most electrons occupy traps in mesoporous TiO2. As a result, the dynamics of charge carrier recombination is respectively dominated by perovskite phase and mesoporous TiO2 in these two cases.1 Further investigation suggests that the demarcation voltage between perovskite-dominated and TiO2-dominated recombination process is influenced by the trap state distribution & density of perovskite.2 Recently, a physical model based on multiple trap theory is proposed by taking into account both the contributions of perovskite phase and mesoporous TiO2 phase, which is suitable to describe the biphasic charge carrier recombination process in mesoporous structured perovskite solar cells.3 These findings provide a novel horizon for the understanding of the charge carrier recombination process in perovskite solar cells.  

1. H. Y. Wang, Y. Wang, M. Yu, J. Han, Z. X. Guo, X. C. Ai, J. P. Zhang and Y. Qin, Phys. Chem. Chem. Phys., 2016, 18, 12128-12134.

2. H. Y. Wang, M. Y. Hao, J. Han, M. Yu, Z. X. Guo, P. Zhang, Y. Qin, X. C. Ai, J. P. Zhang, Under review.

3. H. Y. Wang, Y. Wang, M. Y. Hao, J. Han, M. Yu, Z. X. Guo, P. Zhang, Y. Qin, X. C. Ai, J. P. Zhang, In preparation.

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