The Charge Transport/Recombination Dynamics in Planar Perovskite Solar Cells
Xi-Cheng Ai a, Jian-Ping Zhang a, Yujun Qin a, Hao-Yi Wang a, Yi Wang a, Man Yu a
a Department of Chemistry Renmin University of China, No. 59,ZhongGuanCun Street, Haidian District, Beijing 100872, Beijing, 100872, China
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
Oral, Man Yu, presentation 102
Publication date: 7th November 2016

In the past few years, we have all witnessed the unprecedented zeal for the rapid growth of the organometal halide perovskite solar cell field. The tremendous efforts devoted to device fabrication and optimization have led to PCEs exceeding 20%. In spite of such an impressive development, an in-depth understanding of many of the physical properties of this class of eclectic materials remain elusive, including the energetic distribution of trap states, the dynamics of charge transport/recombination and light harvesting efficiency in the assembled planar solar cells. The underlying mechanism of the carrier transport/recombination processes are systematically studied by optoelectronic transient measurements. The transient photocurrent (TPC) and photovoltage (TPV)measurements are frequently used to elucidate the mechanism of photoelectrical conversion processes and evaluate charge transport/recombination lifetime in the planar perovskite solar cells. The photovoltaic performance of planar perovskite solar cell is significantly influenced by the morphology of perovskite film. We found that best morphology of perovskite film prepared from the moderate concentration of CH3NH3Cl in precursor solutions results the excellent photovoltaic performance with an average efficiency of 15.52% and a champion efficiency of 16.38%. The results of transient optoelectronic measurements, TPV and TPC, indicate that the morphology of perovskite film strongly influences the charge recombination and transport processes in planar perovskite solar cells, as proved by the derived charge collection efficiency. The cell with the best perovskite film exhibits slowest recombination and fastest transport dynamics. In addition, it is found that improper CH3NH3Cl may bring about more trap states. Density-of-state distribution is investigated by means of time-resolved charge extraction (TRCE). For TRCE measurements, photogenerated electrons under a given photovoltage are dumped out at specified timing by rapidly switching the solar cells from open- to short-circuit conditions. In a word, the preparation of high-quality perovskite film with controllable morphologies via chloride to optimize charge recombination and charge transport is significant for fabricating high-performance perovskite solar cells.

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