Light Intensity Dependence Study of Mixed-composition Perovskite Solar Cells
Richard Murdey a, Minh Anh Truong a, Kento Otsuka a, Ruito Hashimoto a, Tomoya Nakamura a, Atsushi Wakamiya a
a Kyoto University, Japan, Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP20)
Tsukuba-shi, Japan, 2020 January 20th - 22nd
Organizers: Michio Kondo and Takurou Murakami
Oral, Richard Murdey, presentation 095
Publication date: 14th October 2019

  Metal-halide perovskites are exciting materials for solar cell applications due to their high photogeneration efficiencies and ease of fabrication.  The stability of perovskite solar cells, however, is poor – particularly under full sunlight and harsh outdoor conditions.  Ambient light energy harvesting in indoor environments, where stability concerns are less acute, is therefore an attractive near term application for emerging perovskite technologies.  Not all solar cells operate efficiently in low light, however, so in this study we set out to examine the properties and performance of our highly efficient mixed-composition Cs0.05FA0.80MA0.15PbI2.75Br0.25 perovskite devices1 as a function of light intensity.

  A typical cell was found to retain about 25% of the maximum efficiency down to the lowest measured light intensities of 0.03 mW/cm2 (1/3000th of full sunlight, or 30 Lux).  The maximum efficiency is observed at 10 mW/cm2 (1/10th of full sunlight, 10 000 Lux).  In addition to current-voltage analysis, impedance spectroscopy was employed to investigate the underlying mechanisms governing the change in cell performance.  The parallel resistance, r­­p, resolved by the impedance measurements, is compiled as a function of applied bias voltage and incident light intensity.   While usefully high at ambient light levels, the parallel resistance falls dramatically in stronger light, particularly at moderate voltages, resulting in significant loss of fill factor.  The FF loss is shown to be the primary cause of the reduction in cell efficiency above 10 mW/cm2.  These results can be comprehensively explained by introducing a field-dependent photocurrent into the standard equivalent circuit, and is accurately modelled using the constant-field approximation developed previously for amorphous Si photodiodes.2,3

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