Characterization of Planar Lead Halide Perovskite Solar Cells by EIS, OCPVD and IMVS/IMPS

Petra J. Cameron^a, Adam Pockett^a, Laurence M. Peter^a, Henry J. Snaith^b, Giles E. Eperon^b, Timo Peltola^c, Alison Walker^c

^aDepartment of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom

^bUniversity of Bath, Department of Physics, Claverton Down, Bath BA2 7AY, United Kingdom

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Adam Pockett, 409
Publication date: 5th February 2015

Despite a rapid rise in device record efficiencies, the level of understanding of the operation of perovskite solar cells is still some way behind. It is undoubtedly a promising material for the next-generation of commercially viable solar power generation, but for development to continue a number of issues need to be overcome. A better understanding of carrier transport and recombination processes will enable device architecture to be tuned for optimum performance, and may also give insights into other potential materials with similar properties. In this work, a range of complimentary characterisation techniques have been employed to study planar heterojunction mixed-halide precursor derived devices¹. These techniques include electrochemical impedance spectroscopy, intensity modulated photovoltage/photocurrent spectroscopy and open-circuit photovoltage decay measurements. Distinct variations in performance at low light intensities were observed for supposedly identical cells (see figure), possibly due to subtle differences in the crystallisation process. The non-ideality factors for these cells varied between groups around m≈2.5 and m≈5. It was also found that the geometric capacitance of the absorber layer dominates the total cell capacitance, as opposed to charge accumulation due to photogenerated carriers (chemical capacitance). Good consistency was observed between techniques, including agreement between small and large amplitude perturbation techniques. The cells with m≈2.5 showed a persistent photovoltage decay that was absent in the case of the cells with higher ideality factors. Recombination losses at short-circuit were also observed in the IMPS response.

Intensity dependence of the open-circuit voltage for two different cells, showing a distinct difference in the cell non-ideality.
A. Pockett, G. E. Eperon, T. Peltola, H. J. Snaith, A. Walker, L. M. Peter and P. J. Cameron, J. Phys. Chem. C, 2015, Accepted.

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