Inverted Hysteresis in CH3NH3PbI3 Solar Cells: Role of Stoichiometry and Band Alignment

Heping Shen; Daniel A Jacobs; Yiliang Wu; The Duong; Jun Peng; Xiaoming Wen; Xiao Fu; Siva K Karuturi; Thomas P White; Klaus Weber; Kylie R Catchpole

doi:10.1021/acs.jpclett.7b00571

Inverted Hysteresis in CH₃NH₃PbI₃ Solar Cells: Role of Stoichiometry and Band Alignment

J Phys Chem Lett. 2017 Jun 15;8(12):2672-2680. doi: 10.1021/acs.jpclett.7b00571. Epub 2017 Jun 5.

Authors

Affiliations

¹ Research School of Engineering, The Australian National University , Canberra, Australian Capital Territory 2601, Australia.
² Australian Centre for Advanced Photovoltaics, University of New South Wales , Sydney 2052, Australia.
³ Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University , Canberra, Australian Capital Territory 2601, Australia.
⁴ State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University , Guangzhou 510275, China.

PMID: 28557465
DOI: 10.1021/acs.jpclett.7b00571

Abstract

J-V hysteresis in perovskite solar cells is known to be strongly dependent on many factors ranging from the cell structure to the preparation methods. Here we uncover one likely reason for such sensitivity by linking the stoichiometry in pure CH₃NH₃PbI₃ (MAPbI₃) perovskite cells with the character of their hysteresis behavior through the influence of internal band offsets. We present evidence indicating that in some cells the ion accumulation occurring at large forward biases causes a temporary and localized increase in recombination at the MAPbI₃/TiO₂ interface, leading to inverted hysteresis at fast scan rates. Numerical semiconductor models including ion accumulation are used to propose and analyze two possible origins for these localized recombination losses: one based on band bending and the other on an accumulation of ionic charge in the perovskite bulk.