MAPbI3 Photovoltaic Cells Efficiency Down to Cryogenic Temperatures

Subodh Mhaisalkar^a, Pablo P. Boix^a, Kunwu Fu^a, Annalisa Bruno^a, Daniele Cortecchia^b, Cesare Soci^c, Xin Yu Chin^c

^aEnergy Research Institute @ NTU (ERI@N), Research Technoplaza, Nanyang Technological University, Singapore, Nanyang Drive, Singapore, Singapore

^bNTU Singapore - Nanyang Technological University, Interdisciplinary Graduate School, Nanyang Avenue, 50, Singapore, Singapore

^cNTU Singapore - Nanyang Technological University, Physics and Appld Physics, Nanyang Avenue, 50, Singapore, Singapore

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)

Swansea, United Kingdom, 2016 June 29th - July 1st

Organizers: James Durrant, Henry Snaith and David Worsley

Oral, Annalisa Bruno, presentation 131
Publication date: 28th March 2016

Methylammonium lead triiodide (MAPbI3) perovskite is an ideal material for photovoltaic applications due to its high light absorption coefficient, ultralong carrier diffusion length (>100 nm)1 and ambiploar semiconducting properties2. However, the current-voltage curves of MAPbI3 solar cells exhibit a strong hysteresis that hinders reliable energy harvesting and stable device operation.3,4 The physical origin of current hysteresis needs to be identified to devise mitigating strategies that will enhance device performance. Three physical processes could be responsible for the observed hysteresis: intrinsic perovskite ferroelectricity, presence of defect states near the perovskite surface acting as traps for charge carriers, and ion motion within the perovskite under bias.5 Here we show that ionic motion is the dominant mechanism underlying hysteresis of MAPbI3 mesoporous solar cells by measuring their performance from room temperature down to 77 K. We observe a reduction of hysteresis at low temperature and its complete disappearance below 170 K, which is consistent with temperature activated diffusion of I- anions (or the motion of the MA+ cations). As the temperature decreases, the solar cell efficiency also decreases due to the reduction of current density. However, application of a 3V pre-bias for 180 s allows recovering the original current density, and to increase device performance up to 20% of its original value at ambient temperature. This enhancement is driven by an increase of the open circuit voltage up to Voc=1.25 V at low temperature. We propose that bias poling is due to ionic motion under applied electric field, which can reduce the electron extraction barrier at the TiO2/MAPbI3 interface.

[1] G. Xing, N. Mathews, S. Sun, S. S. Lim, Y. M. Lam, M. Grätzel, S. Mhaisalkar, T. C. Sum, Science 2013, 342, 344[2] X.Y. Chin, D. Cortecchia, J. Yin, A. Bruno, C. Soci, Nature comm. 2015, 6 , 7383.[3] W. Tress, N. Marinova, T. Moehl, S. M. Zakeeruddin, M. K. Nazeeruddin, M. Gratzel, Energy Environ. Sci. 2015, 8, 995;[4] H. J. Snaith, A. Abate, J. M. Ball, G. E. Eperon, T. Leijtens, N. K. Noel, S. D. Stranks, J. T. W. Wang, K. Wojciechowski, W. Zhang, J. Phys. Chem. Lett. 2014, 5, 1511[5] Yunlong Zou and Russell J. Holmes, Adv. Energy Mater. 2016, 1501994

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