(Invited) Simulations of Ion Diffusion throughout Perovskite Based Solar Cells - Device Level Electrochemistry

Abstract

Defect chemistry plays a major role in the operation of perovskites cells. On one hand they are behind the remarkable self-healing,[1] while on the other they dictate the level of traps, non-radiative recombination,[2] as well as promote ion migration.[3] Moreover, once ions reach the electrodes the device degradation is accelerated.[4, 5] Combining the various reports it seems that if the perovskite would not lose its constituents it would self-heal and if it do lose them it is game-over. We claim that ion migration into the blocking layer is the most important electrochemical process standing in the way of long-term stability. As we will show at the presentation, a significant part of the electrochemistry behind ion leakage and consequently electrode reactions, is captured by a semiconductor device model that accounts for mixed electronic-ionic conduction.[6] While the mere transport of ions introduces no device degradation, introducing oxidation/reduction reactions at the electrodes reproduces the effect of light & bias on device stability. Lastly, we’ll discuss if it is possible to design the device to mitigate this ion leakage out of the perovskite layer. References [1] D. R. Ceratti et al., "Self-Healing Inside APbBr3 Halide Perovskite Crystals," Advanced Materials, vol. 30, no. 10, p. 1706273, 2018, doi: 10.1002/adma.201706273. [2] J. M. Azpiroz, E. Mosconi, J. Bisquert, and F. De Angelis, "Defect migration in methylammonium lead iodide and its role in perovskite solar cell operation," Energy Environ. Sci., 10.1039/C5EE01265A vol. 8, no. 7, pp. 2118-2127, 2015, doi: 10.1039/C5EE01265A. [3] D. Meggiolaro, E. Mosconi, and F. De Angelis, "Formation of Surface Defects Dominates Ion Migration in Lead-Halide Perovskites," ACS Energy Letters, vol. 4, no. 3, pp. 779-785, 2019/03/08 2019, doi: 10.1021/acsenergylett.9b00247. [4] F. Galatopoulos, I. T. Papadas, G. S. Armatas, and S. A. Choulis, "Long Thermal Stability of Inverted Perovskite Photovoltaics Incorporating Fullerene-Based Diffusion Blocking Layer," Advanced Materials Interfaces, vol. 5, no. 20, p. 1800280, 2018/10/01 2018, doi: 10.1002/admi.201800280. [5] B. Rivkin, P. Fassl, Q. Sun, A. D. Taylor, Z. Chen, and Y. Vaynzof, "Effect of Ion Migration-Induced Electrode Degradation on the Operational Stability of Perovskite Solar Cells," ACS Omega, vol. 3, no. 8, pp. 10042-10047, 2018/08/31 2018, doi: 10.1021/acsomega.8b01626. [6] S. Bitton and N. Tessler, "Electronic-ionic coupling in perovskite based solar cells: Implications for device stability," Applied Physics Letters, vol. 117, no. 13, p. 133904, 2020, doi: 10.1063/5.0023902.