Solar Energy Materials & Solar Cells 218 (2020) 110770 Available online 3 September 2020 0927-0248/© 2020 Elsevier B.V. All rights reserved. Study of the effect of temperature on light-induced degradation in methylammonium lead iodine perovskite solar cells Hamid Shahivandi a, ** , Majid Vaezzadeh a , Mohammadreza Saeidi b, * a Department of Solid State Physics, Faculty of Physics, K. N. Toosi University of Technology, Tehran, Iran b Department of Physics, Faculty of Basic Sciences, Shahed University, Tehran, Iran A R T I C L E INFO Keywords: Perovskite solar cell Vacancy Quasi-ions Degradation Born-lande equation ABSTRACT In this paper, the effect of temperature on the process of optical degradation of CH 3 NH 3 PbI 3 perovskite solar cells is studied. First, we promote the theory of the degradation process we have already presented, which leads to more accurate results. Previously, in the proposed model, we had considered the density of the vacancies distributed in the perovskite layer to be constant, while in reality, their density changes over time. In order to obtain the electric feld resulting from the migration of vacancies, which is, in fact, the cause of the optical degradation of the perovskite solar cells, we need the initial density of the vacancies and its temperature dependence as well as migration energy (potential barrier against the migration) of the vacancies. Using the Gibbs free energy resulting from the formation of the vacancies, the density of the vacancies is obtained. Also, by calculating the changes in electrostatic energy between the lattice ions during displacement, the migration en- ergy is obtained. When the required parameters are presented, the temperature dependence of the optical degradation process is discussed using the proposed theory, and the results show the appropriate accuracy of this theory. 1. Introduction Perovskite solar cells as a new generation of high-effciency solar cells have attracted much attention [1–11]. This enormous attention to perovskites and their application in photovoltaic cells are due to the special optical properties of these structures [12,13]. But there are major challenges to the commercialization of perovskite solar cells [2,14], the most important of which is the instability of their performance. This instability is mainly due to defects in the perovskite lattice. Many studies have been performed on improving the stability of perovskite solar cells [15–20]. Improving the operation of the solar cell in the interface of the perovskite layer with other layers of the solar cell [17,18,20], the sub- stitution of the A-site cation with different cations [13,16], and substi- tution of the X-site anion with different anions [15] are some of the ideas that have been done to improve the operation of perovskite solar cells. One of the major problems with the perovskite solar cells is their effectiveness from environmental conditions. Solar cells are always in an uncontrolled outdoor environment, so changes in environmental con- ditions of solar cells are inevitable, and they are always affected by environmental conditions such as temperature, pressure, humidity, etc. Temperature as a variable environmental factor at the solar cell instal- lation site can always affect solar cell performance. Therefore, knowing how temperature affects the solar cell, and trying to control its destructive effects can be important steps in achieving sustainable power conversion effciency. There are two types of charge carriers in the power conversion process for perovskite solar cells. The frst category consists of the electrons and holes through which the power conversion is performed, and the cell life depends on them. The second category consists of ions which can be displaced by the presence of vacancies in the lattice structure. These migrating ions are known to be the major cause of the light-induced degradation of perovskite solar cells [21–25]. Experi- mental evidence indicates that with the onset of exposure, the perovskite solar cell is at its highest power conversion effciency. Over time, the ions move through the vacancies, and the vacancies accumulate on the sides of the perovskite layer. These accumulated vacancies cause a se- vere drop in power conversion effciency. We have already studied the physics of the light-induced degradation process and have provided a suitable model for it [26]. In this model, instead of the migration of ions, we have considered its equivalent, the migration of the vacancies under * Corresponding author. ** Corresponding author. E-mail addresses: h.shahivandi@gmail.com (H. Shahivandi), Saeidi.mr@gmail.com, m.saeidi@shahed.ac.ir (M. Saeidi). Contents lists available at ScienceDirect Solar Energy Materials and Solar Cells journal homepage: http://www.elsevier.com/locate/solmat https://doi.org/10.1016/j.solmat.2020.110770 Received 26 July 2020; Received in revised form 21 August 2020; Accepted 23 August 2020