Perovskite solar cells are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective energy production. In only several years, an unprecedented progression of preparation procedures and material compositions delivered a prototype technology that exploits most of the potential for perovskites as photovoltaic materials. However, there remains a vast scope to demonstrate that perovskite solar cells are stable under working conditions
Migration of ions within the perovskite crystal lattice has been widely investigated to explain the “hysteresis” of current-voltage (J-V) characteristic of perovskite solar cells. The results of these studies indicated that, regardless of the particular device architecture and materials composition, halides (and their vacancies) migrate within the perovskite layer and accumulate at the interface with selective charge contacts. Depending on particular voltage and light bias conditioning, accumulation of ions (and their vacancies) reduces the charge collection efficiency. This mechanism has been suggested as the most likely cause of J-V “hysteresis”, but it may also have a significant impact on the long-term stability of devices under working conditions. Understanding the effect of ion migration on device long-term performance is of paramount importance because it will answer the question whether or not there is an intrinsic instability that may ultimately prevent from using perovskites for photovoltaics.
In this talk, I will demonstrate ion migration in perovskite solar cells working under different voltage bias conditions and I will discuss the impact of ion migration on the initial device power conversion efficiency and long-term stability. Thus, I will demonstrate perovskite solar cells stabilised for several hundred hours close to the initial efficiency.