Crystal Reorientation and Amorphization Induced by Stressing Efficient and Stable P–I–N Vacuum‐Processed MAPbI<sub>3</sub> Perovskite Solar Cells
İsmail Cihan Kaya, Kassio P. S. Zanoni, Francisco Palazón, Michele Sessolo, Hasan Akyıldız, Savaş Sönmezoğlu, Henk J. Bolink
Abstract
Herein, the long‐term stability of vacuum‐deposited methylammonium lead iodide (MAPbI 3 ) perovskite solar cells (PSCs) with power conversion efficiencies (PCEs) of around 19% is evaluated. A low‐temperature atomic layer deposition (ALD) Al 2 O 3 coating is developed and used to protect the MAPbI 3 layers and the solar cells from environmental agents. The ALD encapsulation enables the MAPbI 3 to be exposed to temperatures as high as 150 °C for several hours without change in color. It also improves the thermal stability of the solar cells, which maintain 80% of the initial PCEs after aging for ≈40 and 37 days at 65 and 85 °C, respectively. However, room‐temperature operation of the solar cells under 1 sun illumination leads to a loss of 20% of their initial PCE in 230 h. Due to the very thin ALD Al 2 O 3 encapsulation, X‐ray diffraction can be performed on the MAPbI 3 films and completed solar cells before and after the different stress conditions. Surprisingly, it is found that the main effect of light soaking and thermal stress is a crystal reorientation with respect to the substrate from (002) to (202) of the perovskite layer, and that this reorientation is accelerated under illumination.