Rapid thermal annealing of CH3NH3PbI3 perovskite thin films by intense pulsed light with aid of diiodomethane additive†

Abstract

The organic metal halide perovskite material is capable of high throughput manufacturing via traditional deposition processes used in roll-to-roll, yet thermal annealing post deposition may require long ovens. We report rapid annealed perovskite thin films using intense pulsed light (IPL) to initiate a radiative thermal response that is enabled by an alkyl halide additive that collectively improves the performance of a device processed in an ambient environment from a baseline of 10 to 16.5% efficiency. Previous reports on CH₃NH₃PbI₃ perovskite films using IPL processing achieved functional devices in milli-second time scales and are promising for high throughput manufacturing processes under ambient conditions. In this study, we found that the addition of diiodomethane (CH₂I₂) as an additive to the methylammonium iodide (MAI)/lead iodide (PbI₂) precursor ink chemistry and subsequent IPL thermal annealing are inter-dependent. The concentration of CH₂I₂ and IPL processing parameters have a direct effect on the surface morphology of the films and performance within a perovskite solar cell (PSC). The CH₂I₂ dissociates under exposure to ultraviolet (UV) radiation from the IPL source liberating iodine ions in the film, influencing the perovskite formation and reducing the defect states. We anticipate that these results can be utilized to further develop different ink formulations using alkyl halides for the IPL technique to improve the performance of perovskite solar cells processed in ambient conditions.