Enhancement of Morphological and Optoelectronic Properties of Perovskite Films by CH3NH3CI Treatment for Efficient Solar Minimodules

In order to get homogeneous and high-quality perovskite CH3NH3PbI3 films, different growing methods have been developed, but most of them are unsuitable for scaling up. In this work, we studied in a systematic approach the influence of CH3NH3CI (MACI) surface treatment in the acetonitrile (ACN) deposition route. This method does not require vacuum nor solvent quenching steps, which make it probably one of the easiest for transference from lab scale to large-area deposition techniques such as roll-to-roll printing. The properties of perovskite films grown by ACN method and the influence of the MAC1 on the performance of the perovskite solar cells (PSCs) are characterized in detail by different techniques. By atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) we found significant differences in the morphology and the work function of the perovskite with and without MACI treatment. Moreover, the microstructure presents very different behavior: after being exposed to radiation, the MACI treated sample presented passivated grain boundaries and higher intensity in the photoluminescence (PL) emission. The higher PL for perovskite films with MAC! treatment correlates with superior photovoltaic parameters of PSCs. All these features lead to highly homogeneous perovskite layers on large areas enabling the fabrication of 10 X 10 cm(2) solar minimodules processed in air at low temperature (<100 C). For these minimodules, we reached a PCE up to 9.2% with an aperture area of 40 cm2. These results demonstrate the potential of perovskite surface treatments as an effective strategy for the production of smooth, pinhole free films on large-area substrates, the gateway for further scale-up and commercialization.