Triple-cation perovskite solar cells fabricated by a hybrid PVD/blade coating process using green solvents

At present, the perovskite absorber layers of the state-of-the-art, large-area perovskite solar modules are fabricated by either scalable solution- or vapour-based deposition methods. Solution-based deposition methods easily allow to incorporate different organic and inorganic precursors to tune the band gap by compositional engineering¹. However, such methods usually rely on toxic solvents like dimethylformamide (DMF) during the fabrication of the perovskite absorber layer ². In contrast, the fabrication of vapour-based perovskite absorber layer copes without any solvents. However, compositional engineering is complex and challenging to carry out, as organic and inorganic precursors have different vapour pressures, which requires to decouple the depositions of organic and inorganic precursors ^3,4. Moreover, the implementation of passivation strategies is challenging as well ⁵. Therefore, it is required to develop an industrial-scalable fabrication process of the perovskite absorber layer, that combines the merits of solution- and vapour-based deposition methods.

In this contribution, we report a novel, industrial-scalable fabrication process of the perovskite absorber, that allows facile tuning of composition and employ non-toxic solvents. It combines scalable vapour- and solution-based deposition methods to fabricate efficient perovskite solar cells (PSC) on 50 mm x 50 mm substrates. First, the inorganic halide precursors are deposited by physical vapour deposition (PVD) to circumvent any usage of toxic solvents. Second, the organic halide precursors are dissolved in isopropanol and blade coated onto the previously evaporated inorganic halide film to obtain efficient and compact perovskite absorbers after annealing. The triple-cation mixed halide perovskite absorber layers have an optical band gap of 1.56 eV. To complete the small-area devices, we further deposited both charge transport layers by blade coating. All blade coating depositions are carried out in ambient air and do not involve toxic solvents. The final small-area devices (10 mm²) achieved open-circuit voltages (V_OC) of 1.16 V and PCEs up to 18.7 %.

In conclusion, the presented hybrid PVD/blade fabrication process achieved efficient and uniform PSCs. The fabrication process is industrial-scalable and uses green solvents only. It further allows compositional engineering and a facile implementation of passivation strategies. Further investigations are needed to improve the morphology and crystal’s uniformity of the perovskite absorber layer fabricated by PVD/blade.