First Flexible All-Perovskite Tandem Minimodule Using Au-Free Recombination Junction

Abstract

All-perovskite tandem devices are widely studied, as they ensure to overcome the limitations of single-junction devices. However, scaling up the technology into modules on the flexible substrates is a key challenge for commercialization. In this work, strategies are combined to fabricate monolithic 2-terminal all-perovskite tandem (M2TAPT) minimodules on flexible substrates. A methylammonium (MA, CH₃NH₃⁺)-free perovskite formulation leading to a bandgap (E_g) of 1.73 eV is selected and successfully deposited on the flexible substrate. In order to avoid shunts at the interconnections in modules, a thin indium tin oxide recombination layer with high lateral resistivity is developed by DC sputtering. The solvent-barrier property is assisted by a uniform and dense tin oxide (SnO₂) buffer layer grown by atomic layer deposition. Regarding the interconnections of the cells, an appropriate laser scribing process is established in order to achieve a selective and clean removal without affecting the tandem stack. Finally, M2TAPT minimodules are successfully developed on flexible substrates with a geometrical fill factor of 93.8%. A power conversion efficiency of 15.9% is achieved on an active area of 11 cm² with a steady-state efficiency of 15.2% measured after one week of dark storage in the glovebox.