Bottom-up nucleation induced conformal crystallization for inverted MA-free perovskite solar cells on textured substrates

Utilizing textured fluorine-doped tin oxides (FTO) as transparent conductive oxide (TCO) substrates is advantageous for capturing incident light, thereby enhancing the power photoelectric conversion efficiency (PCE) of inverted perovskite solar cells (PSCs). However, the roughness of these substrates and uncontrolled nucleation often results in voids at the perovskite-buried surface, leading to insufficient charge extraction and serving as degradation initiation points. This study introduces ( S )-3-amino-4-(4-chlorophenyl)butyric acid hydrochloride (AbaCl), which binds to FTO through its anchor group (–COOH) at the deficient regions of MeO-4PACz. Moreover, the chlorine end molecules offer active sites for nucleation by forming halogen bonds with undercoordinated iodide ions (I − ). AbaCl also interacts with formamidinium (FA + ) in perovskite precursor solution via hydrogen bonding, promoting crystallization at the buried interface. Consequently, nucleation at this buried interface becomes preferential, ensuring bottom-up growth and preventing voids formation due to incomplete solvent evaporation, allowing the perovskite layer to conformally adhere to the substrate without gaps. As a result, the AbaCl-treated inverted PSCs achieved a champion PCE of 24.50 % and exhibited enhanced operational stability. This work presents a method for conformally growing perovskite films on textured substrates to produce efficient and stable PSCs.