Improved performance and stability of hole-conductor-free mesoporous perovskite solar cell with new amino-acid iodide cations

Carbon-based and hole-transporting-material-free perovskite solar cells (PSCs) are a promising alternative structure for low-cost applicable method to their manufacturing. However, in this technology, the presence of 5-ammonium valeric acid iodide (5-AVAI) as co-cation to the commonly used MAPbI₃ perovskite is necessary which promotes the crystal nucleation and growth within TiO₂/ZrO₂ mesoscopic oxide scaffold, while affects the contact of perovskite with hydrophobic carbon electrodes. Herein, we present the use of alternative and very low-cost amino acids with comparable and even better performance in some cases of as-used 5-AVAI. On that purpose, two common amino acids of dl-leucine and dl-alanine are used for the synthesis of their iodide derivatives also performed as co-cation with methyl ammonium iodide into the MAPbI₃. The structural, optical, and electrical characteristics of the PSCs prepared with newly presented amino acids are examined in comparison with those obtained for (5-AVA)_xMA_1–xPbI₃ perovskite as a reference. In the case of dl-leucine iodide-based perovskite, enhanced stability and performance over 5-AVAI was monitored to their PSCs for over 120 days referring to unsealed devices under 60% relative humidity.