Resolving a Critical Instability in Perovskite Solar Cells by Designing a Scalable and Printable Carbon Based Electrode-Interface Architecture

Thin-film solar cells based on hybrid organo-halide lead perovskites achieve over 22% power conversion efficiency (PCE). A photovoltaic technology at such high performance is no longer limited by efficiency. Instead, lifetime and reliability become the decisive criteria for commercialization. This requires a standardized and scalable architecture which does fulfill all requirements for larger area solution processing. One of the most highly demanded technologies is a low temperature and printable conductive ink to substitute evaporated metal electrodes for the top contact. Importantly, that electrode technology must have higher environmental stability than, for instance, an evaporated silver (Ag) electrode. Herein, planar and entirely low-temperature-processed perovskite devices with a printed carbon top electrode are demonstrated. The carbon electrode shows superior photostability compared to reference devices with an evaporated Ag top electrode. As hole transport material, poly (3' hexyl thiophene) (P3HT) and copper(I) thiocyanate (CuSCN), two cost-effective and commercially available p-type semiconductors are identified to effectively replace the costlier 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)9,9'-spirobifluorene (spiro-MeOTAD). While methylammonium lead iodide (MAPbI(3))-based perovskite solar cells (PSCs) with an evaporated Ag electrode degrade within 100 h under simulated sunlight (AM 1.5), fully solution-processed PSCs with printed carbon electrodes preserve more than 80% of their initial PCE after 1000 h of constant illumination.