Mitigating Iodine Diffusion by a MoO3–Organic Composite Hole Transport Layer for Stable Perovskite Solar Cells

Halide perovskite solar cells (PSCs) exhibit commercialization potential, but long-term stability still must be addressed. Among various products of perovskite decomposition, iodine species are of considerable concern due to their high vapor pressure and corrosive nature. To address this, a small-molecule hole transport layer (HTL), 4,4′,4″-tris(3-methylphenyl)phenylaminotriphenylamine (m-MTDATA), is used; mixing it with molybdenum trioxide (MoO3) p-dopes the layer and slows iodine permeation. We demonstrate that m-MTDATA:MoO3 HTLs employed in PSCs improve stability under both thermal and voltage bias stress compared to devices with a conventional doped 2,2′,7,7′-tetrakisN,N-di(4-methoxyphenyl)amino-9,9′-spirobifluorene (spiro-OMeTAD) HTL.