Impact of Tetrakis(dimethylamido)tin(IV) Degradation on Atomic Layer Deposition of Tin Oxide Films and Perovskite Solar Cells

Abstract Tin oxide (SnO x ) films synthesized by atomic layer deposition (ALD) are widely explored in a range of optoelectronic devices including electrochemical sensors, transistors, and photovoltaics. However, the integrity of the key ALD‐SnO x precursor, namely tetrakis(dimethylamido)tin (IV) (TDMASn), and its influence on the properties of ultimate films remain unexplored. Here a significant degradation of TDMASn into bis(dimethylamido)tin(II) via the Sn‐imine complex is reported, and its impact on the corresponding films and devices is examined. It is found, surprisingly, that this degradation does not affect the growth kinetics and morphology of ALD‐SnO x films. But it notably deteriorates their electronic properties, resulting in films with twice the electrical resistance due to different oxidation mechanisms of the degradation products. Perovskite solar cells employing such films exhibit a significant loss in power conversion efficiency, primarily due to charge transport and transfer losses. These findings urge strategies to stabilize TDMASn, a critical precursor for ALD‐SnO x films, or to identify alternative materials to achieve efficient and reliable devices.