Air-Stable Molecular Semiconducting Iodosalts for Solar Cell Applications: Cs2SnI6 as a Hole Conductor

• Published in: Journal of the American Chemical Society Vol. 136; no. 43; pp. 15379 - 15385
• Main Authors: Lee, Byunghong, Stoumpos, Constantinos C, Zhou, Nanjia, Hao, Feng, Malliakas, Christos, Yeh, Chen-Yu, Marks, Tobin J, Kanatzidis, Mercouri G, Chang, Robert P. H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29-10-2014
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja508464w

We introduce a new class of molecular iodosalt compounds for application in next-generation solar cells. Unlike tin-based perovskite compounds CsSnI3 and CH3NH3SnI3, which have Sn in the 2+ oxidation state and must be handled in an inert atmosphere when fabricating solar cells, the Sn in the molecular iodosalt compounds is in the 4+ oxidation state, making them stable in air and moisture. As an example, we demonstrate that, using Cs2SnI6 as a hole transporter, we can successfully fabricate in air a solid-state dye-sensitized solar cell (DSSC) with a mesoporous TiO2 film. Doping Cs2SnI6 with additives helps to reduce the internal device resistance, improving cell efficiency. In this way, a Z907 DSSC delivers 4.7% of energy conversion efficiency. By using a more efficient mixture of porphyrin dyes, an efficiency near 8% with photon confinement has been achieved. This represents a significant step toward the realization of low-cost, stable, lead-free, and environmentally benign next-generation solid-state solar cells.