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Dopant-Free Tetrakis-Triphenylamine Hole Transporting Material for Efficient Tin-Based Perovskite Solar Cells

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journal contribution
posted on 06.12.2017, 00:00 by Weijun Ke, Pragya Priyanka, Sureshraju Vegiraju, Constantinos C. Stoumpos, Ioannis Spanopoulos, Chan Myae Myae Soe, Tobin J. Marks, Ming-Chou Chen, Mercouri G. Kanatzidis
Developing dopant-free hole transporting layers (HTLs) is critical in achieving high-performance and robust state-of-the-art perovskite photovoltaics, especially for the air-sensitive tin-based perovskite systems. The commonly used HTLs require hygroscopic dopants and additives for optimal performance, which adds extra cost to manufacturing and limits long-term device stability. Here we demonstrate the use of a novel tetrakis-triphenylamine (TPE) small molecule prepared by a facile synthetic route as a superior dopant-free HTL for lead-free tin-based perovskite solar cells. The best-performing tin iodide perovskite cells employing the novel mixed-cation ethylenediammonium/formamidinium with the dopant-free TPE HTL achieve a power conversion efficiency as high as 7.23%, ascribed to the HTL’s suitable band alignment and excellent hole extraction/collection properties. This efficiency is one of the highest reported so far for tin halide perovskite systems, highlighting potential application of TPE HTL material in low-cost high-performance tin-based perovskite solar cells.