Elucidating the long-range charge carrier mobility in metal halide perovskite thin films

• Published in: Energy & environmental science Vol. 12; no. 1; pp. 169 - 176
• Main Authors: Lim, Jongchul, Hörantner, Maximilian T, Sakai, Nobuya, Ball, James M, Mahesh, Suhas, Noel, Nakita K, Lin, Yen-Hung, Patel, Jay B, McMeekin, David P, Johnston, Michael B, Wenger, Bernard, Snaith, Henry J
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2019
• Subjects: Acetonitrile; Carrier density; Carrier mobility; Charge density; Charge transport; Conduction; Conductivity; Current carriers; Electrical resistivity; Fabrication; Methylamine; Mobility; Optoelectronics; Osmosis; Perovskites; Photovoltaics; Polycrystals; Rangefinding; Thin films; Vapor phases
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c8ee03395a

Many optoelectronic properties have been reported for lead halide perovskite polycrystalline films. However, ambiguities in the evaluation of these properties remain, especially for long-range lateral charge transport, where ionic conduction can complicate interpretation of data. Here we demonstrate a new technique to measure the long-range charge carrier mobility in such materials. We combine quasi-steady-state photo-conductivity measurements (electrical probe) with photo-induced transmission and reflection measurements (optical probe) to simultaneously evaluate the conductivity and charge carrier density. With this knowledge we determine the lateral mobility to be ∼2 cm 2 V −1 s −1 for CH 3 NH 3 PbI 3 (MAPbI 3 ) polycrystalline perovskite films prepared from the acetonitrile/methylamine solvent system. Furthermore, we present significant differences in long-range charge carrier mobilities, from 2.2 to 0.2 cm 2 V −1 s −1 , between films of contemporary perovskite compositions prepared via different fabrication processes, including solution and vapour phase deposition techniques. Arguably, our work provides the first accurate evaluation of the long-range lateral charge carrier mobility in lead halide perovskite films, with charge carrier density in the range typically achieved under photovoltaic operation. A new optoelectronic technique which enables the accurate determination of the long-range lateral charge carrier mobility of metal halide perovskite films.