Photocarrier Recombination and Injection Dynamics in Long-Term Stable Lead-Free CH3NH3SnI3 Perovskite Thin Films and Solar Cells

• Published in: Journal of physical chemistry. C Vol. 121; no. 30; pp. 16158 - 16165
• Main Authors: Handa, Taketo, Yamada, Takumi, Kubota, Hirofumi, Ise, Shogo, Miyamoto, Yoshihiro, Kanemitsu, Yoshihiko
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03.08.2017
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b06199

We investigated the near-band-edge optical responses and photocarrier dynamics of encapsulated long-term stable CH3NH3SnI3 (MASnI3) thin films and solar-cell devices. The MASnI3 thin film prepared with SnF2 exhibited a bandgap of 1.25 eV, while the film without SnF2 had a significantly blueshifted absorption edge. On the contrary, the PL peak energies were not influenced by the addition of SnF2. These observations indicate that the blueshift of the absorption edge in the SnF2-free MASnI3 sample is due to the Burstein–Moss shift induced by a significant unintentional hole doping. Furthermore, time-resolved photoluminescence measurements revealed that by adding SnF2 the photocarrier lifetime of the film increased by one order of magnitude, which enables improved device performance of solar cells. We clarified that in the MASnI3 solar cells the short-circuit current stays significantly below the ideal value due to a large nonradiative recombination rate in the perovskite layer, resulting in a small photocarrier-injection efficiency into the charge-transport layers.