Spontaneous Defect Annihilation in CH3NH3PbI3 Thin Films at Room Temperature Revealed by Time-Resolved Photoluminescence Spectroscopy

• Published in: The journal of physical chemistry letters Vol. 6; no. 3; pp. 482 - 486
• Main Authors: Yamada, Yasuhiro, Endo, Masaru, Wakamiya, Atsushi, Kanemitsu, Yoshihiko
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 05.02.2015
• Subjects: carrier trapping; photocarrier lifetime; optical characterization; nonradiative recombination; photovoltaics
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz5026596

We utilized time-resolved photoluminescence (PL) spectroscopy to investigate the photocarrier recombination dynamics in CH3NH3PbI3 thin films as a function of the time elapsed from the film’s fabrication. We found that the PL lifetime gradually increased and began to level out once the age of the film reached ∼30 h. Even under weak excitation, the PL dynamics depended on the excitation intensity in the fresh sample, while the mature sample displayed no excitation-intensity dependence associated with the PL dynamics. We submit that this can be explained by the fact that a significant number of defects are initially formed in CH3NH3PbI3 thin films fabricated by the sequential method and are spontaneously reduced by room-temperature annealing. Our results provide important insights for reducing the nonradiative recombination centers, which improves the power conversion efficiency of perovskite solar cells.