- AMER CHEMICAL SOC
We investigated the near-band-edge optical responses and photocarrier dynamics of encapsulated long-term stable CH3NH3SnI3 (MASnI(3)) thin films and solar-cell devices. The MASnI(3) 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 MASnI(3) 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.
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