Composition dependent photocarrier dynamics in CH 3 NH 3 Pb(I 1 x Br x 3 thin films
Over the past few years, organo metal halide perovskites have emerged as high potential materials for cost effective solar cell applications due to their excellent optoelectronic characteristics [1] The power conversion efficiency (PCE) of single junction perovskite solar cells increased incredibly, reaching over 20% at present [2] Besides current extensive efforts to improve further the PCE of single junction solar cells, using a perovskite subcell in a tandem structure as a top cell is a promising approach to realize devices with a much higher PCE [3] For such tandem solar cell applications, the band gap energy of and the recombination of photogenerated carriers in the perovskite layer take critical roles in determining the entire photovoltaic operation of a tandem device. The band gap energy of perovskite materials could be tuned flexibly and controllably through adjusting the contents of the halide elements [4] On the other hand, although tremendous studies examining the dynamical optical behaviors of photocarriers in pure halide perovskites have been done [5] understanding of the composition dependent photocarrier recombination dynamics in mixed halide perovskites has remained limited. In this work, we investigate the composition dependence of photocarrier recombination dynamics in CH3NH3Pb(I1 xBrx)3 (MAPb(I,Br)3) perovskite thin films by means of time resolved photoluminescence (PL) and transient absorption (TA) spectroscopy. The PL decay dynamics measured under weak excitation condition reveal an increase in the single carrier trapping rate with increasing the Br content in MAPb(I,Br)3 thin films. Using the obtained single carrier trapping rate, we are then able to evaluate the composition dependences of the two carrier recombination and Auger recombination rates from the excitation dependent TA kinetic traces. We discuss the physical issues behind the composition dependent photocarrier recombination dynamics in MAPb(I,Br)3 and its possible influences on the performance of perovskite solar cells. Part of this work was supported by JST CREST, JSPS KAKENHI (16F16017) and the MEXT Project of Integrated Research on Chemical Synthesis. The work was also funded in part by the Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, under Award Number DE EE0006710. [1] S. D. Stranks, H. J. Snaith, Nat. Nanotech. 10, 391 (2015) [2] M. A. Greeen et al. Prog. Photovolt. 24, 905 (2016) [3] D. P. McMeekin et al. Science 351, 151 (2016) [4] I. L. Braly et al. J. Phys. Chem. C 120, 893 (2016) [5] Y. Yamada et al. J. Am. Chem. Soc. 136, 11610 (2014) J. Am. Chem. Soc. 137, 10456 (2015) L. Q. Phuong et al. J. Phys. Chem. Lett. 7, 2316 (2016) Di 77Hui Ying Yong Wu Li Xue Hui Qiu Ji Xue Shu Jiang Yan Hui Jiang Yan Yu Gao Ji (2016 Zhu Lu metsuse (Xin Xi Xian Xin Xi Shi 15p A41 7