Guo Zhi, Manser Joseph S, Wan Yan, Kamat Prashant V, Huang Libai
Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
1] Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA [2] Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Nat Commun. 2015 Jun 23;6:7471. doi: 10.1038/ncomms8471.
Charge carrier diffusion coefficient and length are important physical parameters for semiconducting materials. Long-range carrier diffusion in perovskite thin films has led to remarkable solar cell efficiencies; however, spatial and temporal mechanisms of charge transport remain unclear. Here we present a direct measurement of carrier transport in space and in time by mapping carrier density with simultaneous ultrafast time resolution and ∼50-nm spatial precision in perovskite thin films using transient absorption microscopy. These results directly visualize long-range carrier transport of ∼220 nm in 2 ns for solution-processed polycrystalline CH3NH3PbI3 thin films. Variations of the carrier diffusion coefficient at the μm length scale have been observed with values ranging between 0.05 and 0.08 cm(2) s(-1). The spatially and temporally resolved measurements reported here underscore the importance of the local morphology and establish an important first step towards discerning the underlying transport properties of perovskite materials.
电荷载流子扩散系数和长度是半导体材料的重要物理参数。钙钛矿薄膜中的长程载流子扩散已带来了显著的太阳能电池效率；然而，电荷传输的空间和时间机制仍不清楚。在此，我们通过使用瞬态吸收显微镜，以超快时间分辨率和钙钛矿薄膜中约50纳米的空间精度同时绘制载流子密度，对空间和时间上的载流子传输进行了直接测量。这些结果直接可视化了溶液处理的多晶CH3NH3PbI3薄膜在2纳秒内约220纳米的长程载流子传输。已观察到在微米长度尺度上载流子扩散系数的变化，其值在0.05至0.08厘米²秒⁻¹之间。此处报道的空间和时间分辨测量结果强调了局部形态的重要性，并朝着识别钙钛矿材料潜在传输特性迈出了重要的第一步。
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