Spatial and temporal imaging of long-range charge transport in perovskite thin films by ultrafast microscopy

• Published in: Nature communications Vol. 6; no. 1; p. 7471
• Main Authors: Guo, Zhi, Manser, Joseph S., Wan, Yan, Kamat, Prashant V., Huang, Libai
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23-06-2015; Nature Publishing Group; Nature Pub. Group
• Subjects: 140/125; 639/301/930/2735; 639/624/1107/328; 639/766/119/544; 639/766/25; applied physics; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Humanities and Social Sciences; imaging techniques; microscopy; multidisciplinary; Science; science & technology - other topics; Science (multidisciplinary); surfaces, interfaces and thin films
• ISSN: 2041-1723; 2041-1723
• 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 CH
3
NH
3
PbI
3
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.
Determining the mechanism of charge carrier transport in solar cells is important for their development towards higher efficiencies. Here, the authors elucidate the spatial and temporal diffusion of charge carriers in hybrid perovskite thin films through ultrafast transient absorption microscopy.