Photovoltaics have the potential to convert sunlight into electricity at very large scales and at low cost. However, many constraints on materials and interfaces must be simultaneously satisfied to achieve high efficiency. For example, light absorption by photovoltaic absorber materials generates electron-hole pairs that must be separated and collected before they recombine. For many materials, recombination lifetimes are on the order of picoseconds to nanoseconds. This talk will highlight our group’s use of ultrafast spectroscopy to provide a link between processing, structure, and device performance that can help direct the design of more efficient solar cells. Specifically, we have combined time resolved terahertz spectroscopy and transient absorption spectroscopy with modeling of the semiconductor transport equations to extract carrier lifetimes and mobilities and to determine dominant recombination mechanisms. I will discuss our application of this method to understand the dependence of ultrafast dynamics on: (1) composition and surface treatments in kesterite Cu2ZnSn(S,Se)4 (CZTSSe) thin films and single crystals, and (2) inorganic versus organic A-site cations in lead halide perovskite (CsPbI3, MAPbI3) thin films.

Ultrafast carrier dynamics in kesterite and perovskite photovoltaic absorber materials

256th National Meeting (2018)

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