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arXiv · 1511.07887

Transient terahertz photoconductivity measurements of minority-carrier lifetime in tin sulfide thin films: Advanced metrology for an early-stage photovoltaic material

R. Jaramillo·Meng-Ju Sher·Benjamin K. Ofori-Okai·V. Steinmann·Chuanxi Yang·Katy Hartman·Keith A. Nelson·Aaron M. Lindenberg·Roy G. Gordon·T. Buonassisi
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Abstract

Materials research with a focus on enhancing the minority-carrier lifetime of the light-absorbing semiconductor is key to advancing solar energy technology for both early-stage and mature material platforms alike. Tin sulfide (SnS) is an absorber material with several clear advantages for manufacturing and deployment, but the record power conversion efficiency remains below 5%. We report measurements of bulk and interface minority-carrier recombination rates in SnS thin films using optical-pump, terahertz (THz)-probe transient photoconductivity (TPC) measurements. Post-growth thermal annealing in H_2S gas increases the minority-carrier lifetime, and oxidation of the surface reduces the surface recombination velocity. However, the minority-carrier lifetime remains below 100 ps for all tested combinations of growth technique and post-growth processing. Significant improvement in SnS solar cell performance will hinge on finding and mitigating as-yet-unknown recombination-active defects. We describe in detail our methodology for TPC experiments, and we share our data analysis routines as freely-available software.

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R. Jaramillo, Meng-Ju Sher, Benjamin K. Ofori-Okai, V. Steinmann, Chuanxi Yang, Katy Hartman, Keith A. Nelson, Aaron M. Lindenberg, Roy G. Gordon, T. Buonassisi. 2015-11-24. Transient terahertz photoconductivity measurements of minority-carrier lifetime in tin sulfide thin films: Advanced metrology for an early-stage photovoltaic material. https://doi.org/10.1063/1.4940157

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