Predicting solar cell performance from terahertz and microwave spectroscopy
Hannes Hempel, Edwin J. Heilweil, Timothy Magnanelli
Mobilities and lifetimes of photogenerated charge carriers are core properties of photovoltaic materials and can both be characterized by contactless terahertz or microwave measurements. Previously reported values for lead-halide perovskites vary by orders of magnitude, meriting concerns whether terahertz and microwave measurements can accurately estimate the implied solar cell performance. Therefore, the expertise from fifteen laboratories is combined to understand the impact of measurement conditions, alternate analyses, and common pitfalls using a (Cs,FA,MA)Pb(I,Br)3 halide perovskite thin film as case study. At 1 sun equivalent excitation, no significant exciton formation and trapping were observed. Terahertz, microwave and photoluminescence transients for the neat material yielded consistent effective lifetimes implying a resistance-free JV-curve with a potential power conversion efficiency of 24.6 %. For grainsizes above 20 nm, intra-grain charge transport is characterized by terahertz mobilities that translate into equal electron and holes mobilities of 16 cm2V-1s-1. Drift-diffusion simulations indicate that these intra-grain mobilities can slightly reduce the fill factor of the solar cell to 0.82, in accordance with the best-realized devices in the literature. A best practice for terahertz and microwave characterization of photovoltaic materials is presented, and laboratories are invited to cross-calibrate setups to ensure reliable reporting of mobility values for emerging materials.
, Heilweil, E.
and Magnanelli, T.
Predicting solar cell performance from terahertz and microwave spectroscopy, Advanced Energy Materials, [online], https://doi.org/10.1002/aenm.202102776, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933316
(Accessed September 23, 2023)