講演情報
[16a-PA5-8]Spectroscopic Analysis of Voltage Losses in CIGS and CIGS/Perovskite Tandem Solar Cells
〇(P)Siliang Cao1, Genchi Inohana1, Ryousuke Ishikawa2, Muhammad Monirul Islam1, Takeaki Sakurai1 (1.Univ. of Tsukuba, 2.Tokyo City Univ.)
キーワード：
CIGS、Open-circuit voltage、Quasi-fermi level splitting
CuIn1−xGax(S,Se)2 (CIGS) is a leading thin-film photovoltaic absorber with efficiencies above 23.6%. However, its open-circuit voltage (Voc) remains below the theoretical limit, resulting in a significant voltage deficit.
We establish a PL/EL-based theoretical framework that links quasi-Fermi level splitting (QFLS) with sub-bandgap absorptivity to determine the maximum achievable Voc in the radiative limit for CIGS solar cells. By adopting the Katahara–Hillhouse model, PL spectra are quantitatively interpreted with explicit consideration of band-tail states. Owing to compositional disorder and pronounced band-tail states in CIGS absorbers, simplified logarithmic analyses often lead to inaccuracies; therefore, QFLS and absorption-tail parameters are evaluated simultaneously to properly capture the disordered nature of the material.
The extracted parameters, including the bandgap energy (Eg), temperature (T), Urbach energy (EU), and quasi-Fermi level splitting (Δμ), show good quantitative agreement with previously reported values, validating the applicability of the model. By explicitly incorporating tail-state energetics, a lower and more accurate radiative-limit Voc is obtained, enabling a more reliable determination of voltage losses across different CIGS devices, typically within 20 meV. Based on this spectroscopic framework, the approach is further extended to CIGS/perovskite tandem solar cells, where maintaining consistent PL/EL-derived indices across sub-cells is essential for identifying the origin of Voc losses and establishing Voc accumulation. Finally, recombination losses are quantitatively evaluated from spectroscopic indicators as direct evidence of Voc deficits, clarifying the physical bottlenecks and design guidelines for improving the performance of CIGS and CIGS/perovskite tandem solar cells.
We establish a PL/EL-based theoretical framework that links quasi-Fermi level splitting (QFLS) with sub-bandgap absorptivity to determine the maximum achievable Voc in the radiative limit for CIGS solar cells. By adopting the Katahara–Hillhouse model, PL spectra are quantitatively interpreted with explicit consideration of band-tail states. Owing to compositional disorder and pronounced band-tail states in CIGS absorbers, simplified logarithmic analyses often lead to inaccuracies; therefore, QFLS and absorption-tail parameters are evaluated simultaneously to properly capture the disordered nature of the material.
The extracted parameters, including the bandgap energy (Eg), temperature (T), Urbach energy (EU), and quasi-Fermi level splitting (Δμ), show good quantitative agreement with previously reported values, validating the applicability of the model. By explicitly incorporating tail-state energetics, a lower and more accurate radiative-limit Voc is obtained, enabling a more reliable determination of voltage losses across different CIGS devices, typically within 20 meV. Based on this spectroscopic framework, the approach is further extended to CIGS/perovskite tandem solar cells, where maintaining consistent PL/EL-derived indices across sub-cells is essential for identifying the origin of Voc losses and establishing Voc accumulation. Finally, recombination losses are quantitatively evaluated from spectroscopic indicators as direct evidence of Voc deficits, clarifying the physical bottlenecks and design guidelines for improving the performance of CIGS and CIGS/perovskite tandem solar cells.