Below the Urbach Edge: Solar Cell Loss Analysis Based on Full External Quantum Efficiency Spectra

by Jakub Holovsky, Katarína Ridzonová, Amalraj Peter Amalathas, Brianna Conrad, Rupendra Kumar Sharma, Xin Yu Chin, Ebin Bastola, Khagendra Bhandari, Randy J Ellingson, Stefaan De Wolf
Letter Year: 2023 DOI:


Holovský, J., Ridzonová, K., Peter Amalathas, A., Conrad, B., Kumar Sharma, R., Chin, Y., Bastola, E., Bhandari, K., J. Ellingson, R., De Wolf, S. 


We suggest a new solar cell loss analysis using the external quantum efficiency (EQE) measured with sufficiently high sensitivity to also account for defects. Unlike common radiative-limit methods, where the impact of deep defects is ignored by exponential extrapolation of the Urbach absorption edge, our loss analysis considers the full EQE including states below the Urbach edge and uses corrections for band-filling and light-trapping. We validate this new metric on a whole range of photovoltaic materials and verify its accuracy by electrical simulations. Any deviations between the new metric and experimental open-circuit voltage are due to the presence of spatially localized defects and are explained as violations of the assumption of flat quasi-Fermi levels through the device.


Absorption Defects External quantum efficiency Solar cells Thickness