Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses.
Intrinsic non-radiative voltage losses in fullerene-based organic solar cells / Benduhn, J., Tvingstedt, K., Piersimoni, F., Ullbrich, S., Fan, Y.l., Tropiano, M., Mcgarry, K.a., Zeika, O., Riede, M.k., Douglas, C.j., Barlow, S., Marder, S.r., Neher, D., Spoltore, D., Vandewal, K.. - In: NATURE ENERGY. - ISSN 2058-7546. - 2:6(2017). [10.1038/nenergy.2017.53]
Intrinsic non-radiative voltage losses in fullerene-based organic solar cells
Spoltore D;
2017-01-01
Abstract
Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
