Ternary organic solar cells with small voltage losses (Conference Presentation)

The voltage loss in organic photovoltaics (OPVs) is defined as the difference between the open circuit voltage and the voltage offset between the lowest unoccupied molecular orbital (LUMO) of the acceptor and the highest occupied MO (HOMO) of the donor forming the charge dissociating heterojunction. Widely employed fullerene acceptors show significant voltage losses, approaching 0.8 V, thereby reducing the potential efficiencies of OPVs. In this work, we show that ternary blends of two non-fullerene acceptors with a polymer donor are effective in significantly reducing the voltage losses in near-infrared (NIR) OPVs. A narrow energy gap non-fullerene acceptor, FIDC, sharing similar HOMO energies with the acceptor BT-CIC [1], (absorption up to 1000 nm) is blended with the polymer PCE-10. The power conversion efficiency (PCE) of the ternary cell is increased from 10.7% in a BT-CIC:PCE-10 binary cell to 12.6% in the BT-CIC:FIDC:PCE-10 ternary cell. Further, the short-circuit current density is increased from 22.3 mA cm-2 to 25.5 mA cm-2. Importantly, the ternary cell decreased the voltage loss from 0.61 to 0.54 V. The ternary devices showed larger open circuit voltage of 0.70V than either the analogous BT-CIC (0.69 V) or FIDC (0.66 V) binary devices [2,3]. This work points to a simple means for increasing the materials available for spanning the visible and NIR spectra in very high efficiency, low loss OPVs. 1. Li, Y.; Lin, J.-D.; Che, X.; Qu, Y.; Liu, F.; Liao, L.-S.; Forrest, S. R. J. Am. Chem. Soc. 2017, 139, 17114. 2. Ameri, T.; Khoram, P.; Min, J.; Brabec, C. J. Adv. Mater. 2013, 25, 4245. 3. Fu, H.; Wang, Z.; Sun, Y. Solar RRL 2018, 2, 1700158.