Artikel,

Ternary Organic Solar Cells With 12.8% Efficiency Using Two Nonfullerene Acceptors With Complementary Absorptions

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Advanced Energy Materials, (Februar 2018)
DOI: 10.1002/aenm.201800424

Zusammenfassung

A new small‐molecule acceptor (2,9‐bis(2‐methylene‐(3(1,1‐dicyanomethylene)benzfindanone))7,12‐dihydro‐(4,4,10,10‐tetrakis(4‐hexylphenyl)‐5,11‐diocthylthieno3′,2′:4,5cyclopenta1,2‐bthieno2″,3″:3′,4′cyclopenta1′,2′:4,5thieno2,3‐f1benzothiophene) (NNBDT) based on naphthyl‐fused indanone ending units is reported. This molecule shows a narrow optical bandgap of 1.43 eV and effective absorption in the range of 700–870 nm. The devices based on poly(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo1,2‐b:4,5‐b′dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo1′,2′‐c:4′,5′‐c′dithiophene‐4,8‐dione)) (PBDB‐T):NNBDT yield a power conversion efficiency of 11.7% with a low energy loss of 0.55 eV and a high fill factor (FF) of 71.7%. Another acceptor (2,9‐bis(2‐methylene‐(3(1,1‐dicyanomethylene)benzfindanone))7,12‐dihydro‐4,4,7,7,12,12‐hexaoctyl‐4H‐cyclopenta2″,1″:5,6;3″,4″:5′,6′diindeno1,2‐b:1′,2′‐b′dithiophene (FDNCTF) is introduced as the third component to fabricate ternary devices. The two acceptors (NNBDT and FDNCTF) possess complementary absorption, same molecular orientation, and well‐miscible behavior. It is found that there exists a nonradiative energy transfer process from FDNCTF to NNBDT. The fullerene‐free ternary cells based on PBDB‐T:NNBDT:FDNCTF achieve a high efficiency of 12.8% with an improved short circuit current near 20 mA cm−2 in contrast to the binary devices. The result represents the best performance for fullerene‐free ternary solar cells reported to date and highlights the potential of ternary solar cells. A new acceptor–donor–acceptor type nonfullerene acceptor NNBDT using (2‐3‐oxo‐2,3‐dihydro‐1H‐cyclopentabnaphthalen‐1‐ylidene)malononitrile ending unit is reported. Binary devices based on PBDB‐T:NNBDT give a PCE of 11.7%. Furthermore, the ternary cells using NNBDT and FDNCTF acceptors achieve a performance of 12.8% with energy loss below 0.60 eV, which represents the highest result for fullerene‐free ternary cells reported to date.

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