Selenophene-Containing Small-Molecule Donor with a Medium Band Gap Enables High-Efficiency Ternary Organic Solar Cells.

To construct efficient donor:donor:acceptor (D1:D2:A)-type ternary devices, two new selenophene-containing small-molecule (SM) donors named FSBTSeEHR and FSBTSeHR have been designed and synthesized that show broader and red-shifted absorption spectra than the thiophene analogues. With the introduction of SM donors into the D18:CH-6F host system, enhanced light harvesting and charge transport were achieved, benefiting from more complementary absorptions and cascaded energy levels. Furthermore, the doping of the SM donor could effectively modulate the micromorphology and enable a more suitable phase separation size in the active layer. After systematic optimization, the FSBTSeEHR-based ternary organic solar cell (TOSC) exhibited an excellent power conversion efficiency (PCE) of 18.02% with a high open-circuit voltage (Voc) of 0.905 V, short-circuit current density (Jsc) of 26.41 mA cm-2, and fill factor (FF) of 0.754. By contrast, the FSBTSeHR counterpart showed a superior efficiency of 18.55% due to the higher Jsc (26.91 mA cm-2) and FF (0.761). The outstanding PCEs of D1:D2:A-type TOSCs based on our SM donors, FSBTSeEHR and FSBTSeHR, are significantly higher than those of the corresponding binary host system (16.86%) and among the highest values reported to date. This work demonstrates that D1:D2:A-type TOSCs have tremendous potential to achieve superior performances through elaborate design of the SM donor guest and reasonable combination of D and A ingredients.

All-Small-Molecule Organic Solar Cells Based on a Fluorinated Small Molecule Donor With High Open-Circuit Voltage of 1.07 V.

A new small molecule donor with an acceptor-donor-acceptor (A-D-A) structure, namely DRTB-FT, has been designed and synthesized for all-small-molecule organic solar cells (ASM-OSCs). By introducing fluorine atoms on the thienyl substituent of the central benzodithiophene unit, DRTB-FT shows a low-lying highest occupied molecular orbital (HOMO) energy level of -5.64 eV. Blending with an A-D-A type acceptor F-2Cl, DRTB-FT based ASM-OSCs gave a power conversion efficiency (PCE) of 7.66% with a high open-circuit voltage (V oc) of 1.070 V and a low energy loss of 0.47 eV. The results indicate that high V oc of ASM-OSC devices can be obtained through careful donor molecular optimization.

A New Nonfullerene Electron Acceptor with a Ladder Type Backbone for High-Performance Organic Solar Cells.

Nonfullerene acceptor FDICTF (2,9-bis(2methylene-(3-(1,1-dicyanomethylene)indanone))-7,​12-​dihydro-​4,​4,​7,​7,​12,​12-​hexaoctyl-​4H-​cyclopenta[2″,​1″:5,​6;3″,​4″:5',​6']​diindeno[1,​2-​b:1',​2'-​b']dithiophene) modified by fusing the fluorene core in a precursor, yields 10.06% high power conversion efficiency, and demonstrates that the ladder and fused core backbone in A-D-A structure molecules is an effective design strategy for high-performance nonfullerene acceptors.