Requirements for Making Thick Junctions of Organic Solar Cells based on Nonfullerene Acceptors

Organic bulk-heterojunction solar cells based on the newly developed nonfullerene electron acceptors have potential for very low-cost energy production. However, to enable large-scale production with common printing techniques, active layer thicknesses need be increased by up an order of magnitude, which is currently not possible without significant loss in performance. Herein, requirements making acceptor (NFA)-based thick layers and high efficiencies are clarified. The charge carrier mobility, unintentional doping concentrations, bimolecular recombination prefactor model high-efficiency system PM6 (Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b?]dithiophene))-alt-(5,5-(1?,3?-di-2-thienyl-5?,7?-bis(2-ethylhexyl)benzo[1?,2?-c:4?,5?-c?]dithiophene-4,8-dione)]):Y6 (2,2?-((2Z,2?Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2?,3?:4?,5?]thieno[2?,3?:4,5]pyrrolo[3,2-g]thieno[2?,3?:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) determined. results implemented a combined electro-optical device model, used determine effect varying these parameters efficiency. show that mobility imbalance can lead improved performance at large thicknesses, partially contradicting previous studies performed fullerene-based systems. findings highlight importance determining hole mobilities selectively, as well characterizing concentrations.