Batch-Reproducible and Thickness-Insensitive Mesopolymer Zwitterion Interlayers for Organic Solar Cells

Zwitterionic polymers or small molecules are a classof widelyused interlayer materials in organic solar cells (OSCs). It is challengingto develop such materials that combine good film-forming property,high batch-to-batch reproducibility, and broad thickness processingwindow in device applications. Herein, we designed and synthesizedtwo self-doped conjugated mesopolymer zwitterions (CMZs), namely, MT ( 2 ) PDIMz and MT ( 2 ) PDINz (PDI = perylene-diimide,M = mesopolymer, T-2 = dithiophene, Mz = imidazolium zwitterion,Nz = ammonium zwitterion). Both show good processability and effectivelyreduce the work function of metal electrodes. The substitution ofimidazolium cations with ammonium cations on the side-chains can furthermodulate the solution assembly and self-doping effect of CMZs, enablingimproved interfacial compatibility with active layers and higher electronmobility in MT ( 2 ) PDIMz. The versatility of CMZs interlayers for OSCs is confirmed withseveral binary and ternary active layers, affording efficiencies upto 19.01%. Notably, over 98% of the optimal efficiency is maintainedas the thickness of the interlayers increases to 40 nm with good reproducibility.