From Efficient Charge Separation to Suppressed Charge Recombination in Single-component Organic Solar Cells

Single-component organic solar cells based on double cable polymers have achieved remarkable performance, with DCPY2 reaching a high efficiency of over 13%. DCPY2 shows a reduced recombination rate compared to their binary counterpart (PBDB-T:Y-O6). This slower recombination in DCPY2 is attributed to the reduced wavefunction overlap of delocalized charges, achieved by spatially separating the donor and acceptor units with an alkyl linker, thereby restricting the recombination pathways. We further fluorinated both donor and acceptor of DCPY2 into DCPY2-F with an efficiency over 14%. DCPY2-F shows an efficient charge generation process with higher short-circuit current and higher efficiency. From Pump-push probe results, the improved charge separation efficiency is benefited from the flatter energetic landscape between interface and the bulk. We attribute the faster charge transfer process to the more energetically ordered interfacial CT states in DCPY2-F. These findings draw a comprehensive understanding from charge generation to charge recombination in single component organic soar cells