Suppressed charge recombination in polymer solar cells based on perylene diimide derivative acceptors via solvent vapor annealing

• A blend of P(IID-DTC):di-PBI is used to fabricate polymer solar cells.
• The absorption of blends exhibits full coverage of 400–750 nm to solar spectrum.
• Dominated bimolecular recombination is suppressed by using CH2Cl2 vapor annealing.
• The electron mobility is enhanced by more than two orders of magnitude.
• The P(IID-DTC):di-PBI polymer solar cell shows a PCE of 2.95%.

A singly-linked perylene bisimide dimer (di-PBI) and a low band gap polymer based on dithienocarbazole and isoindigo moieties (P(IID-DTC)) are selected as electron acceptor and donor respectively to fabricate non-fullerene based polymer solar cells. The combination of di-PBI acceptor and P(IID-DTC) donor provides well overlapped absorption profile with solar light in the visible region. The P(IID-DTC):di-PBI blend morphology and its effect on charge transport and recombination have been investigated in detail. The dominant bimolecular recombination in commonly processed P(IID-DTC):di-PBI blend results in a low power conversion efficiency of merely 1%. We find that CH2Cl2 vapor annealing can effectively improve bi-continuous phase separation and boost the electron transport by more than two orders of magnitude due to the detrap of di-PBI molecules from amorphous P(IID-DTC) matrix. More importantly, the dominant bimolecular recombination in the P(IID-DTC):di-PBI blend films is strongly suppressed. Finally, the power conversion efficiency of non-fullerene P(IID-DTC):di-PBI blend solar cell is dramatically improved to 2.95%.

A blend comprising singly-linked perylene bisimide dimer (di-PBI) acceptor and low band gap polymer P(IID-DTC) donor is utilized to fabricate non-fullerene polymer solar cells. The absorption of P(IID-DTC):di-PBI blend fully covers 400–750 nm of solar spectrum. Dominated bimolecular charge recombination is effectively suppressed by using CH2Cl2 vapor to treat the blend films. The power conversion efficiency of the P(IID-DTC):di-PBI polymer solar cell is finally enhanced to 2.95%.Figure optionsDownload as PowerPoint slide