Preparation of Efficient Organic Solar Cells Based on Terpolymer Donors via a Monomer-Ratio Insensitive Side-Chain Hybridization Strategy

Creating new donor materials is crucial for further advancing organic solar cells. Random terpolymers have been adopted to overcome shortcomings of regular alternating donor-acceptor (D-A) polymers of which the performance is often susceptible to batch-to-batch variations. In general, the properties and performance of efficient D-1-A-D-2-A and D-A(1)-D-A(2) terpolymers are sensitive to the D-1/D-2 or A(1)/A(2) monomer ratios. Side-chain hybridization is a strategy to address this problem. Here, six D-1-A-D-2-A-type random terpolymers comprising D-1 and D-2 monomers with the same pi-conjugated D unit but with different side chains were synthesized. The side chains, containing either fluorine or trialkylsilyl substituents were chosen to provide near-identical optoelectronic properties but provide a tool to create a better-optimized film morphology when blended with a non-fullerene acceptor. This strategy allows improving the device performance to over 18 %, higher than that obtained with the corresponding D-1-A or D-2-A bipolymers (around 17 %). Hence, side-chain hybridization is a promising strategy to design efficient D-1-A-D-2-A terpolymer donors that are insensitive to the D-1/D-2 monomer ratio, which is beneficial for the scaled-up synthesis of high-performance materials.

Automated summary

Creating new donor materials is crucial for advancing organic solar cells. The performance of regular alternating donor-acceptor (D-A) polymers can vary greatly, but this can be overcome by using random terpolymers. The use of side-chain hybridization is a promising strategy to design efficient terpolymers that are insensitive to monomer ratios.