Physics

Composite material

Catalysis

Exciton

Organic chemistry

Band gap

Chemistry

Materials science

Energy conversion efficiency

Condensed matter physics

Electron donor

Acceptor

Solar cell

Electron acceptor

Optoelectronics

Polymer

Quantum mechanics

Photochemistry

Organic solar cell

Advanced Materials

A record power conversion efficiency (PCE) of over 19% is realized in planar-mixed heterojunction (PMHJ) organic solar cells (OSCs) by adopting the asymmetric selenium substitution strategy in making a pseudosymmetric electron acceptor, BS3TSe-4F. The combined molecular asymmetry with more polarizable selenium substitution increases the dielectric constant of the D18/BS3TSe-4F blend, helping lower the exciton binding energy. On the other hand, dimer packing in BS3TSe-4F is facilitated to enable free charge generation, helping more efficient exciton dissociation and lowering the radiative recombination loss (ΔE2 ) of OSCs. As a result, PMHJ OSCs based on D18/BS3TSe-4F achieve a PCE of 18.48%. By incorporating another mid-bandgap acceptor Y6-O into D18/BS3TSe-4F to form a ternary PMHJ, a higher open-circuit voltage (VOC ) can be achieved to realize an impressive PCE of 19.03%. The findings of using pseudosymmetric electron acceptors in enhancing device efficiency provides an effective way to develop highly efficient acceptor materials for OSCs.

Achieving 19% Power Conversion Efficiency in Planar‐Mixed Heterojunction Organic Solar Cells Using a Pseudosymmetric Electron Acceptor