Rational Design of High‐Performance Wide‐Bandgap (≈2 eV) Polymer Semiconductors as Electron Donors in Organic Photovoltaics Exhibiting High Open Circuit Voltages (≈1 V)

Systematic optimization of the chemical structure of wide‐bandgap (≈2.0 eV) “donor–acceptor” copolymers consisting of indacenodithiophene or indacenodithieno3,2‐b ]thiophene as the electron‐rich unit and thieno3,4‐c ]pyrrole‐4,6‐dione as the electron‐deficient moiety in terms of alkyl side chain engineering and distance of the electron‐rich and electron‐deficient monomers within the repeat unit of the polymer chain results in high‐performance electron donor materials for organic photovoltaics. Specifically, preliminary results demonstrate extremely high open circuit voltages (V _ocs) of ≈1.0 V, reasonable short circuit current density (J _sc) of around 11 mA cm⁻², and moderate fill factors resulting in efficiencies close to 6%. All the devices are fabricated in an inverted architecture with the photoactive layer processed by doctor blade equipment, showing the compatibility with roll‐to‐roll large‐scale manufacturing processes. From the correlation of the chemical structure—optoelectronic properties—photovoltaic performance, a rational guide toward further optimization of the chemical structure in this family of copolymers, has been achieved.