Two novel conjugated polymer acceptors (PTO and NTO) were designed and synthesized. PTO and NTO possess alkoxy-substituted thiophene as electron donor moiety and ethynyl moiety as the π-bridge in the conjugated polymer backbone

while perylene diimide (PDI) or naphdiimide (NDI) moiety are used as electron acceptor moiety in their conjugated polymer backbones. Both PTO and NTO exhibited broad light-absorption spectra and low lowest unoccupied molecular orbital energy levels (>—3.80eV). All-polymer solar cells (all-PSCs) were fabricated using these copolymers as electron acceptors and a medium-bandgap conjugated polymer

PBDB-T

as the electron donor. The resulting all-PSCs based on NTO exhibited a power conversion efficiency of 3.7%

which is higher than that of the devices with PTO as acceptor (2. 8%). The performance improvement was attributed to the higher open-circuit voltage

greater charge carrier mobility of the PBDB-T:NTO based devices.