Development and Structure/Property Relationship of New Electron Accepting Polymers Based on Thieno[2′,3′:4,5]pyrido[2,3-g]thieno[3,2-c]quinoline-4,10-dione for All-Polymer Solar Cells

Abstract

Several electron accepting polymers having weak accepting-strong accepting (WA-SA) and strong accepting-strong accepting (SA-SA) monomer alternation were synthesized for studies of structure/property relationship in all-polymer solar cells. Two kinds of cyclic amide monomers, 4,10-bis(2-butyloctyl)-thieno[2′,3′:5,6]pyrido[3,4-g]thieno-[3,2-c]isoquinoline-5,11-dione (TPTI) and 5,11-bis(2-butyloctyl)-thieno[2′,3′:4,5]pyrido[2,3-g]thieno[3,2-c]quinoline-4,10-dione (TPTQ), were synthesized as weak accepting monomers (WA). Difluorinated TPTQ (FTPTQ) and well-known perylene diimide (PDI) monomers were synthesized as strong electron accepting monomers (SA). By using 1-chloronaphthalene (CN) as a cosolvent, the morphology of the polymer blended films can be finely tuned to achieve better ordering toward face-on mode and favorable phase separation between electron donor and acceptor, resulting in significant enhancement of short circuit current (J<inf>sc</inf>) and fill factor (FF). The fluorination in the TPTQ unit reduced the dipole moment of the D-A complex and gave a negative effect on a polymer system. PFP showed worse electron accepting property with lower electron mobility than PQP. It is reasoned that the internal polarization plays an important role in the design of electron accepting polymers. As a result, PQP having TPTQ monomer exhibited the best photovoltaic performance with power conversion efficiency (PCE) of 3.52% (V<inf>oc</inf> = 0.71 V, J<inf>sc</inf> = 8.57 mA/cm2, FF = 0.58) at a weight ratio of PTB7-Th:PQP = 1:1, under AM 1.5G. © 2015 American Chemical Society.