Influence of Sidechain Elongation on Photovoltaic Response of Sidechain-Based Statistical Anthracene-Containing Copolymer

Abstract

A new sidechain-based statistical anthracene-containing poly(arylene-ethynylene)-alt-poly(p-phenylene-vinylene) (P2) bearing 2-ethylhexyloxy and decyloxy side chains was synthesized to study the effect of elongating the sidechain length from octyloxy (as in P1) to decyloxy (as in P2) on the photovoltaic performance. The polymer was prepared using the Horner-Wadsworth-Emmons olefination reaction of two dialdehydes with two bisphosphonate esters. NMR and FTIR spectroscopy characterization were employed to prove the formation of the desired polymeric structure. The photophysical and electrochemical properties showed a broad spectral range of absorption in the visible region and reversible redox activity, respectively. Thermogravimetric analysis (TGA) indicated good thermal stability. Non-optimized bulk-heterojunction solar cells achieved power conversion efficiency (PCE) of 2.4 % for P2. The reduced performance of P2 compared to P1 based solar cells (PCE 3.8%) might originate from inferior nanomorphology of the active layer blend and/or the “dilution” of the photoactive conjugated backbone upon elongation of solubilising sidechains.