Synthesis of Poly(fluorene-alt-thieno[3,4-b]thiophene) for Photovoltaic Devices

Abstract

Polymer-based bulk heterojunction solar cells have been fabricated using blended films composed of an electron-donating conjugated polymer and an electron-accepting material such as a fullerene derivative; they are promising low-cost, flexible renewable energy sources.1-4 A solar cell’s power conversion efficiency (PCE) is the product of the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) divided by the incident light power density. The Voc of polymer solar cells is generally propor-tional to the energy difference between the highest occupied molecular orbital (HOMO) of the electron donor and the lowest unoccupied molecular orbital (LUMO) of the elec-tron acceptor, suggesting that polymers with deep HOMO levels are advantageous if conditions are otherwise similar. Photovoltaic cells have had PCEs of ca. 5 % reported whe