... coefficient; low band gap; high charge mobility; favorable blend morphology; environmental stability; suitable HOMO/LUMO level and solubility. Solar Cells – New Aspects and Solutions 466 ... properties. Polyfluorene, however, has a band gap of ~3.0eV, which limits its application in Solar Cells – New Aspects and Solutions 478 M Zn(CH2COO) and 0.1 M Na2S aqueous solution for ... Fluorene-based low band-gap copolymers for high performance photovoltaic devices. Applied Physics Letters, Vol.84, No.10, (March 2004), pp. 1653, ISSN 1077- 3118 Solar Cells – New Aspects and Solutions...