Vat Dye Safranin O- and Perylene-Based Conjugated Donor–Acceptor Polyimide as Sensitizer for Dye-Sensitized Solar Cells

Abstract

Nanocrystalline TiO2 and conjugated polyimide are good composite materials for solar energy harvesting applications. Vat dyes have a specific high color fastness property with high wavelength absorption. By applying this property of vat dyes, we synthesized Safranin O and a perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA) based conjugated polyimide through the condensation polymerization technique. Synthesized polyimide was used to construct a TiO2–polymer composite material for dye-sensitized solar cells (DSSCs). The synthesized polyimide has good absorption properties, and a small bandgap of 2.23 eV, contains alternating electronaccepting–electrondonating units, and revealed high thermal stability. It shows good electrical properties, i.e., conductivity of the order of ∼10–4 S cm–1 and an activation energy of 0.1 eV before transition and 0.6 eV after transition, follows an Arrheniustype behavior, and has thermal transitions. Fabrication of electrodes and DSSC was performed for determining the photovoltaic properties of the synthesized polyimide. The obtained photovoltaic parameters, i.e., Jsc = 65 μAcm–2, Voc = 0.128 V, and FF = 0.36, demonstrated their successful use in dye-sensitized solar cells.