Synthesis, spectroscopic, electrochemical and photophysical properties of high band gap polymers for potential applications in semi-transparent solar cells.

BACKGROUND: The design of new polymers able to filter the electromagnetic spectrum and absorb distinctly in the UV and high-energy part of visible spectrum is crucial for the development of semi-transparent solar cells. Herein, we report on the synthesis and spectroscopic, electrochemical, and photophysical characteristics of three new polymers, namely (i) Poly(triamterene-co-terephthalate), (ii) Poly[triamterene-co- 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-p,p'-disulfonamide], and (iii) Poly(5-hydroxyindole-2-carboxylate) that might show promise as materials for semi-transparent solar cells.

RESULTS: The energy band gap, refractive index, dielectric constant, and optical conductivity of the electron donor polymer, poly(triamterene-co-terephthalate), were determined to be 2.92 eV, 1.56, 2.44 and 2.43 × 104  S cm-1 , respectively. The synthesized electron acceptor polymers showed a relatively high refractive index, dielectric constant, and optical conductivity. The presence of a direct allowed transition was confirmed between intermolecular energy bands of the polymers.

CONCLUSIONS: The polymers showed relatively high energy gap and deep HOMO levels, making them strong absorbers of photons in the UV region and high energy part of the visible region. The synthesized donor and acceptors performed well relative to P3HT and fullerenes due to the close match of the HOMO and LUMO levels. With further development, the polymers could be viable for use as the active layers of semi-transparent solar cells.