Quantum chemistry simulations in an undergraduate project: tellurophenes as narrow bandgap semiconductor materials

The convenient graphical user-interfaces now available with advanced simulation software offer a powerful didactic tool for research-led teaching of methods in quantum chemistry and wider applications of quantum mechanics. In the student project work reported here, a homologous series of semiconducting chalcogenophenes (encompassing poly-thiophenes, poly-selenophenes and poly-tellurophenes) with varying polymer chain lengths were simulated in detail using density functional theory (DFT). Following geometry optimization, energy calculations reveal that increasing the length of the polymer chain (N) from a monomer to a hexamer leads to a narrowing and large-N convergence of the bandgap. It is found that hexa-tellurophene has significantly favourable electronic properties as compared to the other analogues, with a greatly enhanced electron affinity (-2.74 eV), and a corresponding bandgap energy of 2.18 eV, giving a superior matching to the solar spectrum.