Marked effects of azulenyl vs. naphthyl groups on donor-π-acceptor-π-donor small molecules for organic photovoltaic cells

Abstract Although the unique electronic and optical properties of azulene, the azulene-containing organic photovoltaic (OPV) materials have sporadically reported. Here, eight donor-π-acceptor-π-donor conjugated OPV materials entailing guaiazulene or naphthalene as electron donor unit were synthesized and characterized. The azulenyl and naphthyl groups have significant influences on their molecular properties and photovoltaic performances. Compared to naphthalene derivatives, azulene derivatives exhibit red-shifted and wider absorption spectra. However, naphthalene derivatives exhibit much deeper highest occupied molecular orbital (HOMO) energy levels, higher hole mobility and better film morphology, remarkably resulting in approximately 2–4 times higher photovoltaic efficiencies than azulene derivatives.