Tailoring solar energy spectrum for efficient organic/inorganic hybrid solar cells by up-conversion luminescence nanophosphors

Solar light harvesting ability is one of the key properties in organic/inorganic solar cells. One of the most popular organic materials used is poly(3-hexylthiophene) (P3HT), which can make use of solar spectrum in the range 400-600 nm, however, this polymer is incapable of utilizing low energy photons. Herein, we incorporate erbium ion decorated gadolinium oxymolybdate (GMO:Er) nanophosphors (NPs) into mesoporous acceptor film (TiO₂) in an attempt to enhance the light harvest. The nanophosphor can convert the near-infrared solar spectrum to visible region (near 550 nm), in which the energy can be recaptured by P3HT. The results show that the up-conversion proceeds via the two-photon up-conversion mechanism. It is found that after the incorporation of GMO:Er NPs into TiO₂ at 5 wt%, the charge transfer rate was enhanced from 2.79 to 5.83 × 10⁹ s^-1. The device performance of solar cells based on GMO:Er NPs demonstrates a more than 30% improvement compared to their neat TiO₂/P3HT analogue and such enhancement can be ascribed to the broader light harvest together with faster photoexcited charge transfer. This platform can be readily implemented by introducing more demanding energy conversion phosphors and allows for the development of optoelectronic applications with tailored optoelectronic properties.