Enhanced upconversion red light emission of TiO₂:Yb,Er thin film via Mn doping

TiO₂:Yb,Er films with different concentrations of Mn²⁺ are grown on SiO₂ glass substrates by pulsed laser deposition. It is found that the introduction of Mn²⁺ enhanced the intensity of upconversion emission. In particular, TiO₂:Yb,Er thin film with 5% Mn²⁺ ions exhibits the brightest upconversion emission. The upconversion red emission intensity is increased by 2.5-fold than that of a TiO₂:Yb,Er thin film without Mn²⁺ ions, which is ascribed to the multi-photon absorption and efficient exchange-energy transfer process between Er³⁺ and Mn²⁺. The high transmittance and good conductivity of the films made them possible to act as electron transport layer in solar cells.