A New Up-conversion Material of Ho-Yb-Mg Tri-doped TiO and Its Applications to Perovskite Solar Cells.

A new up-conversion nanomaterial of Ho-Yb-Mg tri-doped TiO (UC-Mg-TiO) was designed and synthesized with a sol-gel method. The UC-Mg-TiO presented enhanced up-conversion fluorescence by an addition of Mg. The UC-Mg-TiO was utilized to fabricate perovskite solar cells by forming a thin layer on the electron transfer layer. The results display that the power conversion efficiency of the solar cells based on the electron transfer layer with UC-Mg-TiO is improved to 16.3 from 15.2% for those without UC-Mg-TiO. It is demonstrated that the synthesized UC-Mg-TiO can convert the near-infrared light to visible light that perovskite film can absorb to improve the power conversion efficiency of the devices.