Enhanced Power Conversion Efficiency of Perovskite Solar Cells with an Up-Conversion Material of Er 3+ -Yb 3+ -Li + Tri-doped TiO 2 .

In this paper, Er3+ -Yb3+ -Li+ tri-doped TiO2 (UC-TiO2 ) was prepared by an addition of Li+ to Er3+ -Yb3+ co-doped TiO2 . The UC-TiO2 presented an enhanced up-conversion emission compared with Er3+ -Yb3+ co-doped TiO2 . The UC-TiO2 was applied to the perovskite solar cells. The power conversion efficiency (PCE) of the solar cells without UC-TiO2 was 14.0%, while the PCE of the solar cells with UC-TiO2 was increased to 16.5%, which presented an increase of 19%. The results suggested that UC-TiO2 is an effective up-conversion material. And this study provided a route to expand the spectral absorption of perovskite solar cells from visible light to near-infrared using up-conversion materials.