Interface modification by up-conversion material of Ho3+-Yb3+-Li+ tri-doped TiO2 to improve the performance of perovskite solar cells

In this paper, an enhanced up-conversion luminescence material of Ho3+-Yb3+-Li+ tri-doped TiO2 was prepared by optimizing the concentration of Yb3+ and Li+. The up-conversion material was applied to modify the mesoporous layer TiO2 of the perovskite solar cells. Compared with that of solar cells without modification, the power conversion efficiency of the solar cells with Ho3+-Yb3+-Li+ tri-doped TiO2 modification is increased to 16.9% from 15.5%. In order to deeply understand the improvement, a number of investigations were conducted. The research indicates that the open-circuit voltage is added to 1.08 v from 1.06 v could be attributed to the larger energy difference between the conduction bands of up-conversion material of TiO2 and perovskite material. And the enlarged short-circuit current density is due to the faster electron transfer, reduced recombination, and the expansion of light absorption in the near infrared part of sunlight in the device that induced by adding up-conversion luminescence material.