Enhancement of UV-light harvesting in perovskite solar cells by internal down-conversion with Eu-complex hole transport layer

Abstract

Recently, based on a lot of advantages of organic–inorganic lead halide perovskites, they have been applied in many ways, among which it exhibited outstanding characteristic for photovoltaic performance in application to solar cells. The CH3MH3PbI3 (MAPbI3)-perovskite solar cells (PSCs) show high solar energy conversion efficiency compared to conventional solar cells, but because they are greatly affected by external environments (such as temperature, moisture, light, etc.). For this reason, detailed researches are needed to improve the performances of the perovskite materials and prevent the degradation of the PSCs. Since less than 50% of sunlight contains the visible light and most of its energy can be used, the converting incident light from UV and IR regions into visible light for more productive and efficient solar cells must also be studied as well as the stability improvement. The main purpose of this study is to enhance the availability of UV-light used in the PSCs. Ultimately, we tried to increase the utilization of UV-light in sunlight and consequently improve the performance of the PSCs. Therefore, PSCs to be used were synthesized by controlling amounts of Eu-complex and injecting them into PEDOT:PSS to give a change in the hole transport layers (HTLs). By introducing Eu-complex, a down-conversion material, that absorbs light in UV range and re-emits the light in visible range into PEDOT:PSS, which has a great advantage as HTL with stability against UV-light and generation of more photon increase light-harvesting. As a result, the Eu-complex was shown to enhance the energy conversion efficiency of the PSCs as much as 25% and to raise the light-harvesting of the UV region through the internal down-conversion process.