Semiconductor plasmon-sensitized broadband upconversion and its enhancement effect on the power conversion efficiency of perovskite solar cells
Photon upconversion (UC) is an attractive strategy to substantially enhance the power conversion efficiency (PCE) of solar cells via upconverting unavailable near-infrared sunlight to available visible light. However, to date, it is almost infeasible to achieve effective PCE improvement of solar cells with the assistance of UC materials, limited by their poor UC efficiency and extremely weak and narrowband near-infrared absorption. Here, we demonstrate the efficient photon energy UC in semiconductor plasmon mCu2−xS@SiO2@Er2O3 (mCSE) nanocomposites, where the broadband semiconductor plasmon (800–1600 nm) of mCu2−xS serves as an antenna to sensitize UC of Er2O3 nanoparticles. The overall upconversion luminescence (UCL) of the composites was dramatically enhanced by a factor of ∼1000, with a maximal inner quantum efficiency of 14.3%. The excitation range was expanded, ranging from 800 to 1600 nm. As a proof-of-concept, the highly efficient mCSE nanocomposites were utilized to improve the PCE of perovskite solar cells (PSCs). The expansion of the near-infrared response (800–1000 nm) and considerable improvement of the PCE were obtained, with an optimum PCE of 17.8%. The mCSE composites in PSCs enhanced the photocurrent via electron transfer from oxygen defects to the conduction band of TiO2 under irradiation of one sunlight. Under irradiation of 15 suns, the electron transfer and reabsorption of UCL both contributed to the enhancement of PCE. Our work can provide an insightful thought on boosting UC efficiency as well as broadening the PCE of PSCs.