Synergic effects of upconversion nanoparticles NaYbF4:Ho3+ and ZrO2 enhanced the efficiency in hole-conductor-free perovskite solar cells
Extending the spectral absorption of organic–inorganic mixed-cation perovskite solar cells (PSCs) from visible light to the near-infrared (NIR) range minimizes the nonabsorption loss of solar photons. Few studies have focused on the application of high-fluorescence NaYbF4:Ho3+ upconversion nanoparticles (UCNPs) in solar cells. In this study, NaYbF4:Ho3+ UCNPs were successfully prepared using a solvothermal method. We incorporated the NaYbF4:Ho3+ UCNPs into ZrO2 as the scaffold layer for FA0.4MA0.6PbI3 perovskite solar cells. This design enabled the dual-functional effects, that is, the harvesting of NIR light and its conversion to visible light and the reduction of the electron–hole recombination rate. The effect of different amounts of NaYbF4:Ho3+ UCNPs on the device performance was investigated in detail. The best-performance devices based on optimized addition of UCNPs (40 wt%) could achieve a power conversion efficiency as high as 14.32%, an increase of 28.8% compared with conventional ZrO2 nanoparticle-based PSCs (11.12%). The design of the synergetic operation of UCNPs and ZrO2 in the mesoporous structure of PSCs enhanced the photocurrent and photovoltage. The results offered the flexibility for the device architecture and broaden the solar spectral use of UCNP-based devices.