Optical enhancement of perovskite solar cells by metallic nano-patterns

Abstract

The integration of metallic nanoparticles (MNPs) with plasmonic effects is an alternate approach for managing photons and charge carriers, and is considered a promising method for advancing solar cell technologies. Plasmonic-enhanced solar energy harvesting involves three mechanisms: hot-electron injection, light trapping, and modulation of energy flow direction through dipole-dipole coupling. These phenomena have been observed to significantly enhance the performance of silicon, gallium arsenide, dye-sensitized, and organic solar cells. However, for emerging perovskite solar cells, the light trapping effect, specifically, the far-field scattering via MNPs, has been seldom reported. The anomalous phenomenon is primarily attributed to the size constraints imposed on MNPs by the thickness of the functional layers in cell devices. According to the theory of localized surface plasmon resonance (SPR), the characteristic size of the MNPs needs to be larger than 90 nm to achieve optimal photon scattering. Conversely, charge transport layers like NiO<sub>x</sub> and SnO<sub>2</sub> in perovskite solar cells are typically thin, ranging from a few to several tens of nanometers in thickness. Therefore, the community of perovskite solar cells still faces a great challenge in harvesting light through plasmonic scattering.<br>Compared to MNPs, the shape, size, periodicity, and other characteristic parameters of two-dimensional metal patterns within the horizontal plane are not limited by the thickness of the device's functional layer, thus enabling a more flexible regulation of the SPR response band, vibration intensity, and dissipation method of plasmonic energy. In this study, based on the finite-difference time-domain (FDTD) method and rigorous coupled-wave analysis (RCWA), we systematically investigated the SPR spectra of different metal patterns. The results demonstrate that by optimizing characteristic parameters such as pattern shape, thickness, and periodicity, a significant SPR phenomenon can be observed in the near-infrared region, with scattering dominating over extinction. For the optimal metal ring pattern, the SPR peak corresponds to a wavelength of 772 nm, with relative absorption, scattering, and extinction cross-sections of 0.54, 1.39, and 1.93, respectively. The weighted average absorption of the perovskite response layer in the range of 700-850 nm increased from 53.61% to 65.36%. Correspondingly, the photocurrent density of the device increased from 20.39 to 22.72 mA/cm<sup>2</sup>, and the photoelectric conversion efficiency was relatively improved by 11.45%. This research provides a novel path for light trapping design in perovskite solar cells in the near-infrared region, and serves as a "spectrum-based" reference for SPR regulation in other similar devices.