Optical Optimization of the TiO2 Mesoporous Layer in Perovskite Solar Cells by the Addition of SiO2 Nanoparticles.

In this work, SiO2 nanoparticles (NPs) were integrated into the mesoporous TiO2 layer of a perovskite solar cell to investigate their effect on cell performance. Different concentrations of SiO2/ethanol have been combined in TiO2/ethanol to prepare pastes for the fabrication of the mesoporous layer with which perovskite solar cells have been fabricated. Addition of SiO2 NPs of 50 and 100 nm sizes produces an enhancement of cell performance mainly because of an improvement of the photocurrent. This increment is in good agreement with the theoretical predictions based on light scattering induced by dielectric SiO2 NPs. The samples using modified scaffolds with NPs also present a significant lower current-potential hysteresis indicating that NP incorporation also affects the ion accumulation at the perovskite interface, providing an additional beneficial effect. The results stress the importance of the appropriated management of the optical properties on further optimization of perovskite solar cell technology.

Inorganic Surface Engineering to Enhance Perovskite Solar Cell Efficiency.

The photoconversion efficiency of perovskite solar cells (PSCs) is enhanced by the deposition of inorganic nanoparticles (NPs) at the interface between the compact TiO2 electron-selective contact and the mesoporous TiO2 film. The NPs used are core/shell Au@SiO2, where a thin SiO2 coating protects the Au core from the direct chemical interaction with CH3NH3PbI3 halide perovskite used as light-harvesting material. The samples prepared with Au@SiO2 NPs exhibit a higher external quantum efficiency in the complete wavelength range at which perovskite presents light absorption and not just at the wavelengths at which Au@SiO2 NPs present their absorption peak. This fact rules out a direct plasmonic process as responsible for the enhancement of cell performance. A detailed characterization by photoluminescence, impedance spectroscopy, and open-circuit voltage decay unveils a modification of the interfacial properties with an augmentation of the interfacial electrostatic potential that increases both photovoltage and photocurrent. This article highlights the dramatic role of interfaces in the performance of PSCs. The use of reduced quantities of highly stable inorganic compounds to modify the PSC interface instead of the extensively used organic compounds opens the door to a new surface engineering based on inorganic compounds.