Abstract
Ferroelectric functionalized dye-sensitized solar cells were fabricated by using a positively-poled LiNbO3 substrate coated with ITO (ITO-LiNbO3) as a collector electrode and demonstrated enhanced power conversion efficiency. Surface potential properties of TiO2 nanoparticle film coated on the ITO-LiNbO3 (TiO2/ITO-LiNbO3) examined by Kelvin probe force microscopy (KPFM) confirmed that a large electric field (a few 10 V/µm) generated from LiNbO3 can penetrate through the ITO layer and is applied to TiO2 film. This polarization-induced electric field leads to an increased photocurrent density by attracting and promoting electrons to direct transport through the mesoporous TiO2 network toward the collector electrode and a decreased charge recombination by facilitating electrons to pass through fewer boundaries of nanoparticles, resulting in high power conversion efficiency. The power conversion efficiency was enhanced by more than 40% in comparison with that without polarization-induced electric field. Incorporating functional ferroelectrics into photovoltaic cells would be a good strategy in improving photovoltaic performance and is applicable to other types of photovoltaic devices, such as perovskite solar cells.
Highlights
The utilization of solar energy becomes increasingly important, as the fossil and mineral sources are limited and the main sources of environmental pollution
Different with the other organic photovoltaic devices, in the Dye-sensitized solar cells (DSCs) the charge generation is done at the TiO2-dye interface and the charge transport is completed by the TiO2 and the electrolyte
Yuan et al.[17] and Nalwa et al.[18] obtained an enhanced power conversion efficiency (PCE) by introducing a ferroelectric polyvinylidene fluoride (PVDF) layer into polymer solar cells (PSCs), the former demonstrated an increased open-circuit voltage (Voc) resulting from an internal electric field ensured by the ferroelectric polymer layer and the later verified an enhanced photocurrent density (Jsc) and fill factor (FF) owing to enhanced exciton dissociation by the local electric field of ferroelectric dipoles
Summary
The utilization of solar energy becomes increasingly important, as the fossil and mineral sources are limited and the main sources of environmental pollution. It is worth mentioning that, at the interface of ITO-LiNbO3 and nanostructured TiO2 film, the polarization-induced charges will not be fully compensated by the low-concentration free charges in semiconductor, which leads to the formation of an uncompensated internal field in the TiO2 nanoparticles Such a polarization-induced electric field is anticipated to favor charge transport in DSCs. LiNbO3 single crystal is employed for this study because of its advantages in material characteristics such as (1) the possession of a large spontaneous polarization (P) of 75 μC/cm[2] arising from the ionic displacements within the crystal lattice, which is highly stable due to a large coercive field
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