Wen Pin Liao

Morphology and Interfacial Energetics Controls for Hierarchical Anatase/Rutile TiO2 Nanostructured Array for Efficient Photoelectrochemical Water Splitting

In this work, a three-dimensional (3D) hierarchical TiO2 nanostructured array is constructed on the basis of the considerations of morphology and interfacial energetics for photoelectrochemical water splitting. The photoelectrode is composed of a core-shell structure where the core portion is a rutile TiO2 nanodendrite (ND) array and the shell portion is rutile and anatase TiO2 nanoparticles (NPs) sequentially located on the surface. The TiO2 ND array provides a fast electron transport pathway due to its quasi-single-crystalline structure. The 3D configuration with NPs in the shell portion provides a larger surface area for more efficient photocharge separation without significantly sacrificing the electron collection efficiency. Moreover, anatase TiO2 NPs constructed on the surface of the ND/rutile TiO2 NP nanostructured array enhance charge separation and suppress charge recombination at the interfacial region due to the higher conduction band edge of anatase TiO2 compared to that of rutile TiO2. A photocurrent density and photoconversion efficiency of 2.08 mA cm(-2) at 1.23 V vs reversible hydrogen electrode (RHE) and 1.13% at 0.51 V vs RHE are, respectively, attained using the hierarchical TiO2 nanostructured array photoelectrochemical cell under illumination of AM 1.5G (100 mW cm(-2)).

Construction of nanocrystalline film on nanowire array via swelling electrospun polyvinylpyrrolidone-hosted nanofibers for use in dye-sensitized solar cells

A 74% enrichment of the efficiency of ZnO nanowire (NW) dye-sensitized solar cells (DSSCs) is achieved by the addition of a novel light-scattering nanocrystalline film (nanofilm). The 100 nm thick nanofilm is derived from the polyvinylpyrrolidone-hosted SnO(2)/ZnO nanofibers electrospun on the top of ZnO NW arrays via methanol vapor treatment followed by high-temperature calcination. Structural characterizations show that the film is composed of SnO(2) and ZnO nanocrystals with a diameter of ∼10 nm. Short-circuit current, open-circuit voltage, and fill factor of the nanofilm/ZnO NW DSSCs are all superior to those of the ZnO NW DSSCs. The mechanism of photocurrent enhancement in the nanofilm/ZnO NW DSSCs has been investigated using optical modulation spectroscopy. Intensity modulation photocurrent spectroscopy (IMPS) measurements reveal that the dye-sensitized nanofilm does not contribute significant photocurrent in the nanofilm/ZnO NW DSSCs. The significant enhancement of the efficiency of the ZnO NW DSSCs is achieved by reflecting unabsorbed photons back into the NW anode using the novel light-scattering layer of nanofilm.

Nanophotonic perovskite solar cell architecture with a three-dimensional TiO2 nanodendrite scaffold for light trapping and electron collection

Nanophotonic perovskite solar cells have been fabricated by infiltrating methylammonium lead iodide (MAPbI3) into the interstices of the quasi-single-crystalline TiO2 nanodendrite (ND) array. The TiO2 ND array in the active layer serves as not only the nanophotonic light trapping structure but also the electron transport medium for enhancing both light harvesting and electron collection to challenge the issue of short electron diffusion length in MAPbI3-based solar cells. Finite difference time domain simulation results indicate that the ND in the MAPbI3 matrix exhibits superior light trapping performance compared to the nanorod (NR), which can well explain the comparable light harvesting in the MAPbI3–TiO2 ND and the MAPbI3–TiO2 NR solar cells although the MAPbI3 amount in the former is ∼10% less. Moreover, the branches developed from the trunks of the NDs will extract the photoelectrons from MAPbI3 to reduce the electron transport length in the MAPbI3 matrix. The higher internal quantum efficiencies, especially at longer wavelengths, confirm the enhanced electron collection in the MAPbI3–TiO2 ND solar cell. Compared to the MAPbI3–TiO2 NR solar cell, the 22% and 25% enhancements in the average Jsc and PCE are respectively attained in the MAPbI3–TiO2 ND solar cells.

Synergistic Effect of Dual Interfacial Modifications with Room-Temperature-Grown Epitaxial ZnO and Adsorbed Indoline Dye for ZnO Nanorod Array/P3HT Hybrid Solar Cell

ZnO nanorod (NR)/poly(3-hexylthiophene) (P3HT) hybrid solar cells with interfacial modifications are investigated in this work. The ZnO NR arrays are modified with room-temperature (RT)-grown epitaxial ZnO shells or/and D149 dye molecules prior to the P3HT infiltration. A synergistic effect of the dual modifications on the efficiency of the ZnO NR/P3HT solar cell is observed. The open-circuit voltage and fill factor are considerable improved through the RT-grown ZnO and D149 modifications in sequence on the ZnO NR array, which brings about a 2-fold enhancement of the efficiency of the ZnO NR/P3HT solar cell. We suggested that the more suitable surface of RT-grown ZnO for D149 adsorption, the chemical compatibility of D149 and P3HT, and the elevated conduction band edge of the RT-grown ZnO/D149-modified ZnO NR array construct the superior interfacial morphology and energetics in the RT-grown ZnO/D149-modified ZnO NR/P3HT hybrid solar cell, resulting in the synergistic effect on the cell efficiency. An efficiency of 1.16% is obtained in the RT-grown ZnO/D149-modified ZnO NR/P3HT solar cell.

P3HT-based nanoarchitectural Fano solar cells.

The finite difference time domain simulation shows the existence of an asymmetric quadrupole of Fano resonance on the surface of a gold-silica core-shell (Au@silica) nanoparticle (NP) as being incorporated into the metal oxide nanoarchitecture/P3HT hybrid. Compared to the metal oxide nanoarchitecture/P3HT hybrid solar cell, a 30% enrichment of the short-circuit current density (Jsc) is attained in the P3HT-based nanoarchitectural Fano solar cell with the Au@silica NPs. The enhancement of charge separation in the cell by the electric field of the Fano resonance is directly evidenced by time-resolved photoluminescence measurements. The increase of the degree of P3HT order in the hybrid by the incorporation of Au@silica NPs into the hybrid active layer may also contribute to the enhancement in the Jsc. Charge carrier dynamic measurements show that an electron collection efficiency of ∼97% can be maintained in the P3HT-based nanoarchitectural Fano solar cell. Significant improvement of the efficiency of the inverted metal oxide/P3HT hybrid solar cell is therefore achieved.

Nanowire dye-sensitized solar cell with a novel light-scattering layer

A significant enrichment of the efficiency of ZnO nanowire (NW) dye-sensitized solar cell (DSSC) is achieved using a novel light-scattering layer of nanofilm. The nanofilm is derived from the polyvinylpyrrolidone (PVP)-hosted SnO2/ZnO nanofibers electrospun on the top of ZnO NW array. To construct a nanofilm on ZnO NW array, the PVP-hosted nanofibers are swollen using methanol vapor followed by a high-temperature calcination. Jsc and Voc of the nanofilm/ZnO NW DSSC are all enhanced compared to those of the ZnO NW DSSC, resulting in a considerable enhancement of the efficiency.