Efficiency enhancement in solid dye-sensitized solar cell by three-dimensional photonic crystal

Dye-sensitized solar cells (DSSCs) offer an attractive alternative to conventional solar cells because of their lower production cost. However, the liquid electrolyte used in these cells is unstable because of solvent leakage or evaporation, and DSSCs that use a solid electrolyte do not perform as well. In this paper, we present a design in which a nanocrystal (nc)-TiO2 underlayer is integrated with an optically active porous three dimensional photonic crystals (3D PCs) overlayer, and a sequential infiltration process is adopted to introduce additives to the solid electrolyte. This architecture allows effective dye sensitization, electrolyte infiltration, and charge collection from both the nc-TiO2 and the PC layers, yielding enhanced absorption in a specific spectral region. We describe the fabrication process and demonstrate the improved performance of the fabricated DSSCs, which exhibited conversion efficiencies that were as much as 32% higher than those of a conventional DSSC. This approach should be useful in solid-state devices where pore infiltration is a limiting factor, as well as in weakly absorbing photovoltaic devices. © 2013 The Royal Society of Chemistry.FALS

Controlled fabrication of mesoporous TiO2 hierarchical structures as scattering layers to enhance the power conversion efficiency of dye-sensitized solar cells

To meet the nanofabrication requirements, such as control of structure and scalability, we investigated an electrospray-based method to manufacture scattering layers (SLs) for dye-sensitized solar cells (DSSCs). TiO2 spherical and disk-shaped particles with a large surface area, high crystallinity, uniform nanostructure and good light scattering properties were fabricated via a simple electrospray method. We showed how the morphology and structure of the resulting films can be controlled by varying the droplet evaporation rates before impact on the substrate. Thus, by tuning the process conditions, high-quality TiO2 spheres and disks were obtained. Then, these mesoporous TiO2 particles were used as the SLs in photoelectrodes, which resulted in enhanced power conversion efficiency (PCE). Compared with conventional SLs (8.45%), DSSCs based on spherical and disk-shaped particle SLs yield higher PCEs of 9.0% and 9.53%, respectively. This is because the generated TiO2 spheres and disks provide a large surface area and exhibit excellent light scattering capabilities, allowing a low total internal resistance and a long electron lifetime. © the Owner Societies 2016.

High-quality nonpolar ZnO thin films grown on r-plane sapphire by radio frequency-magnetron sputtering

Nonpolar, a-plane(112̄0)ZnO thin films were epitaxially grown on r-plane(11̄02)sapphire substrate by radio frequency magnetron sputtering. The influence of oxygen partial pressure was studied. With increasing O 2 partial pressure of the Ar/O2 sputtering gas, the ridge-like facet structure of the ZnO film altered to a smooth film. Full width half maximum of X-ray rocking curves for the on-axis(112̄0)reflections were 0.45°, 0.36°, 0.09° and 0.25° for samples grown at Ar/O 2 ratios of 2/1, 1/1, 1/2 and 1/3, respectively. A smooth surface could be obtained under oxygen rich conditions (Ar/O2 ratio: 1/2), enhancing the lateral growth along the c-axis direction. © 2013 Elsevier B.V.FALS

Effect of embedded chalcogenide quantum dots in PbBr2 film on CsPbBr3 inorganic perovskite solar cells

Inorganic perovskite solar cells (PSCs) are considered prospective alternatives to organic PSCs due to their efficiency and relative stability. Cesium lead bromide (CsPbBr3) has a complete perovskite structure, is phase stable, exhibits a wide bandgap energy of 2.3 eV under operating conditions, and is regarded as a suitable material not only for stable PSCs, but also for semi-transparent PSCs. In this study, we synthesize Cu–Zn–In–S–Se (CZISSe) quantum dots (QDs) and demonstrate their novel use for improving the performance of PSC devices. QDs are embedded through ligand-exchange, which replaces long organic chains with thiosulfate (–S2O3) ligands and disperses the S2O3-capped QDs in the PbBr2 solution to prepare QD-blended precursor inks. The QDs promote the crystallization of CsPbBr3 and hole extraction from the photoactive layer. As a result, the optimized power conversion efficiency (PCE) of the QD-incorporated PSC is 5.37%, which is a 22.6% enhancement compared to those of the control devices. This work provides an effective and simple process for enhancing the performance of CsPbBr3-based PSCs. © 2020 The Korean Society of Industrial and Engineering ChemistryFALS

Efficiency enhancement of bifacial Cu2ZnSnSe4 thin-film solar cells on indium tin oxide glass substrates by suppressing In-Sn diffusion with Mo interlayer

We fabricate bifacial Cu2ZnSnSe4 (CZTSe) thin-film solar cells on indium tin oxide (ITO) substrates using a vacuum procedure. We find that, as the annealing temperature increases from 500 to 540 °C, the performance of the CZTSe solar cell rapidly degrades due to Sn–In diffusion. We implement Mo interlayers at the CZTSe absorber/ITO interface to suppress this Sn–In movement. During annealing, the selenized Mo interlayer with MoSe2 effectively acts as a barrier layer to reduce the In diffusion into the CZTSe absorber. The relationship between the Mo thickness and the CZTSe performance is addressed. Because the Mo interlayer is used, the conversion efficiency of the CZTSe solar cells greatly improves, from 0.40% to 5.21% under front illumination. Also, the effects of the bifacial conditions and Mo interlayer thickness on the performance of the CZTSe solar cells are investigated. Under bifacial illumination (front: 1.0 sun/rear: 0.3 sun), the conversion efficiency of the CZTSe solar cells increases by up to 10% compared with that under front illumination only, achieving a value of 5.71% for CZTSe/ITO. © 2018 Elsevier B.V.1

Optimum Substrate Temperature in One-stage Co-evaporation of Cu(ln,Ga)Se-2 Thin Films for High-efficiency Solar Cells

One-stage co-evaporation of Cu(In,Ga)Se2 (CIGS) thin films has strong potential for wide adoption in industry because of its simplicity compared with multiple-stage processes. This study investigated the effects of substrate temperature during CIGS film growth on the efficiency of the resulting ITO/ZnO/CdS/CIGS/Mo structures. CIGS thin films were grown by using one-stage co-evaporation at substrate temperatures ranging from 525 to 550 °C. The device with a CIGS film grown at 535 °C was found to have the highest cell efficiency. In the XRD patterns, films grown at this substrate temperature had the largest texture coefficient for the (220) plane and the smallest full width at half maximum for both the (112) and the (220) planes. Other cell electrical characteristics were also largest for this substrate temperature. Thus, we conclude that the optimal morphological characteristics of CIGS thin films grown at a temperature of 535 °C are responsible for the high efficiency.FALS

Fabrication of Sb2S3 Hybrid Solar Cells Based on Embedded Photoelectrodes of Ag Nanowires-Au Nanoparticles Composite

The Ag nanowire (NW) + Au nanoparticle (NP)-embedded TiO2 photoelectrodes were adopted for conventional planar TiO2-based Sb2S3 hybrid solar cells to improve the cell efficiency. Compared to conventional planar TiO2-based Sb2S3 hybrid solar cells, the Ag NW + Au NP/TiO2-based Sb2S3 hybrid solar cells exhibited an improvement of approximately 40% in the cell efficiency due to the significant increase in both J(sc) and V-oc. These enhanced J(sc) and V-oc were attributed to the increased surface area, charge-collection efficiency, and light absorption by embedding the Ag NWs + Au NPs composite. The Ag NW + Au NP/TiO2-based Sb2S3 hybrid solar cells showed the highest efficiency of 2.17%, demonstrating that the Ag NW + Au NP-embedded TiO2 photoelectrode was a suitable photoelectrode structure to improve the power conversion efficiency in the Sb2S3 hybrid solar cells.1

Effect of Ag Nanowire/ZnO Core Shell Photoelectrodes in Sb2S3-Based Hybrid Solar Cells

We adopted Ag nanowire (NW)/ZnO core–shell photoelectrodes for conventional planar ZnO-based Sb2S3 hybrid solar cells to improve the cell efficiency. The core–shell structure consisted of a network of Ag NWs as the core and a ZnO shell in the form of a coating layer covering the surface of the Ag NWs Compared to conventional planar ZnO-based Sb2S3 hybrid solar cells, the Ag NW/ZnO-based Sb2S3 hybrid solar cells showed an approximately 50% improvement in the power conversion efficiency due to the significant increase in the Jsc In turn, the improved Jsc was attributed to the increased surface area and charge-collection efficiency by the Ag NW network core. Out of several shell thicknesses, a 60 nm thick ZnO shell layer led to cells with the highest efficiency of 3.02%, demonstrating that the Ag NW/ZnO core–shell photoelectrodes effectively improved the efficiency of the Sb2S3 hybrid solar cells. Copyright © 2017 American Scientific Publishers All rights reserved.1

Effects of Thickness of Electrosprayed Spherical TiO2 Photoelectrodes on the Performance of Dye-Sensitized Solar Cells

In a dye-sensitized solar cell (DSSC) consist of a TiO2 nanostructured photoelectrode, the other components are the electrolyte and the counter electrode. Dye molecules adsorbed onto the surface of the TiO2 photoelectrode provide electrons; thus, the photoelectrode determines the performance of the cell. TiO2 photoelectrodes for DSSCs can be fabricated using a number of techniques. Among the various techniques available, the electrospraying method has numerous advantages in that it uses a purely electric field to form the aggregate structure, allowing for independent control of the aggregation, size, and crystallinity of primary nanoparticles. In this study, we investigated the performances of DSSC photoelectrodes consisting of spherical TiO2 nanoparticles. The photoelectrodes were fabricated from a dispersion of TiO2 nanocrystals in ethyl alcohol by using the electrosprayin method, in which different amounts of the TiO2 dispersion were sprayed directly onto fluorine-doped tin oxide substrates. The highest energy conversion efficiency, which was 7.65% under light at AM1.5G, was obtained using a TiO2 electrode with a thickness of 9.5 μm. This was attributable to the high diffuse reflectance of the photoelectrode and the long lifetime of electrons in it. © 2016 by American Scientific Publishers.