Effect of Metal-Precursor Stacking Order on Volume-Defect Formation in CZTSSe Thin Film: Formation Mechanism of Blisters and Nanopores.

In this study, we investigated the effect of the stacking order of metal precursors on the formation of volume defects, such as blisters and nanopores, in CZTSSe thin-film solar cells. We fabricated CZTSSe thin films using three types of metal-precursor combinations, namely, Zn/Cu/Sn/Mo, Cu/Zn/Sn/Mo, and Sn/Cu/Zn/Mo, and studied the blister formation. The blister-formation mechanism was based on the delamination model, taking into consideration the compressive stress and adhesion properties.

Atomic Layer Deposition of Ultrathin ZnO Films for Hybrid Window Layers for Cu(In,Ga)Se Solar Cells.

The efficiency of thin-film chalcogenide solar cells is dependent on their window layer thickness. However, the application of an ultrathin window layer is difficult because of the limited capability of the deposition process. This paper reports the use of atomic layer deposition (ALD) processes for fabrication of thin window layers for Cu(In,Ga)Se (CIGS) thin-film solar cells, replacing conventional sputtering techniques.

Design of Grating AlO Passivation Structure Optimized for High-Efficiency Cu(In,Ga)Se Solar Cells.

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se (CIGS) solar cells with a grating aluminum oxide (AlO) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. AlO is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL.

CZTSSe Formation Mechanism Using a Cu/Zn/SnS Stacked Precursor: Origin of Triple CZTSSe Layer Formation.

In this study, to control the formation of non-uniformly distributed large voids and Cu-Sn alloy agglomeration, which leads to local compositional misfit and secondary phase formation, a SnS compound precursor was applied instead of metal Sn to avoid compositional non-uniformity. Using a Cu/Zn/SnS stacked precursor, a temperature tracking experiment was conducted to confirm the formation controllability of the void and the secondary phase. According to the results of this temperature-profile tracking experiment, it was confirmed that the large void was successfully controlled; however, an additional ZnSSe secondary phase layer was formed in the middle of the CZTSSe upper layer and small voids were distributed relatively uniformly in the bottom CZTSSe layer.

Enhanced Power Conversion Efficiency of Dye-Sensitized Solar Cells by Band Edge Shift of TiO Photoanode.

By simple soaking titanium dioxide (TiO) films in an aqueous NaS solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage () and the fill factor () was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV-visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the NaS modification led to the formation of anions on the TiO surface, and thereby shifted the conduction band edge of TiO in the negative (upward) direction, inducing an increase of 29 mV in the .

Flexible CuZnSn(S,Se) solar cells with over 10% efficiency and methods of enlarging the cell area.

For kesterite copper zinc tin sulfide/selenide (CZTSSe) solar cells to enter the market, in addition to efficiency improvements, the technological capability to produce flexible and large-area modules with homogeneous properties is necessary. Here, we report a greater than 10% efficiency for a cell area of approximately 0.5 cm and a greater than 8% efficiency for a cell area larger than 2 cm of certified flexible CZTSSe solar cells.

Controlled fabrication of mesoporous TiO 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). TiO 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.

Improved Photovoltaic Properties of Dye-Sensitized Solar Cells with KNO3-Modified Photoelectrodes.

The surface of a TiO2 photoelectrode was modified through a dip-coating process using an aqueous potassium nitrate (KNO3) solution to increase the power-conversion efficiency of dye-sensitized solar cells (DSSCs). The KNO3-modified TiO2 electrode was applied to the photoanode of the DSSCs. The DSSC with the KNO3-modified TiO2 electrode exhibited a short-circuit current (J(sc)) of 15.

Incorporation of Potassium Water Glass on Photoelectrodes and Its Effects on the Performance of Dye-Sensitized Solar Cells.

We applied potassium water glass (PWG) for a modification of photoelectrodes and investigated the effects of this modification on the photovoltaic properties of dye-sensitized solar cells (DSSCs). The PWG-modified TiO2 electrodes were prepared by soaking the TiO2 films in an aqueous PWG solution, and the resulting electrodes were applied to the photoanodes of DSSCs. Compared with a reference device with pristine TiO2 electrode, the power conversion efficiency of a DSSC with a PWG-modified TiO2 electrode was improved by about 26% because of the enhanced short-circuit photocurrent (J(sc)) and open-circuit voltage (V(oc)).

Effect of TiCl4 Post-Treatment on the Embedded-Type TiO2 Nanotubes Dye-Sensitized Solar Cells.

We have studied the effect of TiCl4 post-treatment on the embedded-type TiO2 nanotubes (NT)-dye-sensitized solar cells (DSSCs). The TiO2 nanoparticles layer formed on TiO2 NTs surface by TiCl4 post-treatment showed different morphologies depending on TiCl4 treatment temperature. These different morphologies influenced the cell efficiency of TiO2 NT-DSSCs.

Fabrication of Double-Layered TiO2 Films with Nanosphere Light Scatterers by One-Step Soaking Method.

Nanostructured TiO2 films with a double-layered structure are prepared by a lacile one-step soaking method. We have investigated the morphology of nanostructured TiO2 films according to the reaction time, concentration of the reactant, and reaction temperature of the soaking reaction, which all have a significant effect on the thickness and layered-structure of the nanostructured TiO2 films. The TiO2 films prepared by this soaking method have a unique double-layered structure, which is composed of a dense TiO2 bottom layer and stacked TiO2 nanospheres on the top layer.

Effects of Sodium Dodecyl Sulfate as a Co-Adsorbate on the Performance of Dye-Sensitized Solar Cells.

As a surface modifier, sodium dodecyl sulfate (SDS), was applied to dye-sensitized solar cells (DSSCs), and its effects on the photovoltaic performance of the solar cells were investigated. When the SDS was co-adsorbed with dye (N719) onto TiO2 surface, the DSSCs with SDS showed an increase in short-circuit current (Jsc), open-circuit voltage (Voc) and fill factor, leading to a considerable improvement of over 23% in power conversion efficiency, compared to the reference cell without SDS. Incorporation of SDS on TiO2 surface induced longer lifetime of electrons injected from excited dyes to conduction band of TiO2, leading to an increase in the electron collection efficiency and thus an enhancement in Jsc.

Crystallization Behavior of Solution-Processed CIGSe Thin Film Semiconductor by Stepwise Annealing Process.

CuIn(x)Ga1-xSe2 (CIGS) thin films were prepared by a solution-based CuInGa (CIG) precursor- selenization process. First, we investigated the effect of selenization temperature on the formation of polycrystalline CIGS and grain growth. The CIG precursor films were selenized using a two-step process to investigate the reaction of Se and CIG precursors during the formation of CIGS thin films.

Effect of Sulfurization Temperature on Solution-Processed Cu2ZnSnS4 Thin Films.

Cu2ZnSnS4 (CZTS) solar cells are attracting significant attention as an alternative to CIGS (Culn1-xGa(x)S2) solar cells because of the non-toxic and inexpensive constituent elements of CZTS. Recently, solution-based deposition methods are being developed because they have advantages such as suitability for use in large-area deposition, high-throughput manufacturing, and a very short energy payback time with drastically lower manufacturing costs. In this work, we fabricated solution-based CZTS thin films and investigated them in order to observe the effects of sulfurization temperature on CZTS thin films.

Effects of Ta Addition Through Co-Sputtering on the Electrical Characteristics of Indium Tin Oxide Thin Film Transistors.

We have investigated the effects of adding (Ta) ions to InSnO thin films by co-sputtering on the performance of InSnO thin film transistors (TFTs). TaInSnO TFTs exhibited significantly lower off currents and higher on/off current ratios. Ta ions, owing to their strong affinity to oxygen suppress the formation of free electron carriers in thin films; and hence, play an important role in enhancing the electrical characteristics of the TFTs.

Nanostructured p-type CZTS thin films prepared by a facile solution process for 3D p-n junction solar cells.

Nanoporous p-type semiconductor thin films prepared by a simple solution-based process with appropriate thermal treatment and three-dimensional (3D) p-n junction solar cells fabricated by depositing n-type semiconductor layers onto the nanoporous p-type thin films show considerable photovoltaic performance compared with conventional thin film p-n junction solar cells. Spin-coated p-type Cu2ZnSnS4 (CZTS) thin films prepared using metal chlorides and thiourea show unique nanoporous thin film morphology, which is composed of a cluster of CZTS nanograins of 50-500 nm, and the obvious 3D p-n junction structure is fabricated by the deposition of n-type CdS on the nanoporous CZTS thin films by chemical bath deposition. The photovoltaic properties of 3D p-n junction CZTS solar cells are predominantly affected by the scale of CZTS nanograins, which is easily controlled by the sulfurization temperature of CZTS precursor films.

Enhanced performance of polymer solar cells with a fluorocyanophenyl compound as an additive.

The efficiency of polymer solar cells (PSCs) with P3HT [poly(3-hexyl thiophene)]:PC61BM [[6,6]-phenyl C61-butyric acid methyl ester] blend film was improved by the incorporation of a fluorocyanophenyl compound, 3,4,5,6-tetrafluorophthalonitrile (TFP), as an additive. When the amount of TFTadditive was 5 wt% based on the total amount of P3HT and PC61BM, the highest efficiency was achieved. The annealed PSC with 5 wt% TFP had a power conversion efficiency of 4.

Effect of Ta addition of co-sputtered amorphous tantalum indium zinc oxide thin film transistors with bias stability.

In this work, we have fabricated thin film transistors (TFTs) using amorphous tantalum indium zinc oxide (a-TaInZnO) channels by the co-sputtering process. The effects of incorporating tantalum on the InZnO material were investigated using Hall-effect measurement results, and electrical characteristics. We also found that the carrier densities of thin films and the transistor on-off currents were greatly influenced by the composition of tantalum addition.

Highly reproducible planar Sb₂S₃-sensitized solar cells based on atomic layer deposition.

A high-quality Sb₂S₃ thin-absorber with controllable thickness was reproducibly formed by atomic layer deposition (ALD) technique. Compared with conventional chemical bath deposition (CBD), the Sb₂S₃ absorber deposited by ALD did not contain oxide or oxygen impurities and showed a very uniform thickness of Sb₂S₃ absorbers formed on a rough surface of dense blocking TiO₂/F-doped SnOv (bl-TiO₂/FTO) substrate. The planar ALD-Sb₂S₃ solar cells comprised of Au/Poly-3-hexylthiophene/ALD-Sb₂S₃/bl-TiO₂/FTO showed significantly improved power conversion efficiency of 5.

Light harvest properties of dye-sensitized solar cells with different spatial configurations of reflecting layer.

Dye-sensitized solar cells (DSSCs) were fabricated using an additional porous nanocrystalline titanium oxide reflecting layer in order to improve light harvesting properties. Because of the high reflectance and scattering characters of the nanocrystalline titanium oxide, photocurrent conversion efficiency and short circuit current density of DSSCs were improved. This study reports the relationship between the spatial configuration of the additional reflecting layer and the performance enhancement of DSSCs in order to investigate the optimal condition and the origin of the improved performance because spatial configuration can effect on properties positively or negatively.

Effects of addition of Ta and Y ions to InZnO thin film transistors by sol-gel process.

We have investigated the effects of the addition of tantalum (Ta) and yttrium (Y) ions to InZnO thin film transistors (TFTs) using the sol-gel process. TaInZnO and YInZnO TFTs had significantly lower off current and higher on-to-off current ratio than InZnO TFTs. Ta and Y ions have strong affinity to oxygen and so suppress the formation of free electron carriers in thin films; they play an important role in enhancing the electrical characteristic due to their high oxygen bonding ability.

Investigation of crystallization behavior of CIG-Se bi-layer thin films.

Copper indium gallium diselenide (CIGSe) thin film was fabricated via a thermal treatment of GIG-Se bi-layer thin films. A CIG layer was prepared first, by a chemical solution deposition (CSD) process. The Se layer was deposited separately on the CIG layer by evaporation.

Pixel-isolation walls of liquid crystal display based on prepolymer containing vinyl cinnamate.

Pixel-isolated liquid crystal (PILC) mode investigated in this work is obtained by phase separation induced by the anisotropic photoreaction of a prepolymer containing a vinyl cinnamate monomer. It was found that the incorporation of the cinnamate monomer was an efficient method for the control of the interfacial properties between LC and polymer walls. Polarization-selective photo-curing of the prepolymer containing a cinnamate monomer was closely related with the liquid crystal orientation at the polymer wall boundary resulting in electro-optical performance improvement.

8.01% CuInGaSe2 solar cells fabricated by air-stable low-cost inks.

CuInGaSe(2) (CIGS), a promising thin film solar cell material, has gained lots of attention in decades due to its high energy conversion efficiency and potential lower manufacture cost over conventional Si solar cells. As a cheaper processing method compared to vacuum-based techniques, solution-based deposition has been successfully applied to fabricate electronic devices, such as transistors and solar cells. In this paper, we reported CIGS thin film solar cells with an energy conversion efficiency reaching up to 8.