An overview of technological aspects of Cu(In,Ga)Se 2 solar cell architectures incorporating ZnO nanorod arrays (original) (raw)
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Nanowire dye-sensitized solar cells
Nature materials, 2005
Th e DSC is currently the most effi cient 2 and stable 3 excitonic photocell. Central to this device is a thick nanoparticle fi lm that provides a large surface area for the adsorption of lightharvesting molecules. However, nanoparticle DSCs rely on trap-limited diff usion for electron transport, a slow mechanism that can limit device effi ciency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle fi lm is replaced by a dense array of oriented, crystalline ZnO nanowires. Th e nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fi ft h as large as a nanoparticle cell. Th e direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun effi ciency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
Solar Energy, 2013
Nanostructured ZnO/In 2 S 3 /CuInS 2 superstrate solar cell with all component layers deposited by a low cost chemical spray pyrolysis (CSP) method is characterized. The characteristics of a cell based on a nano-columnar ZnO window layer and a thin film reference prepared by spray are compared. The aim is to determine the dominating non-ideality and the recombination mechanism of these cells in both dark and illuminated conditions and relate the findings to the imperfections in the cell materials. We performed J-V-T (current-voltage-temperature) measurements in dark and under 0.5-100 mW/cm 2 illumination intensities, and admittance spectroscopy, in the temperature range of 100-360 K. We further measured EQE (external quantum efficiency) at room temperature. The solar cell outputs at AM1.5 of the flat reference cell are: V oc = 497 mV, J sc = 6.4 mA/cm 2 , FF = 62%, g = 2%. The use of a nanostructured instead of a flat window layer resulted in short-circuit current density J sc = 12.2 mA/cm 2 and efficiency of g = 3% at the expense of slightly reduced open-circuit voltage V oc = 430-mV and fill factor FF = 58%. Interestingly, the nanostructured cell performs worse than the flat reference at low illumination intensity, as also indicated by illumination dependent shunt conductance. The diode ideality factor of both cells has a significant temperature and illumination dependence. The absorber bandgaps deduced from EQE are 1.5 eV for the flat cell and 1.3 eV for the structured cell. The nanostructured cell shows an increase of light scattering ability accompanied by a less effective charge carrier separation, compared to those of the flat reference cell. The extrapolation of V oc (T) to 0 K yields 740-830 meV and 950-990 meV at varied illumination intensity, for the structured and the flat reference cell respectively, pointing to a non-midgap defect recombination. C-f-T (capacitance-ac frequency-temperature) analysis indicates that the structured cell has a higher concentration of defects and an additional band of defects. This further explains the limited performance enhancement of the structured cell over the flat cell. The illumination dependent cell parameters reveal that copper diffusion from absorber to buffer layer is likely. To eliminate problems associated with Cu diffusion, binary compounds like Sb 2 S 3 or SnS for use as absorber material are considered to further develop the low-cost superstrate type solar cell deposited by the CSP method.
The simple fabrication of nanorods mass production for the dye-sensitized solar cell
MATEC Web of Conferences
ZnO nanorods were successfully synthesized by the plasma torch with the zinc powder as the source of ZnO. Several testing was conducted to examine the results of ZnO nanoparticles among others are X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD). The results of ZnO nanorods diameter vary from 87 nm to 263 nm which can be seen from SEM images and it is length varies from 300 to 1000 nm. It was found from XRD data that a sharp peak occured at 36.253º. It is indicated a good crystal growth and agreed well with the standard data (JCPDF-ICDD card no.: 36-1451). Effects of electrical current variations of plasma torch of 20, 25, and 30 Amperes on the size of ZnO nanorods are indicated from aspect ratio (72.85, 87.42, and 103 nm). The effects of electrical current of plasma torch on the purity of ZnO were about 95.61%, 98.46%, and 96.49% respectively. The performance of the solar cell at the time with the values of Voc, Jsc, FF, and efficiency are 0.466 V, 1.524 mA/cm 2, , 51.95%, and 0.37% respectively. ZnO nanorods were successfully synthesized by the plasma torch with the zinc powder as the source of ZnO.
Nanostructures for Enhancing the Performance of Thin Film Solar Cells
2021 International Conference on Frontiers of Information Technology (FIT)
Thin-film solar cell provides a better way to make solar energy economically viable by reducing the usage of costly active materials. However, thin-film photovoltaic devices can have limited performance due to low absorption coefficient and/or insufficient absorbing material thickness. Thus, removing this bottleneck of low absorption of light resulting in lower solar to electrical conversion efficiency is of utmost importance in achieving a viable solar conversion source for practical usage. One way of addressing this issue is to adopt light-trapping schemes. The mechanism of light trapping is based on utilizing geometric features to reduce back reflection, increase the optical path inside, and modify the optical response of the active medium. Researchers have demonstrated improvement in thin-film solar cell performance by utilizing nanostructures made of dielectrics (e.g., SiO2, TiO2) and plasmonic metals (Au, Ag, Cu, Al). In our proposed design we incorporated plasmonic nanostructures and an enhancement of 38% in amorphous-Silicon, 29% in P3HT: PCBM, and 47% in perovskite-based solar cells achieved.
Plasmon-enhanced ZnO nanorod/Au NPs/Cu2O structure solar cells: Effects and limitations
Korean Journal of Chemical Engineering, 2017
Cu-based compounds can be a good candidate for a low cost solar cell material. In particular, Cu x O (x : 1-2) has a good visible light absorbing bandgap at 1-2 eV. As for using nanostructures in solar cell applications, metal nanoparticle-induced localized plasmon resonance is a promising way to increase light absorbance, which can help improve the efficiency of solar cells. We fabricated ZnO nanorod/Au nanoparticles/Cu 2 O nanostructures to study their solar cell performance. ZnO nanorods and Cu 2 O layer were synthesized by the electrodeposition method. Size-controlled Au nanoparticles were deposited using E-beam evaporator for localized surface plasmon resonance (LSPR) effect. By inserting Au plasmon nanoparticles and annealing Au NPs in solar cells, we could tune the maximum incident photon-to-current efficiency wavelength. However, the potential well formed by Au NP at the ZnO/Cu 2 O junction leads to charge-trapping, based on the constructed electronic band analysis. LSPR-induced hot carrier generation is proposed to promote carrier transport further in the presence of Au NPs.
In this report, dye-sensitized solar cells (DSSCs) with high energy conversion efficiencies were fabricated using TiO 2 nanorods electrospun from a solution mixture of titanium n-propoxide and poly(vinyl acetate) in dimethyl formamide. Investigation of the charge transport characteristics of this unique type of DSSC disclosed that the efficiency of the DSSCs was enhanced by optimizing the nanorod morphology to facilitate charge transport. Our TiO 2 nanorods have an intrinsically higher sensitizer loading capability than conventional TiO 2 nanoparticles and have much slower recombination lifetimes compared to conventional nanoparticles. Long electron lifetime in nanorod electrode contributes to the enhanced effective photocarrier collection as well as the conversion efficiency. The electron transport behavior of nanorod photoelectrodes was further improved by TiCl 4 post-treatment. The post-treatment reduces the pore volume of nanorod photoelectrodes while improving inter-rod connectivity and enhancing electron diffusion. The electron diffusion coefficient of post-treated nanorod was ∼51% higher than that of an untreated one, leading to a charge collection efficiency that was 19% higher at a incident photonflux of 8.1 × 10 16 cm-2 s-1. Finally, the efficiency of nanorod-based DSSCs was optimized at a photoelectrode thickness of 14 µm to achieve 9.52% under masked illumination of simulated solar light, AM 1.5 Global (V oc) 761 mV, J sc) 17.6 mA cm-2 , fill factor) 70.0%).
Vertically-aligned nanostructures of ZnO for excitonic solar cells: a review
Energy Environ. Sci., 2009
Solar energy converts the sunlight into electricity and is one of the most encouraging renewable, CO2-free and low cost alternative energy source to fossil fuels. Among the different photovoltaic devices the third-generation excitonic solar cells (XSCs), which include organic, hybrid and dye-sensitized solar cells, are promising devices for the achievement of the three main criteria that would lead to large scale commercialization: high efficiency, low cost and the possibility to apply simple and scalable fabrication techniques. Abbreviations & Symbols AAO Anodic aluminum oxide ACN Acetonitrile Ag Silver A-HM Autoclave hydrothermal method ALD Atomic layer deposition Ar Argon ATR-FTIR Attenuated total reflectance infrared BHJ Bulk heterojunction CB Conduction band CBD Chemical bath deposition CBE Chemical beam epitaxy CVD Chemical vapor deposition CE Counter electrode CS Core-shell 1.1.2 Renewable Energy at European level: 20% by 2020 At European level different initiatives have been established in order to reduce greenhouse gas emissions and increase renewable energy use. Besides confronting the climate change, there is a growing concern to reduce the dependence of imported energy and secure our energy supply for the future. In 2007, the 27 EU members adopted the target of 20 % use of renewable energy by the year 2020. 8, 9 crystalline silicon to achieve their highest power conversion efficiency, ~20%. The application of different materials than silicon in second generation devices permitted a slight cost reduction. However, the inorganic materials from thin films, second generation, cells (indium, cadmium, gallium…etc.) are not abundant on the planet and toxic. On the other hand, third generation solar cells also reduce the cost of the module preparation due to the application of organic materials that can be less crystalline. 1.2.1 The photovoltaic effect Since the discovery of the photovoltaic effect by Edmund Becquerel in 1839 from a silver coated platinum electrode immersed in electrolyte, other researchers reported materials with the same photovoltaic effect. Some of these materials are selenium with platinum 24, 25 , selenium with gold 26 and copper-copper oxide thin films in lead sulphide and thallium sulphide. All these cells were thin film Schottky barrier devices that present a barrier to current flow. 27 The Schottky barrier is a semiconductor-metal diode system that exhibits an electron or hole barrier. The latter effect is caused by an electric dipole charge 1.3.1 Classification by type of material Excitonic solar cells can be classified by the type of the semiconductor applied: organic or inorganic. The inorganic semiconductors act as ETM due to their electronic properties, some examples of the most used materials are TiO2, ZnO or CdSe among others. Many different organic semiconductors can be applied in XSC such as dyes, polymers, quantum dots or small organic molecules. These organic materials have properties of ETM (such as under illumination corresponds to the difference between the Fermi level of the semiconductor oxide and the redox potential of the electrolyte. Recently, DSCs with solidstate electrolytes have been reported in order to overcome some problems presented with the liquid electrolytes, for example, solvent evaporation or electrode corrosion. The latter cells are known as solid-state dye-sensitized solar cells (ss-DSC) (Figure 1.11b). 16, 54-56 1.3.1.4 Quantum dot solar cells (QDSC) Quantum dots (QD) or also known as quantum wells (QW) are very small particle semiconductors that due to quantum mechanics their band gaps can be easily tunable changing the particle size. This ability to modify their band gap is very attractive for solar cell applications to be applied as light harvesters. 65 The use of different QDs permits to absorb higher-energy and lower-energy photons reducing the heat loss due to carrier relaxation via phonon emission. 66, 67 These PV devices can be prepared in three different configurations: 1.3.2 Classification by type of junction The photovoltaic energy conversion is produced in the solar cell junction, where the charge separation takes place (see section 1.2.4). The latter charge separation process occurs due to the electrostatic force originated when two electronically different materials are in contact. The contact area of these two materials is the solar cell junction. In this section the different types of junctions between semiconductors materials are presented. 1.3.2.1 The p-n junction The p-n junction is the standard model of an inorganic solar cell (ISC). This junction is created when the same semiconductor is doped differently in two separate regions. One region of the latter semiconductor presents a p-type behavior and the other an n-type (Figure 1.15a). 27 The p-type region is rich of free charge carriers (holes) in the valence band, where the n-type region is electron rich. In the case of conventional silicon solar cells can be doped with trivalent atoms such as boron, aluminum or gallium to produce the p-type region and doped with pentavalent atoms such as antimony, arsenic or phosphorous to obtain an n-type region. 71 The p-n junction acts as a selective barrier to charge carrier flow, providing the asymmetry in resistance which is necessary for photovoltaic conversion. The control of the doping process produces large potential barriers which allow large photovoltages. 27 research work can contribute, from the research point of view, to reach these targets. Chapter 2: Presents the synthesis, preparation and characterization of vertically-aligned ZnO nanorods (NR) electrodes by low-temperature hydrothermal method and their application in Dye sensitized solar cells, DSCs. Several synthesis parameters are optimized and the study of the effect of many factors on the DSCs is also included. Chapter 3: This chapter describes a modified hydrothermal synthesis method applying an autoclave reactor that is used to prepare vertically-aligned ZnO nanostructured electrodes. The comparison of the ZnO nanostructures obtained by the low-temperature and the autoclave hydrothermal methods and the application in DSCs is presented in this chapter. Besides, a new ZnO nanostructure, ZnO nanotrees, were obtained and characterized. Chapter 4: The vertically-aligned ZnO nanostructures were covered with a new semiconductor, Indium sulfide, to enhance its properties and increase the power conversion efficiencies of the DSCs. The preparation, characterization of the ZnO/InxSy core-shell structure is presented and applied in DSCs. Chapter 5: All the vertically-aligned ZnO electrodes prepared in chapter 2, 3 and 4 were applied now in polymer solar cells (PSC). The study of the effect of their different morphologies and the polymer blend infiltration within the nanostructures is presented here. Chapter 6: This chapter describes the experimental procedures: materials, synthesis techniques, solar cells preparation and characterization instruments for all the ZnO nanostructures from chapter 2, 3, 4 and 5.
Nanowire-based dye-sensitized solar cells
Applied Physics Letters, 2005
We describe the design and performance of a ZnO nanowire-based dye-sensitized solar cell. ZnO nanowires with a branched structure were employed as the wide-band-gap semiconductor to construct dye-sensitized solar cells which exhibit energy conversion efficiencies of 0.5% with internal quantum efficiencies of 70%. The nanowires provide a direct conduction path for electrons between the point of photogeneration and the conducting substrate and may offer improved electron transport compared to films of sintered nanoparticles. The devices have light harvesting efficiencies under 10%, indicating that current densities and efficiencies can be improved by an order of magnitude by increasing the nanowire surface area.