Thesis (M.S.)--University of Toledo, 2009. / Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science degree in Chemistry." "A thesis entitled"--at head of title. Bibliography: leaves 75-77.

MINP solar cells ; Hoi Chi-sam. / Includes bibliographical references / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

by Poon Ming-cheong. / Bibliography: leaves 97-102 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

The goal of renewable solar energy research is to develop low-cost, high-efficiency photovoltaic technologies. However, with the growing deployment of solar cells, approaching the terawatt scale, absorber materials reliant upon rare or unfriendly elements become a crucial issue. Thus, the primary objective of this dissertation is the development of a low-cost fabrication method for (i) thin-film solar cells and (ii) dye-sensitized solar cells using earth-abundant materials. In thin-film solar cells, the kesterite Cu₂ZnSnS₄ with earth abundant elements is used as an absorber layer. It possesses a high absorption coefficient, direct band gap, and good long-term stability compared to the traditional CdTe and Cu(In,Ga)(S,Se)₂ (CIGS) absorber layers. A facile hot-injection approach for synthesizing Cu₂ZnSn(S,Se)₄ nanocrystals with varied Se to (S+Se) ratio is developed to systematically investigate the role of Se in Cu₂ZnSn(S,Se)₄ nanocrystals and the evolution of Cu₂ZnSn(S,Se)₄ nanocrystals to Cu₂ZnSn(S,Se)₄ film during the sulfurization step to address the problems associated with its narrow compositional window and the loss of Sn during heat treatment. Additionally, the existing substrate-type device configuration for these solar cells uses a molybdenum (Mo) back contact, which suffers from serious disadvantages like the (i) presence of a Schottky barrier at the Mo/Cu₂ZnSn(S,Se)₄ interface and (ii) decomposition of Cu₂ZnSn(S,Se)₄ at the Mo interface. Accordingly, a low-cost and Mo-free superstrate-type device configuration of Au/Cu₂ZnSn(S,Se)₄/CdS/TiO₂/ITO/glass is developed to evaluate the conversion efficiency and to avoid the occurrence of a Schottky barrier at the interface and potential decomposition pathways induced by the formation of Mo(S,Se)₂. Furthermore, with the addition of ethyl cellulose, the loss of Sn associated with the conversion of CZTSe to CZTSSe during the grain growth process is mitigated, leading to an increase in the conversion efficiency compared to that of the precursor film without using ethyl cellulose. Such an improvement can provide insight into the grain growth of CZTSSe during the sulfurization process and thereby enhance the feasibility of sustainable, high efficiency CZTSSe solar devices. The excellent characteristics of dye-sensitized solar cells (DSSCs) with short energy-payback time, simple assembly, and eco-friendly features make them a potential option to utilize solar energy. Accordingly, a facile, low-cost, template-free route for TiO₂ hollow submicrospheres embedded with SnO₂ nanobeans is developed for use as a versatile scattering layer in DSSCs. Our designed structure simultaneously promotes dye adsorption, light harvesting, and electron transport, leading to a 28 % improvement in the conversion efficiency as compared with the film-based SnO₂. In addition, a naturally-derived carbonaceous material as a Pt-free counter electrode for DSSCs is also developed for the first time: carbonized sucrose-coated eggshell membrane (CSEM). It is found that the carbonized sucrose-coated eggshell membranes consist of unique micropores of less than 2 nm, which effectively catalyze the triiodide into iodide in the light-electricity conversion process, leading to an improvement in the V [subscript oc] and a competitive efficiency as compared to that of a DSSC with a traditional Pt-based counter electrode. / text

Thesis (Ph. D.)--Johns Hopkins University, 2004. / Includes bibliographical references.

The aim of this thesis was to undertake a comprehensive research to study the broadband light absorption enhancement in organic solar cells (OSCs) with different nano-structures, thereby improving short-circuit current density and efficiency. Absorption enhancement in OSCs having different photonic structures, compared to the control planar cell configuration, was analyzed and studied using the optical admittance analysis and finite-difference time-domain (FDTD) method. After a brief overview of the latest progresses made in OSCs, the basic optical principles of light scattering, surface plasmon polaritons (SPPs), localized surface plasmon resonance (LSPR), diffraction effect and waveguide mode, that had been employed for light trapping in OSCs, are discussed. Optical admittance analysis reveals that light absorption in inverted OSCs, based on polymer blend layer of P3HT:PCBM, is always greater than the conventional geometry OSCs fabricated using an ITO/PEDOT:PSS anode. The inverted bulk heterojunction OSCs, made with a pair of an ultrathin Al-modified ITO front cathode and a bi-layer MoO3/Ag anode, exhibited a superior power conversion efficiency (PCE) of 4.16%, which is about 13% more efficient than a control normal OSC. It is shown that the reverse configuration allows improving charge collection at cathode/blend interface and also possessing a dawdling degradation behavior as compared to a control regular OSC in the accelerated aging test. Light absorption enhancement in ZnPc:C60-based OSCs, made with substrates having different structures, for example, surface-modified Ag nanoparticles and 1-D photonic structures, was analyzed. The effect of an ultra-thin plasma-polymerized fluorocarbon film (CFx)-modified Ag nanoparticles ii (NPs)/ITO anode on the performance of OSCs was optimized through theoretical simulation and experimental optimization. This work yielded a promising PCE of 3.5 ± 0.1%, notably higher than that with a bare ITO anode (2.7±0.1%). The work was extended to study the performance of OSCs made with CFx-modified Ag NPs/ITO/polyethylene terephthalate (PET) substrate. The resulting flexible OSCs had a relatively high PCE of 3.1±0.1%, comparable to that of structurally identical OSCs fabricated on ITO-coated glass substrate (PCE of 3.5±0.1%). The distribution of the sizes of the Ag NPs, formed by the thermal evaporation, was over the range from 2.0 nm to 10 nm. The results reveal that the localized surface plasmon resonance, contributing to the broadband light absorption enhancement in the organic photoactive layer, was strongly influenced by the size of Ag NPs and the dielectric constant of the surrounding medium. A new OSC structure incorporating a transparent PMMA/ITO double layer grating electrode was also developed. 1-D PMMA/ITO double layer grating, fabricated using nano-imprinting and low processing temperature ITO sputtering method, has a period of 500 nm. Light absorption in grating OSCs under TM, TE and TM/TE hybrid polarizations was calculated using FDTD simulation in the wavelength range from 400 nm to 800 nm. We profiled the electric field distribution and analyzed the structural requirement for confining the waveguide modes in the organic photoactive layer. The effects of the periodicity and the pitch size on light scattering, simultaneous excitation of horizontally propagating SPPs, LSPR and the waveguide modes for light harvesting in grating OSCs were analyzed. The efficiency enhancement in the grating OSCs (PCE 3.29%) over the planar control device (PCE 2.86%) is primarily due to the increase in the short-circuit current density from 11.93 mA/cm2 to 13.57 mA/cm2 (13.7% enhancement). The theoretical results agree with the experimental findings in showing that the improved performance in grating OSCs is attributed to the absorption enhancement in the active layer

As fossil fuels, the major source of energy used today, create the greenhouse gas carbon dioxide which causes global warming, alternative energy sources are necessary in the future. There is a need for different types of renewable energy sources such as hydropower, windpower, wave- power and photovoltaics since different parts of the world have different possibilities. The sun is a never ending energy source. Photovoltaics use the energy of the sun and converts it into electricity. There are different types of photovoltaics and a combination of them could provide humankind with energy in a sustainable way. In this thesis dye-sensitized solar cells are investigated. Materials for the counter electrode have been investigated and resulting in a polymer based cathode outperforming the traditionally used platinized counter electrode in a cobalt-based redox mediator system (paper I). The sensitizer of the TiO2 was investigated, in this study by modifications of the π-linker unit in an organic donor-linker-acceptor based dye. Four new dyes were synthesized, all four showing extended absorption spectra compared to the reference dye. However, it was found that increasing the absorption spectrum does not neces- sarily increase the power conversion efficiency of the solar cell (paper II). In the last part of this thesis, water-based electrolyte dye-sensitized solar cells were investigated. A hydrophilic dye with glycolic chains close to the center of regeneration was synthesized. The results show increased wettability by water-based electrolyte for the sensitized surface, increased regenera- tion and performance for the hydrophilic dye compared to a hydrophobic dye (paper III). The glycolic chains complex with small cations such as Na+ and K+ in the electrolyte, this proba- bly facilitate the regeneration of the hydrophilic dye even further (paper IV). In this thesis new materials for a more environmentally friendly dye-sensitized solar cell are investigated.

To model solar cells accurately one must solve coupled second order, partial, linear differential equations derived from Boltzmann's equation, continuity equations and electrostatics. Analytical solutions prove to be insufficient for modeling complex applications such as concentrating systems. A network model and computer programs which use a sophisticated one-dimensional solar cell model were developed to simulate nonuniformly illuminated cells in concentrating systems.This project's task was to make these programs more efficient and to simulate nonuniform illumination cases with higher intensity levels and with spectral variations previously untried. To this end, modifications were effected resulting in a factor of one hundred reduction in the error of gvalue, an important model parameter, a reduction in running time by a factor of ten for the best cases and no less than two for the worst, and an overall simplification of the modeling process.Presented herein are the results of the simulations performed by the model. Eleven cases of nonuniformity previously untested were modeled at different levels of metalization and degrees of nonuniformity. A comparison of the results obtained was also made to previous work done in this field. In addition to the results of the simulations, the actual computer programs of the network model are included. / Department of Physics and Astronomy

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 112-118). Also available in electronic format on the Internet.

Thesis (M.S.)--University of Toledo, 2008. / Typescript. "Submitted as partial fulfillments of the requirements for the Master of Science Degree in Physics." "A thesis entitled"--at head of title. Bibliography: leaves 41-42.