High-efficiency device research

Progress on research in high-efficiency silicon solar cells is presented. Topics addressed include: recombination measurement techniques, doped crystals, minority carrier transport, oxygen process in solar cells, solar cell models, loss mechanics in solar cells, high-efficiency metal insulators, dendritic web cells, and surface and bulk loss reduction by low-energy hydrogen doping

A theoretical analysis of the current-voltage characteristics of solar cells

The following topics are discussed: (1) dark current-voltage characteristics of solar cells; (2) high efficiency silicon solar cells; (3) short circuit current density as a function of temperature and the radiation intensity; (4) Keldysh-Franz effects and silicon solar cells; (5) thin silicon solar cells; (6) optimum solar cell designs for concentrated sunlight; (7) nonuniform illumination effects of a solar cell; and (8) high-low junction emitter solar cells

Solar cell module

An improved solar cell module for use in terrestrial environments is disclosed. It is characterized by: (1) an internally reflective plate having a planar surface of incidence and an opposed textured surface (2) a plurality of uniformly spaced silicon solar cells having the active surfaces thereof bonded to portions of the textured surface, and (3) a layer of diffusely reflective matter applied to the textured surface in surrounding relation with the solar cells for reflecting solar energy. The solar energy then strikes the surface of incidence at such angles as to be internally re-reflected and caused to progress toward the active surfaces of the solar cells, whereby concentration of incident flux on the solar cell is achieved without increased module depth

Effect of the shell material and confinement type on the conversion efficiency of the core/shell quantum dot nanocrystal solar cells

In this study, effects of the shell material and confinement type on the conversion efficiency of the core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in a detail manner. For this purpose, the conventional, i.e original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for conversion efficiency of silicon p-n junction solar cells, is modified in a simple and an effective way and calculated the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy ($E_g$) of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells and gives the same efficiency values for several QDNC solar cells with the same $E_g$. The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same $E_g$, become different depending upon the confinement type and shell material of the core/shell QDNCs and this is crucial in design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.Comment: 17 pages, 5 figures, Accepted by Journal of Physics: Condensed Matte

Solar cell shingle

A solar cell shingle was made of an array of solar cells on a lower portion of a substantially rectangular shingle substrate made of fiberglass cloth or the like. The solar cells may be encapsulated in flourinated ethylene propylene or some other weatherproof translucent or transparent encapsulant to form a combined electrical module and a roof shingle. The interconnected solar cells were connected to connectors at the edge of the substrate through a connection to a common electrical bus or busses. An overlap area was arranged to receive the overlap of a cooperating similar shingle so that the cell portion of the cooperating shingle may overlie the overlap area of the roof shingle. Accordingly, the same shingle serves the double function of an ordinary roof shingle which may be applied in the usual way and an array of cooperating solar cells from which electrical energy may be collected

Analytical determination of critical crack size in solar cells

Although solar cells usually have chips and cracks, no material specifications concerning the allowable crack size on solar cells are available for quality assurance and engineering design usage. Any material specifications that the cell manufacturers use were developed for cosmetic reasons that have no technical basis. Therefore, the Applied Solar Energy Corporation (ASEC) has sponsored a continuing program for the fracture mechanics evaluation of GaAs. Fracture mechanics concepts were utilized to develop an analytical model that can predict the critical crack size of solar cells. This model indicates that the edge cracks of a solar cell are more critical than its surface cracks. In addition, the model suggests that the material specifications on the allowable crack size used for Si solar cells should not be applied to GaAs solar cells. The analytical model was applied to Si and GaAs solar cells, but it would also be applicable to the semiconductor wafers of other materials, such as a GaAs thin film on a Ge substrate, using appropriate input data