Engineering Papers⌕ Search

Engineering topics

Carbajal, B. G.

Publications and source records attributed to Carbajal, B. G..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Automated array assembly, phase 2

Tasks of scaling up the tandem junction cell (TJC) from 2 cm x 2 cm to 6.2 cm and the assembly of several modules using these large area TJC's are described. The scale-up of the TJC was based on using the existing process and doing the necessary design activities to increase the cell area to an acceptably large area. The design was carried out using available device models. The design was verified and sample large area TJCs were fabricated. Mechanical and process problems occurred causing a schedule slippage that resulted in contract expiration before enough large-area TJCs were fabricated to populate the sample tandem junction modules (TJM). A TJM design was carried out in which the module interconnects served to augment the current collecting buses on the cell. No sample TJMs were assembled due to a shortage of large-area TJCs.

Carbajal, B. G.↗
NASA NTRS1979

A device model for the tandem junction solar cell

A conceptual device model has been developed to explain operation of the tandem junction cell (TJC) when back contacts only are used. Operation and parameters of the cell are explained by transistor action. Experimental observations are presented which confirm that current is collected for carrier generation in the front uncontacted n(plus) region. The model should be useful as a guideline to optimize the TJC by application of transistor design principles.

Matzen, W. T.↗
NASA NTRS1979

Design considerations for the Tandem Junction Solar Cell

Structure and operation of the tandem junction cell (TJC) are described. The impact of using only back contacts is discussed. A model is presented which explains operation of the TJC in terms of transistor action. The model is applied to predict TJC performance as a function of physical parameters.

Matzen, W. T.↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The Automated Array Assembly Task, Phase 2 of the Low Cost Silicon Solar Array Project is a process development task. The contract provides for the fabrication of modules from large area tandem junction cells (TJC). During this quarter, effort was focused on the design of a large area, approximately 36 sq cm, TJC and process verification runs. The large area TJC design was optimized for minimum I squared R power losses. In the TJM activity, the cell-module interfaces were defined, module substrates were formed and heat treated and clad metal interconnect strips were fabricated.

Carbajal, B. G.↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The solar cell module process development activities in the areas of surface preparation are presented. The process step development was carried out on texture etching including the evolution of a conceptual process model for the texturing process; plasma etching; and diffusion studies that focused on doped polymer diffusion sources. Cell processing was carried out to test process steps and a simplified diode solar cell process was developed. Cell processing was also run to fabricate square cells to populate sample minimodules. Module fabrication featured the demonstration of a porcelainized steel glass structure that should exceed the 20 year life goal of the low cost silicon array program. High efficiency cell development was carried out in the development of the tandem junction cell and a modification of the TJC called the front surface field cell. Cell efficiencies in excess of 16 percent at AM1 have been attained with only modest fill factors. The transistor-like model was proposed that fits the cell performance and provides a guideline for future improvements in cell performance.

Carbajal, B. G.↗
NASA NTRS1979

High Efficiency Cell Development

The specific activity was to improve the tandem junction Cell (TJC) as a high efficiency solar cell. The TJC development was to be consistent with module assembly and should contribute to the overall goals of the Low-Cost Solar Array Project. During 1978, TJC efficiency improved from approximately 11 percent to approximately 16 percent (AMI). Photogenerated current densities in excess of 42 mA/sq cm were observed at AMO. Open circuit voltages as high as 0.615 V were measured at AMO. Fill factor was only 0.68 - 0.75 due to a nonoptimum metal contact design. A device model was conceived in which the solar cell is modelled as a transitor. There are virtually no interconnect or packaging factor systems and the TJC is compatible with all conventional module fabrication systems. A modification of the TJC, the Front Surface Field (FSF) cell, was also explored.

Carbajal, B. G.↗
NASA NTRS1978

Optimized solar module design

The minimum cost per unit of power output from flat plate solar modules can most likely be achieved through efficient packaging of higher efficiency solar cells. This paper outlines a module optimization method which is broadly applicable, and illustrates the potential results achievable from a specific high efficiency tandem junction (TJ) cell. A mathematical model is used to assess the impact of various factors influencing the encapsulated cell and packing efficiency. The optimization of the packing efficiency is demonstrated. The effect of encapsulated cell and packing efficiency on the module add-on cost is shown in a nomograph form.

Santala, T.↗
NASA NTRS1977

Automated array assembly task, phase 1

State-of-the-art technologies applicable to silicon solar cell and solar cell module fabrication were assessed. The assessment consisted of a technical feasibility evaluation and a cost projection for high volume production of solar cell modules. Design equations based on minimum power loss were used as a tool in the evaluation of metallization technologies. A solar cell process sensitivity study using models, computer calculations, and experimental data was used to identify process step variation and cell output variation correlations.

Carbajal, B. G.↗
NASA NTRS1977

Automated array assembly task, phase 1

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Carbajal, B. G.↗
NASA NTRS1977

Automated array assembly task, phase 1

An assessment of state-of-the-art technologies that are applicable to silicon solar cell and solar cell module fabrication is provided. The assessment consists of a technical feasibility evaluation and a cost projection for high-volume production of silicon solar cell modules. The cost projection was approached from two directions; a design-to-cost analysis assigned cost goals to each major process element in the fabrication scheme, and a cost analysis built up projected costs for alternate technologies for each process element. A technical evaluation was used in combination with the cost analysis to identify a baseline low cost process. A novel approach to metal pattern design based on minimum power loss was developed. These design equations were used as a tool in the evaluation of metallization technologies.

Carbajal, B. G.↗
NASA NTRS1976

Optimized metallization patterns for large-area silicon solar cells

Design criteria is presented for optimizing the front-surface metallization pattern of large-area silicon solar cells. A computer program calculates the spacing of metal fingers which minimizes resistive and shadowing losses. Finger spacing and efficiency for the optimum design are presented as a function of finger width and cell size. It is shown that quantitative evaluation of metallization pattern options can be made without cell fabrication.

Matzen, W. T.↗