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Title: Review of Back Contact Silicon Solar Cells for Low-Cost Application

Abstract

Back contact solar cells hold significant promise for increased performance in photovoltaics for the near future. Two major advantages which these cells possess are a lack of grid shading loss and coplanar interconnection. Front contacted cells can have up to 10% shading loss when using screen printed metal grids. A front contact cell must also use solder connections which run from the front of one cell to the back of the next for series interconnection. This procedure is more difficult to automate than the case of co-planar contacts. The back contact cell design is not a recent concept. The earliest silicon solar cell developed by Bell Labs was a back contact device. There have been many design modifications to the basic concept over the years. To name a few, there is the Interdigitated Back Contact (IBC) cell, the Stanford Point contact solar cell, the Emitter Wrap Through (EWT), and its many variations. A number of these design concepts have demonstrated high efficiency. The SunPower back contact solar cell holds the efficiency record for silicon concentrator cells. The challenge is to produce a high efficiency cell at low cost using high throughput techniques. This has yet to be achieved with amore » back contact cell design. The focus of this paper will be to review the relevant features of back contact cells and progress made toward the goal of a low cost version of this device.« less

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
9692
Report Number(s):
SAND99-2025C
TRN: AH200125%%139
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: 9th Workshop on Crystalline Silicon Materials and Processes, Breckenridge, CO (US), 08/10/1999; Other Information: PBD: 4 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; BACK CONTACT SOLAR CELLS; CONCENTRATORS; DESIGN; EFFICIENCY; MODIFICATIONS; PERFORMANCE; SCREENS; SILICON; SILICON SOLAR CELLS; SOLAR CELLS

Citation Formats

Smith, David D. Review of Back Contact Silicon Solar Cells for Low-Cost Application. United States: N. p., 1999. Web.
Smith, David D. Review of Back Contact Silicon Solar Cells for Low-Cost Application. United States.
Smith, David D. Wed . "Review of Back Contact Silicon Solar Cells for Low-Cost Application". United States. doi:. https://www.osti.gov/servlets/purl/9692.
@article{osti_9692,
title = {Review of Back Contact Silicon Solar Cells for Low-Cost Application},
author = {Smith, David D.},
abstractNote = {Back contact solar cells hold significant promise for increased performance in photovoltaics for the near future. Two major advantages which these cells possess are a lack of grid shading loss and coplanar interconnection. Front contacted cells can have up to 10% shading loss when using screen printed metal grids. A front contact cell must also use solder connections which run from the front of one cell to the back of the next for series interconnection. This procedure is more difficult to automate than the case of co-planar contacts. The back contact cell design is not a recent concept. The earliest silicon solar cell developed by Bell Labs was a back contact device. There have been many design modifications to the basic concept over the years. To name a few, there is the Interdigitated Back Contact (IBC) cell, the Stanford Point contact solar cell, the Emitter Wrap Through (EWT), and its many variations. A number of these design concepts have demonstrated high efficiency. The SunPower back contact solar cell holds the efficiency record for silicon concentrator cells. The challenge is to produce a high efficiency cell at low cost using high throughput techniques. This has yet to be achieved with a back contact cell design. The focus of this paper will be to review the relevant features of back contact cells and progress made toward the goal of a low cost version of this device.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Aug 04 00:00:00 EDT 1999},
month = {Wed Aug 04 00:00:00 EDT 1999}
}

Conference:
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  • No abstract prepared.
  • Back-contacted solar cells offer multiple advantages in regard of reducing module assembling costs and avoiding grid shadowing losses. The investigated emitter-wrap=through (EWT) device design has an electrical connection of the front emitter and the rear emitter grid in form of small holes drilled into the crystalline silicon wafer. The thus obtained cell structure is especially suitable for low-cost base material with small minority carrier diffusion lengths. Different industrially applicable solar cell manufacturing processes for EWT devices are described and compared. The latest experimental results are presented and interpreted; especially the photo-current is found to be distinctly increased. The relation betweenmore » open circuit voltage and rear side passivation is discussed based on two-dimensional (2-D) computer simulations.« less
  • The buried contact (BC) technology has demonstrated both an efficiency and cost advantage over conventional screen printed solar cells. New BC structures, in particular the double sided (DS) BC cell, allow further improvements in cost and efficiency. Improvements in efficiency arise through improved rear surface passivation. Experimental results from DSBC cells using various passivation methods demonstrate that a floating junction (FJ) passivates as well as passivation schemes used with high efficiency cells. 2D analysis and experimental results both show localized defects have prevented FJ passivation from achieving its potential and that optimization of the rear doping or by bifacial operationmore » can improve performance.« less
  • A variety of techniques may be used for photovoltaic energy systems. Concentrated or not concentrated sunlight may be employed, and a number of materials can be used, including silicon, gallium arsenide, cadmium sulfide, and cadmium telluride. Most of the experience, however, has been obtained with silicon cells employed without sunlight concentration. An industrial base exists at present for producing solar cells at a price in the range from $15 to $30 per peak watt. A major federal program has the objective to reduce the price of power provided by silicon solar systems to approximately $1 per peak watt in themore » early 1980's and $0.50 per watt by 1986. The approaches considered for achieving this objective are discussed.« less
  • This paper summarizes recent progress in the development of back-contact crystalline-silicon (c-Si) solar cells and modules at Sandia National Laboratories. Back-contact cells have potentially improved efficiencies through the elimination of grid obscuration and allow for significant simplifications in the module assembly process. Optimization of the process sequence has improved the efficiency of our back-contact cell (emitter wrap through) from around 12% to near 17% in the past 12 months. In addition, recent theoretical work has elucidated the device physics of emitter wrap-through cells. Finally, improvements in the assembly processing back-contact cells are described.