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Title: Low-cost back contact silicon solar cells

Abstract

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 between open circuit voltage and rear side passivation is discussed based on two-dimensional (2-D) computer simulations.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. Konstanz (DE)
Sponsoring Org.:
German Research Ministry
OSTI Identifier:
20006070
Resource Type:
Journal Article
Resource Relation:
Journal Name: IEEE Transactions on Electron Devices (Institute of Electrical and Electronics Engineers); Journal Volume: 46; Journal Issue: 10; Other Information: PBD: Oct 1999
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; SILICON SOLAR CELLS; COST; FABRICATION; DESIGN; BACK CONTACT SOLAR CELLS

Citation Formats

Kress, A., Kuehn, R., Fath, P., Willeke, G.P., and Bucher, E.. Low-cost back contact silicon solar cells. United States: N. p., 1999. Web. doi:10.1109/16.791988.
Kress, A., Kuehn, R., Fath, P., Willeke, G.P., & Bucher, E.. Low-cost back contact silicon solar cells. United States. doi:10.1109/16.791988.
Kress, A., Kuehn, R., Fath, P., Willeke, G.P., and Bucher, E.. 1999. "Low-cost back contact silicon solar cells". United States. doi:10.1109/16.791988.
@article{osti_20006070,
title = {Low-cost back contact silicon solar cells},
author = {Kress, A. and Kuehn, R. and Fath, P. and Willeke, G.P. and Bucher, E.},
abstractNote = {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 between open circuit voltage and rear side passivation is discussed based on two-dimensional (2-D) computer simulations.},
doi = {10.1109/16.791988},
journal = {IEEE Transactions on Electron Devices (Institute of Electrical and Electronics Engineers)},
number = 10,
volume = 46,
place = {United States},
year = 1999,
month =
}
  • Here, we present progress to develop low-cost interdigitated back contact solar cells with pc-Si/SiO 2/c-Si passivated contacts formed by plasma immersion ion implantation (PIII). PIII is a lower-cost implantation technique than traditional beam line implantation due to its simpler design, lower operating costs, and ability to run high doses (1E14-1E18 cm -2) at low ion energies (20 eV-10 keV). These benefits make PIII ideal for high throughput production of patterned passivated contacts, where high-dose, low-energy implantations are made into thin (20-200 nm) a-Si layers instead of into the wafer itself. For this work symmetric passivated contact test structures (~100 nmmore » thick) grown on n-Cz wafers with pH3 PIII doping gave implied open circuit voltage (iV oc) values of 730 mV with J o values of 2 fA/cm 2. Samples doped with B 2H 6 gave iV oc values of 690 mV and J o values of 24 fA/cm 2, outperforming BF 3 doping, which gave iV oc values in the 660-680 mV range. Samples were further characterized by SIMS, photoluminescence, TEM, EELS, and post-metallization TLM to reveal micro- and macro-scopic structural, chemical and electrical information.« 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 ({open_quotes}emitter wrap through{close_quotes}) from around 12{percent} to near 17{percent} 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 process using back-contact cells are described. {copyright} {ital 1999 American Institute ofmore » Physics.}« less
  • 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 earliestmore » 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.« less
  • No abstract prepared.