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Title: Heterojunction solar cell with passivated emitter surface

Abstract

A high-efficiency heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. A passivating window layer of defined composition is disposed over the emitter layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the window layer. 1 fig.

Inventors:
;
Publication Date:
OSTI Identifier:
7111066
Patent Number(s):
US 5316593; A
Application Number:
PPN: US 7-977109
Assignee:
Midwest Research Inst., Kansas City, MO (United States) PTO; EDB-94-099126
DOE Contract Number:
AC02-83CH10093
Resource Type:
Patent
Resource Relation:
Patent File Date: 16 Nov 1992
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; GALLIUM PHOSPHIDE SOLAR CELLS; ENERGY EFFICIENCY; INDIUM PHOSPHIDE SOLAR CELLS; ANTIREFLECTION COATINGS; DESIGN; COATINGS; DIRECT ENERGY CONVERTERS; EFFICIENCY; EQUIPMENT; PHOTOELECTRIC CELLS; PHOTOVOLTAIC CELLS; SOLAR CELLS; SOLAR EQUIPMENT; 140501* - Solar Energy Conversion- Photovoltaic Conversion

Citation Formats

Olson, J.M., and Kurtz, S.R. Heterojunction solar cell with passivated emitter surface. United States: N. p., 1994. Web.
Olson, J.M., & Kurtz, S.R. Heterojunction solar cell with passivated emitter surface. United States.
Olson, J.M., and Kurtz, S.R. 1994. "Heterojunction solar cell with passivated emitter surface". United States. doi:.
@article{osti_7111066,
title = {Heterojunction solar cell with passivated emitter surface},
author = {Olson, J.M. and Kurtz, S.R.},
abstractNote = {A high-efficiency heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. A passivating window layer of defined composition is disposed over the emitter layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the window layer. 1 fig.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1994,
month = 5
}
  • A high-efficiency heterojunction solar cell wherein a thin emitter layer (preferably Ga.sub.0.52 In.sub.0.48 P) forms a heterojunction with a GaAs absorber layer. A passivating window layer of defined composition is disposed over the emitter layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the window layer.
  • The performance of passivated emitter and rear (PERC) solar cells made of p-type Si wafers is often limited by recombination in the phosphorus-doped emitter. To overcome this limitation, a realistic PERC solar cell is simulated, whereby the conventional phosphorus-doped emitter is replaced by a thin, crystalline gallium phosphide (GaP) layer. The resulting GaP/Si PERC cell is compared to Si PERC cells, which have (i) a standard POCl{sub 3} diffused emitter, (ii) a solid-state diffused emitter, or (iii) a high efficiency ion-implanted emitter. The maximum efficiencies for these realistic PERC cells are between 20.5% and 21.2% for the phosphorus-doped emitters (i)–(iii),more » and up to 21.6% for the GaP emitter. The major advantage of this GaP hetero-emitter is a significantly reduced recombination loss, resulting in a higher V{sub oc}. This is so because the high valence band offset between GaP and Si acts as a nearly ideal minority carrier blocker. This effect is comparable to amorphous Si. However, the GaP layer can be contacted with metal fingers like crystalline Si, so no conductive oxide is necessary. Compared to the conventional PERC structure, the GaP/Si PERC cell requires a lower Si base doping density, which reduces the impact of the boron-oxygen complexes. Despite the lower base doping, fewer rear local contacts are necessary. This is so because the GaP emitter shows reduced recombination, leading to a higher minority electron density in the base and, in turn, to a higher base conductivity.« less
  • The optimum emitter surface dopant concentration (N/sub s/) in passivated silicon solar cells is found for different base resistivities with the help of a computer model. The model takes into account not only the band-gap narrowing, Auger and surface recombination effects on the dark saturation current, but it also considers the variation of series resistance as the impurity concentration changes. The results obtained with the model show different behavior for passivated and nonpassivated solar cells. The open-circuit voltage and the conversion efficiency of nonpassivated solar cells is almost independent of the surface impurity concentration when this parameter is greater thanmore » 2 x 10/sup 19/ cm/sup -3/. On the other hand, for passivated solar cells the optimum value is in the range 2.5 x 10/sup 19/ cm/sup -3/ < or =N/sub s/<5 x 10/sup 19/ cm/sup -3/ for typical base resistivities. Furthermore, it is confirmed that even when N/sub s/ is high (N/sub s/>1 x 10/sup 20/ cm/sup -3/) there is an advantage in efficiency of passivated solar cells over those which have a high recombination at the surface. However, in order to increase the efficiency appreciably N/sub s/ has to be optimized. The model also gives a procedure to optimize the grid design simultaneously with the surface concentration, assuming the other parameters are optimum.« less
  • We explore substoichiometric molybdenum trioxide (MoO{sub x}, x < 3) as a dopant-free, hole-selective contact for silicon solar cells. Using an intrinsic hydrogenated amorphous silicon passivation layer between the oxide and the silicon absorber, we demonstrate a high open-circuit voltage of 711 mV and power conversion efficiency of 18.8%. Due to the wide band gap of MoO{sub x}, we observe a substantial gain in photocurrent of 1.9 mA/cm{sup 2} in the ultraviolet and visible part of the solar spectrum, when compared to a p-type amorphous silicon emitter of a traditional silicon heterojunction cell. Our results emphasize the strong potential for oxides as carrier selectivemore » heterojunction partners to inorganic semiconductors.« less
  • No abstract prepared.