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Title: High Efficiency Cascade Solar Cells

Abstract

This report summarizes the main work performed by New Mexico State University and University of Houston on a DOE sponsored project High Efficiency Cascade Solar Cells. The main tasks of this project include materials synthesis, characterization, theoretical calculations, organic solar cell device fabrication and test. The objective of this project is to develop organic nano-electronic-based photovoltaics. Carbon nanotubes and organic conjugated polymers were used to synthesize nanocomposites as the new active semiconductor materials that were used for fabricating two device architectures: thin film coating and cascade solar cell fiber. Chemical vapor deposition technique was employed to synthesized a variety of carbon nanotubes (single-walled CNT, doubled-walled CNT, multi-walled CNT, N-doped SWCNT, DWCNT and MWCNT, and B-doped SWCNT, DWCNT and MWCNT) and a few novel carbon structures (CNT-based nanolance, nanocross and supported graphene film) that have potential applications in organic solar cells. Purification procedures were developed for removing amorphous carbons from carbon nanotubes, and a controlled oxidation method was established for partial truncation of fullerene molecules. Carbon nanotubes (DWCNT and DWCNT) were functionalized with fullerenes and dyes covalently and used to form nanocomposites with conjugated polymers. Biologically synthesized Tellurium nanotubes were used to form composite with the conjugated polymers as well, whichmore » generated the highest reported optical limiting values from composites. Several materials characterization technique including SEM/TEM, Raman, AFM, UV-vis, adsorption and EDS were employed to characterize the physical and chemical properties of the carbon nanotubes, the functionalized carbon nanotubes and the nanocomposites synthesized in this project. These techniques allowed us to have a spectroscopic and morphological control of the composite formation and to understand the materials assembled. A parallel 136-CPU Beowulf computer cluster was launched intended to be used as the main computational tool for the theoretical part of this project. The mechanism of surface carboxylation of pristine and defective carbon nanotubes were studied using the computation method. Theoretical studies of boron- and nitrogen-doped carbon nanotubes functionalized with chemical groups, and CdSe/ZnSe, ZnSe/CdSe, CdTe/ZnTe, and ZnTe/CdTe core-shell semiconductor nanoparticles embedded in electroactive polymers were also carried out. We have successfully fabricated singular champion cells with Voc of 0.6 V and Jsc of 15 mA, and developed the pixel cells and with a working areas over 25mm2, 2.5 % efficiency for a multicell arrangement, and a stability of 40% of their initial efficiency after 11,000 minutes. We have also demonstrated the feasibility of using a gold film as an alternative semi-transparent electrode for organic solar cell applications. An efficiency of 1.9 % (JSC of 7.01 mA/cm2, VOC of 0.55 V, FF of 0.49) can be reached by using the gold film as an anode instead of ITO. Two new vertical organic solar cell architectures: stack cells and wrap cells, suitable as an alternative to planar devices were developed as well. We have proved the feasibility of replacing ITO with more traditional metals without hindering performance, and developed natural encapsulation techniques during device fabrication. Optical modeling of the stack cells was also performed to enhance our understanding of this device configuration.« less

Authors:
Publication Date:
Research Org.:
New Mexico State University
Sponsoring Org.:
EERE: Solar Energy Technologies Program
OSTI Identifier:
1015879
Report Number(s):
DOE/GO/88008-1
DOE Contract Number:
FG36-08GO88008
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
Organic solar cells, carbon nanotubes, cascade, nanocomposites, photovoltaics

Citation Formats

Shuguang Deng, Seamus Curran, Igor Vasiliev. High Efficiency Cascade Solar Cells. United States: N. p., 2010. Web.
Shuguang Deng, Seamus Curran, Igor Vasiliev. High Efficiency Cascade Solar Cells. United States.
Shuguang Deng, Seamus Curran, Igor Vasiliev. 2010. "High Efficiency Cascade Solar Cells". United States. doi:.
@article{osti_1015879,
title = {High Efficiency Cascade Solar Cells},
author = {Shuguang Deng, Seamus Curran, Igor Vasiliev},
abstractNote = {This report summarizes the main work performed by New Mexico State University and University of Houston on a DOE sponsored project High Efficiency Cascade Solar Cells. The main tasks of this project include materials synthesis, characterization, theoretical calculations, organic solar cell device fabrication and test. The objective of this project is to develop organic nano-electronic-based photovoltaics. Carbon nanotubes and organic conjugated polymers were used to synthesize nanocomposites as the new active semiconductor materials that were used for fabricating two device architectures: thin film coating and cascade solar cell fiber. Chemical vapor deposition technique was employed to synthesized a variety of carbon nanotubes (single-walled CNT, doubled-walled CNT, multi-walled CNT, N-doped SWCNT, DWCNT and MWCNT, and B-doped SWCNT, DWCNT and MWCNT) and a few novel carbon structures (CNT-based nanolance, nanocross and supported graphene film) that have potential applications in organic solar cells. Purification procedures were developed for removing amorphous carbons from carbon nanotubes, and a controlled oxidation method was established for partial truncation of fullerene molecules. Carbon nanotubes (DWCNT and DWCNT) were functionalized with fullerenes and dyes covalently and used to form nanocomposites with conjugated polymers. Biologically synthesized Tellurium nanotubes were used to form composite with the conjugated polymers as well, which generated the highest reported optical limiting values from composites. Several materials characterization technique including SEM/TEM, Raman, AFM, UV-vis, adsorption and EDS were employed to characterize the physical and chemical properties of the carbon nanotubes, the functionalized carbon nanotubes and the nanocomposites synthesized in this project. These techniques allowed us to have a spectroscopic and morphological control of the composite formation and to understand the materials assembled. A parallel 136-CPU Beowulf computer cluster was launched intended to be used as the main computational tool for the theoretical part of this project. The mechanism of surface carboxylation of pristine and defective carbon nanotubes were studied using the computation method. Theoretical studies of boron- and nitrogen-doped carbon nanotubes functionalized with chemical groups, and CdSe/ZnSe, ZnSe/CdSe, CdTe/ZnTe, and ZnTe/CdTe core-shell semiconductor nanoparticles embedded in electroactive polymers were also carried out. We have successfully fabricated singular champion cells with Voc of 0.6 V and Jsc of 15 mA, and developed the pixel cells and with a working areas over 25mm2, 2.5 % efficiency for a multicell arrangement, and a stability of 40% of their initial efficiency after 11,000 minutes. We have also demonstrated the feasibility of using a gold film as an alternative semi-transparent electrode for organic solar cell applications. An efficiency of 1.9 % (JSC of 7.01 mA/cm2, VOC of 0.55 V, FF of 0.49) can be reached by using the gold film as an anode instead of ITO. Two new vertical organic solar cell architectures: stack cells and wrap cells, suitable as an alternative to planar devices were developed as well. We have proved the feasibility of replacing ITO with more traditional metals without hindering performance, and developed natural encapsulation techniques during device fabrication. Optical modeling of the stack cells was also performed to enhance our understanding of this device configuration.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2010,
month = 9
}

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  • The objective of this research has been the continued development of the technology needed to fabricate two-junction cascade solar cells having conversion efficiencies of 30 percent or more under multisun illumination. Research has been carried out in a number of different III-V semiconductor materials systems that are potential candidates for a cascade solar cell design. Work has focused on the development of a compatible combination of materials required for the monolithic, multilayer structure using several different epitaxial growth techniques. Materials receiving principal attention during the past year have been GaA1As, GaInP, and GaA1AsSb for the high bandgap top cell andmore » GaInAs, GaAsSb, and GaAs for the low bandgap bottom cell. Liquid phase, vapor phase, and organometallic-chemical vapor deposition growth techniques have been explored. Progress is detailed.« less
  • Progress is reported in the following areas: AlGaAsSb/GaAsSb materials development, GaInP materials development via VPE, GaAlAs/GaAs cell development, and OM/CVD studies. Spectral response, V-I characteristics, and electron microprobe analysis results are presented. (WHK)
  • The present experimental work is focusing principally on the GaAlAsSb/GaAsSb cascade cell, which is of particular interest since it offers the optimum bandgap combination of 1.8/1.2 eV for maximum efficiency in high temperature concentrator applications. The major problem experienced thus far in the development of the AlGaAsSb/GaAsSb cell has been the relatively low open circuit voltages (V/sub oc/) that have been characteristic of both top and bottom cell junctions. Addressing this problem continues to be a major objective of the continued development of this cell. The AlGaAs/GaAs cell is being retained as a backup to the antimonide cell. Although themore » AlGaAs/GaAs cell is not capable of achieving the optimum 1.8/1.2 eV bandgap combination, it avoids problems associated with lattice mismatch with the GaAs substrate and offers a more proven materials technology. Computer analysis of this cell shows that a 1.92/1.43 eV bandgap combination is capable of achieving an active area efficiency of about 27% at Am1.5, 300/sup 0/K, 1 sun. At 500 suns this cell is predicted to have efficiency values of about 30% at 300/sup 0/K and 20% at 475/sup 0/K. Experimental AlGaAs/GaAs cells without AR coatings have exhibited measured efficiency values of about 16% at AM1.5, 1 sun. This development effort has been focusing on performance improvement through improved tunnel junction performance, better ohmic contacts, and an optimized AR coating and on fabricating larger area cells.« less
  • Research has continued in the development of selected ternary and quaternary III-V materials that are potential candidates for cascade solar cell applications. In addition, various simple and multi-junction cascade solar cell components have been fabricated and evaluated in a continuing study of several different solar cell designs (materials combinations). During the present reporting period, work has concentrated on the following major areas: GaAlAs/GaAs cell development; AlGaAsSb/GaAsSb materials development; GaInP materials development via VPE; inverted structure development; and MO/CVD growth system work at NCSU. Progress in each of these areas is summarized.
  • The goal of the program reported has been to develop the technology required to fabricate two-junction, monolithic cascade solar cells with potential conversion efficiencies greater than 30% in an AM2, 400 to 1000 sun environment. The modeling which stimulated the interest in the antimonide cell is described, as are the thermodynamic factors which place fundamental restraints on material growth by liquid phase epitaxy (LPE). A description of the LPE growth is presented for each of the components of the cascade structure. The growth of GaAsSb by organometallic vapor phase epitaxy (OM-VPE) is also described. The experimental results for individually grownmore » components and cascade structures are described, including: dark and illuminated current-voltage characteristics, short-circuit current responses, and fill factor, diffusion length, and efficiency measurements. The cell structure and significant experimental results are also outlined for AlGaAs/GaAs system. (LEW)« less