Applications > Solar Photovoltaic (PV) Energy

Many types of photovoltaic (PV) cells use transparent conductive coatings to transmit or collect electrical charge. Presently many rely on metal oxides layers or opaque silver lines to perform this function. The motivation for replacing current coatings or layers is their inherent brittleness, high deposition cost, and high deposition temperatures; leading to reduced performance especially on thin substrates. Alternatively, Invisicon® coatings can overcome these shortcomings while offering the ability to be applied in atmospheric conditions using low cost coating processes.

Green carbon nanotubes

Invisicon is ideal for thin film PV:

  • p-type conductive network
  • Solution processed at low temperature
  • Low cost deposition
  • Flexible and durable
  • Porous electrode compatible with substrate and top layers

Eikos is developing Invisicon specifically to meet the needs of a wide variety of PV cell types like CIGS and OPV shown below. Much of this effort is sponsored by our government and commercial clients seeking to overcome limitations imposed by decades-old conductive coating technologies.

CIGS Invisicon replaces n-ZnO


Organic PV

For example, the US Department of Energy (DOE) awarded a multiyear grant for Eikos Inc. to investigate the feasibility of developing and utilizing Transparent Conducting Coatings (TCCs) based on Invisicon for solar cell applications.

Eikos has made significant progress in developing these materials through a close collaboration with NREL. Early versions of this TCC technology have been used to fabricate award winning laboratory scale solar cells, and have yielded several groundbreaking peer reviewed papers. Proof-of-concept solar cells served to demonstrate the advantages of using nanotubes in a wide variety of solar cell types and in entirely new cell structures. Eikos continues to develop the purification, dispersion, formulation, and coating of Invisicon for solar power.

Milestones in Photovoltaics
Cell Type Structure Efficiency, %
CIGS 1 SWNT/Cds/CIGS/Mo 4.10
CIGS 2 SWNT/Parylene/SWNT/CdS/CIGS/Mo 8.22
CIGS 3 SWNT/i-ZnO/CdS/CIGS/Mo 12.60
CIGS 4 SWNT Contacts/SWNT/i-ZnO/CdS/CIGS/Mo 12.98
CdTe 1 CTO/ZTOCdS/CdTe/CuTe/SWNT 12.4

This research:

  • Was recognized as the ‘Most Outstanding in Novel Devices and Materials’ at the 4th World Conference on Photovoltaic Energy Conversion.
  • Was awarded by Wall Street Journal as the best new material technology for PV and like devices.
  • Several scientific peer reviewed publications, including 1st of their kind PV devices.

Select publications resulting from this work

  1. “Organic solar cells with carbon nanotubes replacing In2O3:Sn as the transparent electrode,” J. van de Lagemaat, T.M. Barnes, G. Rumbles, S.E. Shaheen, and T.J. Coutts, C. Weeks, I. Levitsky, J. Peltola, and P. Glatkowski, Applied Physics Letters, 88, 233503, 2006.            

  2. “Replacement of Transparent Conductive Oxides by Single-Wall Carbon Nanotubes in Cu(In,Ga)Se2-Based Solar Cells,” M.A. Contreras, T. Barnes, J. van de Lagemaat, G. Rumbles, T.J. Coutts, C. Weeks, P. Glatkowski, I. Levitsky, J. Peltola, D. A. Britz, Journal of Physical Chemistry C, 38, 14045-14048, 2007.  

  3. “Single-wall carbon nanotube networks as a transparent back contact in CdTe solar cells,” T. M. Barnes, X. Wu, J. Zhou, A. Duda, J. van de Lagemaat, and T. J. Coutts, C. L. Weeks, D. A. Britz, and P. Glatkowski, Applied Physics Letters, 90, 243503, 2007.

  4. “Single-Wall Carbon Nanotubes as Transparent Electrodes for Photovoltaics,” C. Weeks, J. Peltola, I. Levitsky   P. Glatkowski, J. van de Lagemaat, G. Rumbles, T. Barnes, T. Coutts, Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, Vol 1, 295-297, May 2006.

Other examples of Eikos solar PV work include:

Using Invisicon, the world’s only high performance transparent hole conductor, to create the first >20% efficient thin film photovoltaics (TFPVs) for power in space. Eikos has demonstrated that Invisicon is capable of maintaining conductivity and transparency under the manufacturing conditions required to produce a TFPV and is integrating Invisicon into a dual junction thin film PV that is capable of specific power as high as 1,000 W/kg.

transparent wide bandgap PV
  Schematic of a transparent wide bandgap PV (top cell only) with an Invisicon hole conducting back electrode.  

Unlike the crystalline triple junction PVs used in present space power systems, TFPVs are more radiation resistant, lightweight, flexible, and capable of low cost production. To displace current triple-junction PVs, TFPVs must be made more efficient in addition to being lightweight, flexible, and low cost. The most technologically feasible way to achieve these characteristics is to make a “tandem” device by stacking a wide band gap TFPV on top of a narrow band gap TFPV. Invisicon offers several unique attributes which enable such a cell to be manufactured.

Invisicon  for High Efficiency Thin Film Photovoltaics

Eikos, Inc is integrating Invisicon to increase the performance of amorphous silicon thin film photovoltaics. Eikos is developing module-level improvements in multifunctional coatings that act as transparent conductive electrodes and light trapping/anti-reflective (AR) coatings.

Finally Eikos is working on several other product development projects exploiting the unique capabilities of Invisicon to enable new solar cell architectures, high performance, and lower cost manufacturing.  Please contact us if your technology could benefit form the Invisicon advantage.

Carbon Nanotube
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