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Abstract:
New Model Predicts Spontaneous Nanostructuring to Explain CIGS Thin-Film Efficiency

Austin, TX | Posted on October 31, 2005

Nanostructure Discovery by HelioVolt CEO Propels Solar Thin-Film Commercialization

After four years of research by HelioVolt CEO Dr. BJ Stanbery and his team, HelioVolt Corporation, a next-generation solar energy technology company, today announced the joint publication with researchers from the National Renewable Energy Lab (NREL) of experimental results confirming predictions of Dr. Stanbery's new theoretical model published in January, which explains much of the observed device physics and high performance characteristics of copper indium gallium selenide-based (CIGS) photovoltaics (PV). The Intra-Absorber Junction (IAJ) or Stanbery Model represents a key accomplishment in the scientific community's ongoing efforts to better understand the physics behind CIGS thin-films. The Stanbery model is a major leap forward for commercialization of CIGS photovoltaics.

After setting the world record for solar thin-film efficiency during his tenure at Boeing Aerospace Company, Dr. Stanbery focused his efforts on commercializing CIGS. CIGS photovoltaics have traditionally lagged behind silicon in terms of research and investment despite the dramatically lower materials cost of CIGS. Dr. Stanbery's discovery now equips the photovoltaic industry with the in-depth understanding of CIGS that is necessary to bring the material to the mass market. One key prediction of the Stanbery Model has now been confirmed by research at the National Renewable Energy Laboratory (NREL). The model asserts that CIGS performance is attributed to a process called "spontaneous nanostructuring" by which the material in the CIGS absorber layer arranges itself at the atomic level for optimum photovoltaic efficiency. In other words, Dr. Stanbery's model revealed that CIGS inherent physical properties make it one of nature's best solar materials.

Although its high-performance characteristics were evident in both small-area cells and large-area modules, advanced design and commercialization of CIGS photovoltaics have previously been hampered by a lack of fundamental understanding of the material. Particularly problematic to development, researchers found that CIGS devices made with the same composition and manufacturing methods inexplicably varied in performance.

Researchers were unable to identify consistent differences in high and low-efficiency material's absorber layers: initial investigation at the microscopic level showed a homogeneous, consistent structure. An explanation for the varied performance and consequent methods for improvement continued to prove elusive.

Dr. Stanbery deduced that the answer lies in structures that are orders of magnitude smaller: what appeared homogenous is actually organized at the nano-scale. The Stanbery Model now explains the perplexing behavior of CIGS devices, revealing the unique defect physics of the absorber layer by describing its nanostructure. According to the model, CIGS with compositions in the useful range for high performance PV spontaneously organizes to form a unique structure called a "percolation network" through which electrical currents flow smoothly.

"The nanostructure network that naturally occurs in CIGS is like creating separate express lanes for the positive and negative electrical charge carriers, reducing collisions between them and thereby increasing the current that flows outside of the device," said Dr. Stanbery. "Even when the composition of the CIGS devices varies, as long as this network exists the efficient flow of the charge carriers takes place." With this new understanding of how CIGS is structured and why the material performs the way it does, we are now able to effectively harness and improve upon what has long been the most efficient thin-film for photovoltaics.

For over 25 years, Dr. Stanbery has been dedicated to realizing a single vision: making photovoltaic power efficient, economically viable, and widely used. Renowned for his innovations in the design and manufacture of photovoltaic devices, Stanbery steered industry giant Boeing toward that goal, registering seven patents in thin-film photovoltaic technology, successfully manufacturing and deploying photovoltaic devices for spacecraft, and, in 1990, leading the team that achieved the world record in multi-junction thin-film cell efficiency, a distinction he still holds to this day. As Founder and CEO of HelioVolt, Dr. Stanbery is applying his fundamental understanding of CIGS thin-film to the commercialization of efficient, durable, CIGS photovoltaics incorporated into conventional building materials.

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About HelioVolt Corporation:
HelioVolt Corporation was founded in 2001 in order to develop and market new technology for applying thin-film photovoltaic coatings to conventional construction materials. The company's proprietary FASST process, based on rapid semiconductor printing, was invented by HelioVolt founder Dr. Billy J. Stanbery, an eminent expert within the international PV community in the materials science of CIS and related compound semiconductors. FASST is a low-cost, flexible manufacturing process for CIGS synthesis and is protected by both eight issued US patents and by global patents pending.

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Media Contact:
Caroline Venza
Antenna Group for HelioVolt
caroline@antennagroup.com
415-977-1939

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