PHOTOVOLTAICS: Thermophotovoltaic device design has double the efficiency

While photovoltaic (PV) cells that extract energy from sunlight are getting much attention, another type of PV device has great promise too. Semiconductor thermophotovoltaic (TPV) devices are similar to solar cells but have a smaller bandgap, allowing them to extract energy from heat sources such as waste heat from power plants, automobiles, and even thermal solar power sources. Increasing the efficiency of TPV devices could change them from a rarely used curiosity to an important tool for increasing the effectiveness of energy extraction worldwide.

Jian Yin and Roberto Paiella of Boston University (BU; Boston, MA) are studying the use of intersubband transitions in quantum-cascade (QC) semiconductor structures to capture energy from photons over a broadband range in the IR.1 This sort of structure, which has multiple junctions each with different bandgap energies, is already used in some IR photodetectors in a simpler form in which the cascade stages are identical.

The two BU researchers have completed a performance analysis of QC TPV structures to determine their ultimate efficiency and have found that their use could double the output electrical power of present-day TPV devices.

Click to Enlarge
A quantum-cascade TPV structure contains an embedded grating that scatters light to maximize absorption of both TM and TE polarized light.

Four-stage device

The structure they selected is based on an indium gallium arsenide (In0.67Ga0.33As) p-n junction with a 0.6 eV bandgap integrated with a series of differing QC stages based on In0.83Ga0.17As/AlAs0.65Sb0.35 quantum wells. The proportions of elements in the QC stages is close to that in the p-n junction, eliminating net strain accumulation and accompanying defect formation. Because the device naturally absorbs only TM-polarized light, an embedded 2D reflection grating scatters the TE-polarized photons so that they are also absorbed.

The model assumed a device with four different QC structures subjected to blackbody radiation with a temperature of 1300 K. The high-absorption band of the combined four structures reached from just over 0.2 eV to just under 0.6 eV, or a good portion of the 1300 K blackbody-radiation spectrum.

The electrical current density of all four stages was the same by design—about 4 A/cm2. The model showed the TPV device had a short-circuit current density, open-circuit voltage, and fill factor of 4.9 A/cm2, 0.92 V, and 63%, respectively. Especially important, its maximum output electrical power density was just over 2.8 W/cm2. The researchers also used their model to calculate the energy conversion of the best existing TPV device at 1300 K—a photodiode that has experimentally produced an energy conversion of about 0.8 W/cm2. The model, which was of the detector's p-n junction by itself, gave an efficiency of 1.4 W/cm2, or half that of the QC design. —John Wallace

REFERENCE

1. J. Yin and R. Paiella, Appl. Phys. Lett., 98, 041103 (2011).

More Laser Focus World Current Issue Articles
More Laser Focus World Archives Issue Articles

Most Popular Articles

Webcasts

Opportunities in the Mid-IR

The technology for exploiting the mid-IR is developing rapidly:  it includes quantum-cascade lasers and other sources, spectroscopic instruments of many...

Fiber Optic Sensors – Fundamentals, Principles and Applications

In this webcast, sponsored by Nufern, we focus on optical fiber sensing technology.  Fundamental concepts will be presented first, followed by the under...

Infinite Possibilities – Easily Combining Scanner and Servo Motion

High precision motion control applications such as laser micromachining, 2-photon polymerization, glass panel and film patterning, and additive manufacturing...

Solutions in Search of Problems: What Spectroscopy Can Do for You

Spectroscopy is so pervasive that most of us take it for granted. We use it for routine laboratory and test measurements without appreciating how those same ...

Technical Digests

HIGH-ENERGY LASER COATINGS: Eliminating laser damage proactively

High-power and high-energy thin-film antireflection coatings for laser optics require careful des...
Sponsored by

LIBS -- spectroscopy for remote identification of materials

Laser-induced-breakdown spectroscopy (LIBS) uses a pulsed laser to vaporize a small sample of a s...
Sponsored by

Laser Tools for Materials Processing

Laser materials processing requires not only the appropriate industrial laser system, but also a ...
Sponsored by

Click here to have your products listed in the Laser Focus World Buyers Guide.

RELATED PRODUCTS

Phantom v1610

Phantom v1610 high-speed digital camera can shoot 1 million FPS.

Phantom v711

Phantom v711 high-speed digital camera

Evolve 128 EMCCD Camera

Quantitative high performance with extreme sensitivity for low-light applications.

RELATED COMPANIES

Surface Optics Corp

Designs and manufactures hyperspectral and multispectral imagers operating from the ult...

Optics Balzers AG

Possesses comprehensive know-how in optical thin-film coatings and components, glass pr...

Cremat Inc

Manufactures and supplies charge-sensitive preamplifiers for use in nuclear and x-ray d...

Social Activity

  •  
  •  
  •  
  •  
  •  
Copyright © 2007-2014. PennWell Corporation, Tulsa, OK. All Rights Reserved.PRIVACY POLICY | TERMS AND CONDITIONS