Light source selection for a solar simulator for thermal applications: A review

Solar simulators are used to test components and systems under controlled and repeatable conditions, often in locations with unsuitable insolation for outdoor testing. The growth in renewable energy generation has led to an increased need to develop, manufacture and test components and subsystems for solar thermal, photovoltaic (PV), and concentrating optics for both thermal and electrical solar applications. At the heart of any solar simulator is the light source itself. This paper reviews the light sources available for both low and high-flux solar simulators used for thermal applications. Criteria considered include a comparison of the lamp wavelength spectrum with the solar spectrum, lamp intensity, cost, stability, durability, and any hazards associated with use. Four main lamp types are discussed in detail, namely argon arc, the metal halide, tungsten halogen lamp, and xenon arc lamps. In addition to describing the characteristics of each lamp type, the popularity of usage of each type over time is also indicated. This is followed by guidelines for selecting a suitable lamp, depending on the requirements of the user and the criteria applied for selection. The appropriate international standards are also addressed and discussed. The review shows that metal halide and xenon arc lamps predominate, since both provide a good spectral match to the solar output. The xenon lamp provides a more intense and stable output, but has the disadvantages of being a high-pressure component, requiring infrared filtering, and the need of a more complex and expensive power supply. As a result, many new solar simulators prefer metal halide lamps

Interface Properties of the Amorphous Silicon/Crystalline Silicon Heterojunction photovoltaic cell

Amorphous-crystalline silicon (a-Si:H/c-Si) heterojunctions have the potential of being a very high efficiency silicon photovoltaic platform technology with accompanying cost and energy budget reductions. In this research a heterojunction cell structure based on a-Si:H deposited using a DC saddle field plasma enhanced vapour deposition (DCSF PECVD) technique is studied, and the a-Si:H/c-Si and indium tin oxide/a-Si:H interfaces are examined using several characterization methods.Photocarrier radiometry (PCR) is used for the first time to probe the a-Si:H/c-Si junction. PCR is demonstrated as a carrier lifetime measurement technique - specifically, confirming carrier lifetimes above 1 ms for 1-5 Ohm.cm phosphorous-doped c-Si wafers passivated on both sides with 30 nm of i-a-Si:H. PCR is also used to determine surface recombination velocity and mobility, and to probe recombination at the a-Si:H/c-Si interface, distinguishing interface recombination from recombination within the a-Si:H layer or at the a-Si:H surface.A complementary technique, lateral conductivity is applied over a temperature range of 140 K to 430 K to construct energy band diagrams of a-Si:H/c-Si junctions. Boron doped a-Si:H films on glass are shown to have activation energies of 0.3 to 0.35 eV, tuneable by adjusting the diborane to silane gas ratio during deposition. Heterojunction samples show evidence of a strong hole inversion layer and a valence band offset of approximately 0.4 eV; carrier concentration in the inversion layer is reduced in p-a-Si:H/i-a-Si:H/c-Si structures as intrinsic layer thickness increases, while carrier lifetime is increased.The indium tin oxide/amorphous silicon interface is also examined. Optimal ITO films were prepared with a sheet resistance of 17.3 Ohm/square and AM1.5 averaged transmittance of 92.1%., for a film thickness of approximately 85 nm, using temperatures below 200 degrees celcius. Two different heat treatments are found to cause crystallization of ITO and to change the properties of the underlying a-Si:H film.Finally, an open circuit voltage of 699 mV was achieved using DCSF PECVD in the tetrode configuration to fabricate a metal/ITO/p-a-Si:H/i-a-Si:H/n-c-Si/i-a-Si:H/n+-a-Si:H/metal photovoltaic cell on a texturized wafer. The 4 cm2 cell had an efficiency of 16.5%, a short circuit current of 36.4 mA/cm2 and a fill factor of 64.7%.Ph.D

Calculation and measurement of the band-bending in crystalline silicon as an optimization tool for silicon heterojunction solar cells

International audienc

Influence of the undoped a Si H buffer layer on a Si H c Si heterojunctions from planar conductance and lifetime measurements

International audienceIn highly efficient amorphous silicon/crystalline silicon heterojunction (a-Si:H/c-Si) solar cells, the c-Si wafer is passivated by a nanometer-thin buffer layer, which is undoped amorphous silicon. Here, we report on the systematic measurement of the passivation quality (minority carrier effective lifetime) by photo-conductance decay and of the band bending in c-Si using the planar conductance technique. The thickness of the buffer layers is varied. An analytical model to calculate the band bending in c-Si is presented; it aids in understanding the influence of the buffer layer on the band bending. We find that when the buffer layer thickness increases the passivation quality increases and the band bending decreases. Therefore, we suggest that an optimum has to be found to reach good interface defect passivation and a high band bending

Interface properties of amorphous-crystalline silicon heterojunctions prepared using DC saddle-field PECVD

LGEP 2011 ID = 780International audienc

TEMPERATURE DEPENDENT PHOTOLUMINESCENCE IN SILICON BASED HETEROJUNCTION SOLAR CELL

International audienc