https://web.njit.edu/~sirenko/PapersNJIT/1-s2.0-S0927024812000931-main.pdf

Temperature dependence of solar cell performance—an analysis

Theoretical efficiencies are calculated for two‐junction, series‐connected solar cells using air mass 1.5 global and direct irradiance spectra. For band‐gap combinations previously limited by a low bottom‐cell current, thinning of the top cell is shown to result in significant increases in the theoretical efficiencies. The increases are primarily due to increased short‐circuit currents, since current matching is achievable. Smaller gains are also seen in the open‐circuit voltages of the thinner cells when a low surface‐recombination velocity is assumed. Thus, a number of material combinations which previously could only be used in four‐terminal configurations can now be considered for series‐connected two‐junction solar cells.

Modeling of two‐junction, series‐connected tandem solar cells using top‐cell thickness as an adjustable parameter

The author begins with an Introduction in which he discusses basic concepts, recent developments, potential advantages offered by TPV systems and a historical background. He then provides a background in blackbody radiators and examines selective and rare-earth oxide radiators. He discusses modelling, fabrication and characterization of TPV convertors, particularly those based on GaSb and InGaAs. He examines the several approaches to recirculating the sub-bandgap photons and ends with a section on modelling of TPV system performance, and conceptual designs and demonstration of TPV systems, including solar powered, biofueled nuclear-fueled, liquid hydrocarbon-fueled, diesel-fueled, propane fueled, and natural gas fueled TPV systems.

A review of progress in thermophotovoltaic generation of electricity

This letter reports the synthesis of indium nitride (InN) nanowires on gold-patterned silicon substrates in a controlled manner using a method involving thermal evaporation of pure indium. The locations of these InN nanowires were controlled by depositing gold in desired areas on the substrates. Scanning electron microscopy and transmission electron microscopy investigations showed that the InN nanowires are single crystals with diameters ranging from 40 to 80 nm, and lengths up to 5 μm. Energy dispersive x-ray spectrometry showed that the ends of the nanowires are composed primarily of Au, and the rest of the nanowires were InN with no detectable Au incorporations. The Raman spectra showed peaks at 445, 489, and 579 cm−1, which are attributed to the A1(transverse optical), E2, and A1(longitudinal optical) phonon modes of the wurtzite InN structure, respectively. Photoluminescence spectra of the InN nanowires showed a strong broad emission peak at 1.85 eV.

Selective-area growth of indium nitride nanowires on gold-patterned Si(100) substrates

Cadmium Telluride Solar Cells

Tandem solar cells can have significantly higher efficiencies than single-junction solar cells because they convert a larger fraction of the incident solar spectrum to electricity. For the design of tandem solar cells the spectral p-n junction model is proposed. It is based on tabulated standard spectra, on the fit of experimentally achieved open-circuit voltages, and assumes a quantum efficiency of unity. By consistent treatment of the energy gap in the diode equation, the model can be quantitatively applied to all tandem solar-cell systems. The special form and use of the reverse saturation current density is discussed in detail. The spectral p-n junction model is rigorously applied based on accepted standard spectra. The tandem solar-cell performance limits based on the model are calculated. A quantitative expression for the increase in efficiency under concentration is derived. Choosing materials with optimum bandgaps, a two-solar-cell two-terminal tandem system can achieve a theoretical maximum efficiency of 38.2-percent (AM1.5 global). A two-solar-cell four-terminal tandem system can have a maximum efficiency of 39.1 percent at the same spectrum. This four-terminal system allows more freedom in choosing the most efficient bandgap combinations. Assuming realistic losses, a configuration consisting of a Si solar cell on the bottom and a solar cell with a bandgap, E g = 1.85 eV on the top, a maximum efficiency of 32.1 percent (AM1.5 global) can be predicted. Increased efficiency can be obtained from a three-solar-cell six-terminal tandem system. With an optimum bandgap combination the theoretical maximum efficiency is 44.5 percent (AM1.5 global) for the three-solar-cell system. The limits predicted by the model are discussed for tabulated standard spectra. The highest achievable efficiency is 57.3 percent (AM1.5 global) without concentration of the incident light. The increase in efficiency under concentration is evaluated, and it is found that the relative change of the efficiency at any concentration X is linear with In (X).

M.E. Nell

Papers

The spectral p-n junction model for tandem solar-cell design