Minority‐carrier diffusion lengths in GaAs at 298 K were determined in Ge‐doped p‐type layers and Sn‐doped n‐type layers by short‐circuit photocurrent measurements. The layers were grown by liquid‐phase epitaxy and utilized a 1‐ to 2‐μ top layer of Al0.5Ga0.5As to eliminate surface recombination. Electron diffusion lengths Ln of 7–8 μ were obtained at concentrations less than 1×1018 holes/cm3 with a decrease to 0.8 μ at 1×1019 holes/cm3. Hole diffusion lengths Lp of 2–4μ were obtained at concentrations less than 1×1018 electrons/cm3 with a decrease to 0.3 μ at 6×1018 electrons/cm3. The relatively constant diffusion length in p‐ and n‐type layers below concentrations of 1×1018 cm−3 is determined by nonradiative recombination. At hole concentrations above 1×1018 cm−3, the radiative recombination contributes to the decrease in Ln. For the n‐type layers, the rapid decrease in Lp above concentrations of 1×1018 cm−3 results from an increase of nonradiative recombination at high donor concentrations.

Variation of minority-carrier diffusion length with carrier concentration in GaAs liquid-phase epitaxial layers

A new look at silicon solar cell performance

Low-high junction theory applied to solar cells

Abstract The performance of GaAs solar cells has been calculated as a function of the doping levels, using practical values for the transport parameters. Calculations show that surface recombination is a more probable cause than recombination in the junction region of the poor efficiencies obtained in practice. Electric fields built into the cell by doping gradations may be used to reduce surface losses and produce an efficiency exceeding 20 per cent for a surface recombination velocity of 10 6 cm/sec. This figure allows for the finite resistance of the surface layer, the effect of which is considered in detail for several cases. Results for Si cells are also presented. These are well in accord with the values obtained in practice. For both materials consideration is given to the degradation brought about by particle bombardment.

Calculated efficiencies of practical GaAs and Si solar cells including the effect of built-in electric fields. Technical report

The performance of GaAs solar cells has been calculated as a function of the doping levels, using practical values for the transport parameters Calculations show that surface recombination is a more probable cause than recombination in the junction region of the poor efficiencies obtained in practice Electric fields built into the cell by doping gradations may be used to reduce surface losses and produce an efficiency exceeding 20 per cent for a surface recombination velocity of 10 6 cm/sec This figure allows for the finite resistance of the surface layer, the effect of which is considered in detail for several cases Results for Si cells are also presented These are well in accord with the values obtained in practice For both materials consideration is given to the degradation brought about by particle bombardment

Calculated efficiencies of practical GaAs and Si solar cells including the effect of built-in electric fields

The collection efficiency in solar cells is trealed by a new method in which all the effects of the solar spectrum and the absorption curve are contained in a single funetion readily obtained by numerical integration. The method is illustrated by a detailed study of the effects of surface recombination, body recombination and junction depth in silicon cells. The method is also generalized to include built-in electric fields, and calc Illations are given for silicon. Sufficiently strong fields 10 improve the collection efficiency markedly can be produced in some compollnd semiconductors from a gradient in the energy gap. A disclLssion is given of the dependence of the collection efficiency on the absorption curve of the semiconductor. It is shown that silicon has a very favorable absorption curve in camparison with GaAs or InP. Finally, a treatment is given of the minority carrier collection in a two-Junction cell, and calculations arc presented for silicon. It is concluded that this structure may be important for cells with high energy gaps and short lifetimes.

http://ieeexplore.ieee.org/iel7/6731005/6773657/06773661.pdf

D. A. Kleinman

Papers

Considerations on the solar cell