Study of electron-irradiated silicon thin films using transient photocurrent spectroscopy

Electron irradiation of silicon thin films creates localised states, which degrade their opto-electronic properties. We present a series of transient photocurrent spectroscopy (TPC) measurements on electron-irradiated amorphous and microcrystalline silicon films, annealed at progressively increasing temperatures. This has enabled localised states associated with both dangling bonds and conduction band tails to be examined over a wide energy range. Trends in the evolution of the DOS following electron irradiation followed by isochronal annealing steps indicate reductions in the deep defect density, which correlate with spin density. We also find a steepening of the conduction band tail slope in amorphous silicon on annealing. Both defect density and tail slope may be restored close to as-prepared material values. Earlier CPM data are re-examined, and a similar trend in the valence band tail slope is indicated. Computer simulations predict that following e-irradiation changes in deep defect density primarily control solar cell performance, and will tend to obscure effects related to band tails.

[1]  V. Smirnov,et al.  Relationship between absorber layer defect density and performance of a-Si:H and µc-Si:H solar cells studied over a wide range of defect densities generated by 2MeV electron bombardment , 2014 .

[2]  Reinhard Carius,et al.  Structural Order and Staebler–Wronski Effect in Hydrogenated Amorphous Silicon Films and Solar Cells , 2014, IEEE Journal of Photovoltaics.

[3]  V. Smirnov,et al.  Performance of p- and n-side illuminated microcrystalline silicon solar cells following 2 MeV electron bombardment , 2012 .

[4]  V. Smirnov,et al.  Properties of thin-film silicon solar cells at very high irradiance , 2012 .

[5]  V. Smirnov,et al.  Variation of the defect density in a-Si:H and μc-Si:H based solar cells with 2 MeV electron bombardment , 2012 .

[6]  V. Smirnov,et al.  Variation in Absorber Layer Defect Density in Amorphous and Microcrystalline Silicon Thin Film Solar Cells with 2 MeV Electron Bombardment , 2012 .

[7]  A. Curioni,et al.  Large-scale simulations of a-Si:H: the origin of midgap states revisited. , 2011, Physical review letters.

[8]  F. Finger,et al.  Silicon Thin Film Powder Samples for Electron Spin Resonance Investigation: Role of Substrate and Preparation Procedure , 2011 .

[9]  J. R. Srour,et al.  Radiation Effects and Annealing Studies on Amorphous Silicon Solar Cells , 2009, IEEE Transactions on Nuclear Science.

[10]  Reinhard Carius,et al.  Improved homogeneity of microcrystalline absorber layer in thin-film silicon tandem solar cells , 2009 .

[11]  F. Finger,et al.  Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon , 2009 .

[12]  Yadong Jiang,et al.  Effects of irradiation with electrons of different energies on the dark conductivity and the network of hydrogenated amorphous silicon films , 2008 .

[13]  R. Swaaij,et al.  Comparison of amorphous silicon solar cell performance following light and high-energy electron-beam induced degradation , 2008 .

[14]  F. Finger,et al.  Spin Density in Thin Film Silicon Before and After Electron Bombardment , 2007 .

[15]  Arvind Shah,et al.  Proton-induced degradation of thin-film microcrystalline silicon solar cells , 2006 .

[16]  S. Guha,et al.  Hole-mobility limit of amorphous silicon solar cells , 2006 .

[17]  I. Taha,et al.  Infiltration and Coating of Rapid Prototyping Parts , 2005 .

[18]  Arvind Shah,et al.  Thin film silicon solar cells for space applications: Study of proton irradiation and thermal annealing effects on the characteristics of solar cells and individual layers , 2003 .

[19]  P. Tzanetakis.  Metastable volume changes of hydrogenated amorphous silicon and silicon–germanium alloys produced by exposure to light , 2003 .

[20]  M. Mehring,et al.  Defects and transport properties of electron-irradiated microcrystalline silicon with successive annealing , 2003 .

[21]  M. Mehring,et al.  Transport and electrically detected electron spin resonance of microcrystalline silicon before and after electron irradiation , 2002 .

[22]  C. Main.  Interpretation of photocurrent transients in amorphous semiconductors , 2002 .

[23]  C. Longeaud,et al.  Influence of light-soaking and annealing on the microstructure of a-Si:H deposited at 423 K , 2002 .

[24]  M. Mehring,et al.  Influence of electron irradiation on the electronic properties of microcrystalline silicon , 2001 .

[25]  Markus Schubert,et al.  Low-temperature deposition of amorphous silicon solar cells , 2001 .

[26]  F. Houzé,et al.  Electronic and topographic properties of amorphous and microcrystalline silicon thin films , 2001 .

[27]  C. Longeaud,et al.  Evolution with light soaking of the conduction band tail of amorphous-silicon-like materials , 2000 .

[28]  S. Z. Weisz,et al.  The effect of light soaking on the structural order in a-Si:H , 2000 .

[29]  T. Gotoh,et al.  The light-induced metastable lattice expansion in hydrogenated amorphous silicon , 2000 .

[30]  S. Reynolds,et al.  An experimental evaluation of transient and modulated photocurrent density-of-states spectroscopies , 2000 .

[31]  J. R. Srour,et al.  Damage mechanisms in radiation-tolerant amorphous silicon solar cells , 1998 .

[32]  C. Main.  Determination of the Density of States in Semiconductors from Transient Photoconductivity , 1997 .

[33]  P. Danesh,et al.  Correlations between structural and optoelectronic properties of a-Si:H grown by homogeneous chemical vapor deposition , 1996 .

[34]  Brandt,et al.  Pulsed-light soaking of hydrogenated amorphous silicon. , 1994, Physical review. B, Condensed matter.

[35]  K. Pierz,et al.  Subbandgap absorption in a-Si:H from photoconductivity spectra☆ , 1985 .

[36]  Tsai,et al.  Light-induced metastable defects in hydrogenated amorphous silicon: A systematic study. , 1985, Physical review. B, Condensed matter.

[37]  Benjamin Abeles,et al.  Evidence for Exponential Band Tails in Amorphous Silicon Hydride , 1981 .