Characterization of defects in a-Si:H solar cells using sub-band gap photocurrent spectroscopy

Measurements of sub-band gap primary photocurrent spectra on p-i-n devices are used to characterize defects between 1.0 and 1.4 eV above the valence band. The effect of light soaking is to increase the absorption due to light-induced defects centered between 1.2 and 1.3 eV, consistent with the results from photothermal deflection spectroscopy. A degradation in FF (fill factor) is correlated with an increase in light-induced defects measured on the same solar cells. Although increasing the i-layer deposition temperature reduces FF, it is suggested that this reduction is due to p/i interface degradation because bulk i-layer defects decrease with the deposition temperature. The measurement is applicable to any a-Si:H or a-SiGe:H p-i-n solar cell and provides information about fundamental i-layer properties (defect density and Urbach energy) which can be related to the device performance.<<ETX>>

[1]  K. Mackenzie,et al.  Comparative study of the optical absorption spectra of amorphous hydrogenated silicon derived from photothermal deflection spectroscopy and photoconductivity measurements , 1987 .

[2]  M. Konagai,et al.  High-Performance Hydrogenated Amorphous Silicon-Germanium Solar Cells Fabricated by Photochemical Vapor Deposition , 1987 .

[3]  R. Rocheleau,et al.  Novel photochemical vapor deposition reactor for amorphous silicon solar cell deposition , 1987 .

[4]  S. Wagner,et al.  Photothermal and photoconductive determination of surface and bulk defect densities in amorphous silicon films , 1987 .

[5]  R. Rocheleau,et al.  Density of midgap states and Urbach edge in chemically vapor deposited hydrogenated amorphous silicon films , 1986 .

[6]  H. Okamoto,et al.  Below-gap primary photocurrent associated with correlated defects in hydrogenated amorphous silicon , 1985 .

[7]  Guha,et al.  Determination of the gap-state distribution of hydrogenated amorphous silicon alloys from sub-band-gap absorption measurements. , 1985, Physical Review B (Condensed Matter).

[8]  B. Abeles,et al.  Urbach edge and the density of states in hydrogenated amorphous silicon , 1983 .

[9]  N. Amer,et al.  Energy dependence of the carrier mobility-lifetime product in hydrogenated amorphous silicon , 1983 .

[10]  J. Stuchlík,et al.  Density of the gap states in undoped and doped glow discharge a-Si:H , 1983 .

[11]  R. Crandall.  Photoconductivity and transport in hydrogenated amorphous silicon , 1980 .

[12]  G. Moddel,et al.  Derivation of the low-energy optical-absorption spectra ofa-Si: H from photoconductivity , 1980 .

[13]  R. Crandall.  Band-Tail Absorption in Hydrogenated Amorphous Silicon , 1980 .

[14]  H. Itozaki,et al.  Properties of a-SiGe and Application to Stacked Solar Cell , 1987 .

[15]  K. Rajan,et al.  Light-Induced Degradation and Annealing Behaviour of Amorphous Silicon: A Comparison of Films and Devices , 1987 .

[16]  R. Crandall.  Chapter 8 Photoconductivity , 1984 .