On the use of a bias-light correction for trapping effects in photoconductance-based lifetime measurements of silicon

Abstract

The effectiveness of a method for analytically reducing the effect of trapping centers on photoconductance-based recombination lifetime measurements in silicon is examined. The correction method involves the use of a ''bias-light'' term to subtract out the underlying photoconductance due to the traps. The technique extends, by approximately an order of magnitude, the range of carrier densities over which reasonably accurate ͑within 30%͒ measurements of the recombination lifetime can be made. Guidelines for determining which bias-light intensity will produce the best correction for solar grade multicrystalline silicon wafers, and the range over which it is valid, are developed for several practical cases.

Phosphorous gettering in acidic textured multicrystalline solar cells

“…At a low injection level all the samples except the reference R show high apparent lifetime. This is attributed to an artifact in the measurement when the samples have high density of traps, which is common in mc-Si wafers [7]. This trapping effect is not observed in the reference sample.…”

Influence of crucible and coating quality on the properties of multicrystalline silicon for solar cells

“…Samples from the solidified ingots were taken for oxygen measurements by the Fourier transform infrared (FTIR) spectroscopy and lifetime measurements by the quasi-steady-state photoconductance (QSSPC) [4,5]. Blocks with dimensions 50 Â 50 mm 2 were cut close to the center of RTU1 and Reference 1 ingots for further cell processing.…”

Photoconductors for Measuring Speckle Motion to Monitor Ultrasonic Vibrations

“…The presence of traps in silicon and SOI that affect carrier lifetimes is well noted (MacDonald, 2001;Celler, 2003). Some trapping behavior can increase the effective lifetime of charge carriers; for instance, the presence of shallow traps in effective thermal equilibrium with the conduction band.…”

“…The peaking phenomenon at some bias voltage and the reduction in gain at high illumination levels can be understood in the context of carrier traps within the photoconductor crystal (Rose, 1958;Macdonald, 2001). The presence of traps in silicon and SOI that affect carrier lifetimes is well noted (MacDonald, 2001;Celler, 2003).…”

“…Another trap-related phenomenon that can contribute to the apparent long carrier-lifetimes is electron-hole separation due to the trapping of one of the charge carriers (MacDonald, 2001). For example, if holes are trapped in a state where electrons cannot recombine with them, a corresponding excess of free electrons will build up and contribute to the photoconductance (even if the holes do not contribute to the photoconductance).…”