The effect of i‐layer thickness, tin oxide texture, and back reflector (BR) on optical enhancement has been systematically studied in a series of 20 a‐Si p–i–n solar cells. The internal quantum efficiency has been analyzed by a simple model based on the work of Schade and Smith. The enhancement of optical absorption is characterized by m, a wavelength‐dependent fitting parameter representing the increase in optical pathlength relative to the i‐layer thickness d. Solar cells with an Al BR have negligible optical enhancement, with m < 1.5, consistent with large parasitic absorption at the Al/Si interface as reported by others. Solar cells on highly textured SnO2 with ZnO/Al or ZnO/Ag BR have peak values of m ∼ 3–4, with ZnO/Ag having slightly larger values than ZnO/Al. It was found that m has a strong dependence on the product αd, and that maximum values of m increase with reflectivity of the BR. It is shown that a major source of parasitic absorption loss at long wavelengths is light trapping in the textured SnO2 front contact. Copyright © 2002 John Wiley & Sons, Ltd.

Ab!;tract In-quadrature freqiency-resolved photocurrent (PRPC) measurements were perforined on amorphous SeTe films between 20 K and 290 K. and as a function of excitation intensity. These measuremenrs yield lifetime distributions directly. The results show that the reclimbination kkes place between distant pain and that there is a continuous distribution of stat!s within the mobility gap.

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In-quadrature frequency-resolved photocurrent (FRPC) measurements were performed on amorphous (a-) As 2 Te 3 thin films between 20 K and 290 K, and as a function of excitation intensity. These measurements yield lifetime distributions directly. We have obtained a recombination lifetime of about 8 µs for a-As 2 Te 3 . This lifetime was found to be independent of excitation intensity and temperature. It is explained in terms of the capture of nonequilibrium carriers. We also present the temperature and intensity dependences of the FRPC response of a-As 2 Te 3 at a constant modulation frequency. They give information about recombination kinetics.

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A new method has been developed to characterize the TCOlp contact in a-Si p-i-n superstrate solar cells and modules. The method is applied to a series of devices fabricated at BP Solar on commercial SnO, and ZnO-coated SnO, having different p-layer recipes and pre-deposition treatments. Values of the contact resistance (R, ) of lf0.5 !2-cm2 were found for a wide range of TCO and p-layer processing including ZnO. Temperature dependence of R, gave barrier height of 40-55 meV. Analysis of devices with a thin ZnO layer on SnO, and with different predeposition treatments indicates lower V, , and FF observed with ZnO is not due to the contact but to changes in the p/i junction recombination. The solar cell performance is very sensitive to the ZnO surface treatment but R, is not.No evidence was found for a blocking or high resistance ZnO/p contact.

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