Transport properties are very important for solar cells. The efficiency of solar cells is determined by the
competition of carrier collection and recombination. The most important parameter is the carrier mobility-lifetime
product. However, methods commonly used for measuring transport parameters require specially designed samples.
The results are often not easily correlated to solar cell performance. In this paper, we present our studies of
extraction of material properties from conventional current-voltage characteristics and quantum efficiency curves.
First, we carried out analyses of shunt resistance as a function of the light intensity. For solar cells with no clear
parasitic shunt resistance, the shunt resistance is inversely proportional to the short-circuit current, and its
proportionality coefficient is related to the effective carrier mobility-lifetime product. For an a-Si:H solar cell made
under an optimized condition with high hydrogen dilution, the effective mobility-lifetime product was estimated to
be 1.2x10-8 cm2/V. For a-SiGe:H solar cells, the effective mobility-lifetime product depends on Ge content. For
optimized a-SiGe:H bottom cells used in high efficiency a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structures, their
values are ~5.0x10-9 cm2/V. For high efficiency nc-Si:H solar cells, the effective mobility-lifetime product is
~5.0x10-7 cm2/V. Second, we measured the quantum efficiency as a function of electrical bias and developed an
analytical model to deduce the effective mobility-lifetime product. The results obtained from the second method are
consistent with the values from the first method. We will present detailed analyses and interpretations of the
transport parameters and their correlation to solar cell performance.