Unveiling the Injection-Dependence of the Diffusion Length Via the Spectral Response of the Voltage of Silicon Solar Cells

The minority carrier diffusion length as a function of carrier density has been extracted from the spectral response of the open-circuit voltage of silicon solar cells, which has been measured with the quasi-steady-state spectral photovoltage technique, QSSV_oc -lambda. The method can determine a relative internal quantum efficiency for a broad range of voltages, and therefore, of carrier injection levels. From the internal quantum efficiency, the diffusion length is derived using standard procedures. High-efficiency solar cells fabricated on p-type multicrystalline silicon of four different resistivities have been used in this investigation. While the analysis of the spectral response of the short-circuit current did not show any injection dependence of the diffusion length, the analysis of the spectral response of the voltage, on the contrary, unveiled that the diffusion length can have a strong dependence on carrier density, even at very low injection levels