Theoretical and experimental study of photocurrent action spectrum of ITO/sexithiophene/Al structure

We have studied photovoltaic cells using sexithiophene in (ITO/6T/Al) structure, and we have measured the action spectrum obtained by illumination through the aluminum side which is compared to the measured absorption spectrum. Two models were used to interpret this experiment: the Ghosh model using the carriers diffusion property in the bulk, and the kinetic model describing the dynamic behavior of the charge carriers in the device. The confrontation of these models with the experimental spectra allows us to reach the diffusion length of electron–hole pair L=2×10−6 cm. We also give the mobility of carriers (μn≈1.5×10−4 cm2/V s, and μp≈1.5×10−5 cm2/V s) and their diffusion coefficients (Dn≈4×10−6 cm2/s, and Dp≈4×10−7 cm2/s).