Variations in spectral response behaviour in single layer organic solar cells with active layer thickness and bias

The spectral response is a valuable tool for understanding the photovoltaic response and the device operation of a solar cell. In this paper, the antibatic and symbatic spectral response behaviour of a single layer poly(3-hexylthiophene-2, 5-diyl) (P3HT) solar cell to its absorption spectrum is investigated. The reasons for shift in the nature of the spectral response for change in active layer thickness or bias across device has been examined using an electro-optical model based on the transfer matrix method. The relative value of the charge transport efficiencies for different bias conditions have been evaluated and their variation with the applied bias have been explained with the help of the theory discussed in this paper. The spectral response analysis discussed gives an insight about the role of transport of photo generated charge carriers in shaping the spectral response of single layer organic solar cells.