Spectral sensitivity dependence on the details of preparation for P3HT:PCBM bulk heterojunction solar cells

The performance of bulk heterojunction P3HT :PCBM polymer solar cells is studied using current-voltage and spectral sensitivity measurements. Front transparent contacts of either ITO or a sputtered multilayer TiO₂/Ag/TiO₂ transparent conductive electrode are applied. Thin PEDOT:PSS and P3HT:PCBM polymer layers are deposited on these substrates by spin coating. The degradation of the solar cells is studied by subjecting them to UV irradiation. The obtained spectral sensitivity curves are analyzed in comparison with the optical absorption spectra of the transparent electrodes and active layers employed. It is observed that there is a pronounced dependence of the spectral sensitivity curves on the thermal treatment and UV irradiation applied to the solar cells. The performance of the multilayer TiO₂/Ag/TiO₂ transparent conductive electrodes is also studied in comparison with that of the ITO ones