A comparative study of Al and LiF:Al interfaces with poly (3-hexylthiophene) using bias dependent photoluminescence technique

The qualitative nature of the interface of poly (3-hexylthiophene) (P3HT) with Aluminum (Al) and LiF modified Aluminum (LiF:Al) has been studied using photoluminescence (PL) spectra. It was observed that coating Al on pristine P3HT film resulted in an increase in the degree of intrachain disorder. Also, a blue shift in the peak PL intensity was observed. These observations have been explained on the basis of intrachain disorder induced by the deposition of Al via thermal evaporation on P3HT film. Furthermore, bias dependence of PL spectra for ITO/P3HT/Al and ITO/P3HT/LiF:Al type Schottky cells were studied. Under the reverse bias conditions, PL quenching was found to relate directly to the depletion layer width. The increase in depletion width was found to be higher in the Al cell as compared to that of the LiF:Al cell. However, the photocurrents were higher in LiF:Al coated cells. These observed results have been explained on the basis of the difference in their respective band alignment.