Photoluminescence and electroluminescence in polymer mixture of poly(alkylphenylacetylene) and poly(diphenylacetylene) derivatives

Photoluminescence (PL) and electroluminescence (EL) in polymer mixture of blue emissive poly(1-hexyl-2-phenylacetylene) (PHxPA) and green emissive paly(1-phenyl-2-p-n-butylphenylacetylene) (PDPA-nBu) were studied. Both PL and EL in the polymer mixture change from blue to green by the addition of a small amount of PDPA-nBu into PHxPA. This fact has been interpreted as a result of energy transfer from the larger band eap PHxPA to the smaller band gap PDPA-nBu. PL and EL in the polymer mixture are found to be deconvoluted into PL1 and PL2 peaks originating from PDPA-nBu and PHxPA, respectively. PL1 of PDPA-nBu shifts to a higher energy upon introduction of PHxPA, while PL2 of PHxPA also shifts to a higher energy by adding a small amount of PDPA-nBu. From this change in luminescence, molecular conformation at the excited state in the mixture is interpreted to be distorted, depending on the molar ratio of PDPA-nBu and PHxPA. A similar change in PL and EL spectra with molar ratio implies that in this mixture the energy relaxation process is nearly the same for both the cases and does not strongly depend on whether the excited state is produced by photoexcitation or charge injection.