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[en] Highlights: • Fluorescence of Rh6G embedded in a 13.5 nm thick polystyrene film is studied. • Lifetime lengthens 3 fold with thickness of an underlying PMMA layer. • Flux decreases with thickness of an underlying PMMA layer. • Rh6G dipoles re-orient perpendicular to the air interface as thickness increases. Bilayer films consisting of the optically transparent polymers, polystyrene (PS) and poly(methyl methacrylate) (PMMA) were spin-cast on glass substrates. The upper 13.5 nm layer (PS) was lightly doped with Rhodamine-6 G (RH6G) or MEH-PPV. While the fluorescence of MEH-PPV was independent of PMMA thickness, the lifetime of RH6G increased 3-fold as the underlying PMMA thickness increased from 0 to 500 nm while the collected flux decreased suggesting a reorientation of the smaller molecule's dipole with respect to the air-polymer interface with PMMA thickness. This suggests lifetime may find application for nondestructive thickness measurements of transparent films with sub-micron lateral resolution and large range.