Light induced fluorescence enhancement in MEH-PPV thin films

Laser treatment of MEH-PPV films increased photoluminescence (PL) by up to 400% in nitrogen. Maximum enhancement was observed with irradiances between 20 and 70 μW/μm2, and a total fluence of ~700 μJ/μm2. (Below ~1 μW/μm2 only photobleaching was observed). PL continued to increase for 16 h after treatment ended suggesting that the morphology continued to evolve in the absence of light. After 1 day, emission remained unchanged suggesting the new morphology is stable at room temperature. We believe this increased PL efficiency in primarily the result of reduced efficiency of trap-assisted recombination due to decreased interchain energy transfer.