Controlled chain stiffness to reduce the non-radiative decay rate in MEH-PPV intra-chain emissive species

Jui-Hung Hsu^1*, Jonathan David White², Arnold Chang-Mou Yang³

¹Department of Materials and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung, Taiwan
²Department of Electrical Engineering, Yuan-Ze University, Yaoyuan, Taiwan
³Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Jui-Hung Hsu, email:jhsu@mail.nsysu.edu.tw

The effect of controlled chain stiffness by unidirectional tensile stress on the emission properties of poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] MEH-PPV polymers was investigated. Polarization microscopy indicated that the large tensile stresses align MEH-PPV chains parallel to the stress. Fluorescence lifetime imaging microscopy (FLIM) measurements indicated that fluorescence lifetime of the stressed polymers increased ~40% to approximately that of the pristine polymer. The photoluminescence spectra were independent of stress suggesting that this increase is not due to changes in radiative decay rates but primarily due to the suppression of non-radiative decay channels. This resulted in a room temperature fluorescence quantum yield of almost 100%. We believe such highly stressed aligned polymer chains may reinforce the chain stiffness, and strongly reduce the influence of the inherent defects and quenchers.

Keywords: fluorescence lifetime imaging microscopy, fluorescence yield, MEH-PPV, tensile stress