Effect of interchain coupling on conducting polymer luminescence: excimers in derivatives of poly(phenylene vinylene)

TL;DR

This paper investigates how interchain coupling influences the luminescence of conducting polymer derivatives by analyzing excimer formation and emission shifts, providing quantitative estimates of interchain coupling strengths in specific polymers.

Contribution

It introduces a method to calculate interchain coupling effects on excimer emission and applies it to determine coupling strengths in two polymer derivatives.

Findings

Estimated interchain coupling values: 0.52 eV for CN-PPV and 0.16 eV for MEH-PPV.

Demonstrated how interchain distance affects excimer emission red-shift.

Provided insights into the relationship between polymer structure and luminescence properties.

Abstract

Optical excitation of a chain in a polymer film may result in formation of an excimer, a superposition of on-chain excitons and charge-transfer excitons on the originally excited chain and a neighboring chain. The excimer emission is red-shifted compared to that of an on-chain exciton by an amount depending on the interchain coupling $t_\perp$. Setting up the excimer wavefunction and calculating the red shift, we determine average $t_\perp$ values, referred to a monomer, of 0.52 eV and 0.16 eV for poly(2,5-hexyloxy $p$-phenylene cyanovinylene), CN-PPV, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1, 4 p-phenylene vinylene], MEH-PPV, respectively, and use them to determine the effect of interchain distance on the emission.