Controlling Morphology and Aggregation in Semiconducting Polymers: The Role of Solvents on Lasing Emission in Poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene

Minghuan Liu,Quanquan Mu,Zenghui Peng,Ji Ma,Chengliang Yang,Zhaoliang Cao,Yonggang Liu,Li Xuan

doi:10.3390/ma10070706

Abstract

Systematic experiments were performed to investigate solvent-dependent morphology and aggregation of the semiconducting polymer film poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV), which was span-cast from nonaromatic strong polarity solvents tetrahydrofuran (THF), trichloromethane (TCM) and aromatic weak polarity solvents chlorobenzene (CB), toluene, and p-xylene. The results indicated that the conformation of the spin-cast MEH-PPV films with weak aggregation such as THF and TCM demonstrated excellent lasing emission performances because of inhibiting the fluorescence quenching induced by bi-molecule process. The Atomic Force Microscope (AFM) images confirmed the distinct morphologies of the spin-cast MEH-PPV films. The amplified spontaneous emission (ASE) was investigated in a simple asymmetric slab planar waveguide structure by methods of variable stripe length (VSL) and shifting excitation stripe (SES). The amplified spontaneous emission (ASE) experiments confirmed the distinct polymer chain conformation. The conformation, which preserved from the spin-cast process, indicated the distinct interactions between solvents and MEH-PPV polymer chains. The pure film spectra were performed to confirm the effect of distinct conformation on the material energy level. This work provides insights into the morphology and aggregation effect of the spin-cast polymer films on the performances of lasers.

Highlights

Organic solid-state lasers (OSSLs) have attracted more attention recently [1,2,3]
The morphology and aggregation was systematically investigated for the lasing emission of semiconducting polymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene]
The morphology and aggregation was systematically investigated for the lasing emission of semiconducting polymer poly[2-methoxy-5-(20 -ethyl-hexyloxy)-1,4-phenylene-vinylene]

Summary

Introduction

Organic solid-state lasers (OSSLs) have attracted more attention recently [1,2,3]. Many materials and device configurations has been developed in this area. Semiconducting materials like semiconducting polymers are promising due to high efficiency, wide spectral coverage, and solution-based processing [4,5]. There have been no demonstrations of commercial devices under electrical injection using semiconducting polymers as active materials, largely because the presence of both injected polarons and metal electrodes quenches the luminescence and raises the threshold [1]. The indirect electrical pumping using inexpensive light emitting diode (LED) is feasible [6].

Methods

Results

Conclusion