Presenter's Name(s)

Libin Liang, UVMFollow

Primary Faculty Mentor Name

Madalina Furis

Status

Graduate

Student College

College of Arts and Sciences

Program/Major

Materials Science

Primary Research Category

Engineering & Physical Sciences

Presentation Title

Relative orientation and strength of exciton states arise from molecular long range ordering in crystalline organic thin film

Time

9:00 AM

Location

Silver Maple Ballroom - Engineering & Physical Sciences

Abstract

Relative orientation and strength of exciton states arise from molecular long range ordering in crystalline organic thin film

Phthalocyanines (Pc’s) are cost-effective and flexible electronics alternative for certain traditional silicon-based semiconductor applications such as field-effect transistors and photovoltaic devices. They could exhibit high mobilities and long-range interactions due to the π-orbital overlap and are great potential for the development of novel electronic and photonic devices. In our study, long range ordered thin films with macroscopic grain sizes and disordered thin films containing 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (H2OBPc) small molecules were prepared with solution-based process pen writing and spin coating, respectively. Oscillation strength and in-plane orientation of electron states within single grains were resolved with absorption and linear dichroism (LD) scanning. The splitting of peaks associated with the HOMO-LUMO bandgap are blue-shifted from disordered sample (705 nm and 750 nm) to ordered thin film (695nm and 750 nm). Additional exciton states (between 750 nm and 890 nm) in the bandgap arise due to the long-range interactions between molecules along the stacking axis and their peak energies were located cooperated with magnetic circular dichroism spectrum. K-vector-resolved absorption and LD scanning were conducted to measure the out-of-plane relative orientation and magnitude of these dipole moments by rotating the sample holder stage. The effect of small strain on the exciton states were also investigated by appalling uniaxial stress along/across molecule stacking axis of ordered thin films on flexible substrate. It is observed that the main peak in the absorption spectrum undergoes a blue-shifted from 855 nm to 850 nm and 16% decrease of the strength with 0.75% applying stain.

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Relative orientation and strength of exciton states arise from molecular long range ordering in crystalline organic thin film

Relative orientation and strength of exciton states arise from molecular long range ordering in crystalline organic thin film

Phthalocyanines (Pc’s) are cost-effective and flexible electronics alternative for certain traditional silicon-based semiconductor applications such as field-effect transistors and photovoltaic devices. They could exhibit high mobilities and long-range interactions due to the π-orbital overlap and are great potential for the development of novel electronic and photonic devices. In our study, long range ordered thin films with macroscopic grain sizes and disordered thin films containing 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (H2OBPc) small molecules were prepared with solution-based process pen writing and spin coating, respectively. Oscillation strength and in-plane orientation of electron states within single grains were resolved with absorption and linear dichroism (LD) scanning. The splitting of peaks associated with the HOMO-LUMO bandgap are blue-shifted from disordered sample (705 nm and 750 nm) to ordered thin film (695nm and 750 nm). Additional exciton states (between 750 nm and 890 nm) in the bandgap arise due to the long-range interactions between molecules along the stacking axis and their peak energies were located cooperated with magnetic circular dichroism spectrum. K-vector-resolved absorption and LD scanning were conducted to measure the out-of-plane relative orientation and magnitude of these dipole moments by rotating the sample holder stage. The effect of small strain on the exciton states were also investigated by appalling uniaxial stress along/across molecule stacking axis of ordered thin films on flexible substrate. It is observed that the main peak in the absorption spectrum undergoes a blue-shifted from 855 nm to 850 nm and 16% decrease of the strength with 0.75% applying stain.