Interface energetics of polyfluorene and fluorene-arylamine copolymers

Jaehyung Hwang; Antoine Kahn

doi:10.1117/12.684787

5 December 2006 Interface energetics of polyfluorene and fluorene-arylamine copolymers

Jaehyung Hwang, Antoine Kahn

Proceedings Volume 6333, Organic Light Emitting Materials and Devices X; 633310 (2006) https://doi.org/10.1117/12.684787
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

Abstract

The energy level alignment at interfaces between poly(9,9'-dioctylfluorene) (F8), poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-diphenylamine) (TFB) and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) and substrates with work function ranging from 4.3 eV to 5.1 eV is investigated via ultra-violet photoemission spectroscopy. Vacuum level alignment with flat bands away from the interface is found when the interface hole barrier is 0.6 eV or larger. Band bending that moves the filled states away from the Fermi level occurs when the hole barrier is smaller than 0.4 eV. This is presumably due to the accumulation of excess interface charges on the polymer side when the interfacial barrier is small. The resulting field shifts the polymer levels in a way that limits charge penetration in the bulk of the film. We also study metal-on-polymer interfaces. Different metals exhibit different growth modes. While Pt shows complete layer-by-layer type of growth, Al shows island type of growth. Current-voltage measurement shows the presence of hole traps in the Au-on top-contact device, suggesting diffusion of small Au clusters into the polymer film. Furthermore, metal-on-polymer interfaces frequently present different interface energetics than their polymer-on-metal counterpart. e.g. a 0.3 - 0.4 eV higher hole injection barrier for Pt-on-TFB than TFB on Pt.

Citation Download Citation

Jaehyung Hwang and Antoine Kahn "Interface energetics of polyfluorene and fluorene-arylamine copolymers", Proc. SPIE 6333, Organic Light Emitting Materials and Devices X, 633310 (5 December 2006); https://doi.org/10.1117/12.684787

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available