Ordered Polymer Nanofibers Enhance Output Brightness in Bilayer Light-Emitting Field-Effect Transistors

Polymer light emitting field effect transistors are a class of light emitting devices that reveal interesting device physics.Device performance can be directly correlated to the most fundamental polymer science. Control over surface properties of the transistor dielectric can dramatically change the polymer morphology, introducing ordered phase. Electronic properties such as carrier mobility and injection efficiency on the interface can be promoted by ordered nanofibers in the polymer. Moreover, by controlling space charge in the polymer interface, the recombination zone can be spatially extended and thereby enhance the optical output.




Figure 1. (a) Photo of the operating device; (b) schematic of the device architecture; (c) molecular structures of PFN+BIm4- CPE, Super Yellow, and PATBT

The physical structure between the transistors and the passivated dielectric provides energetic preference on the surface, guides semiconducting polymers and forms ordered polymer fibers. Order in the PATBT (poly(3,6-dialkylthieno[3,2-b]thiophene-co-bithiophene)) raises carrier mobility and injects more holes into the luminescent SY layer. More holes accumulate because of the energy barrier introduced by the CPE at the drain electrode, therefore, holes distribute into a wider region in SY. While the current density increases, the recombination zone width simultaneously increases and emits more photons. To improve the efficiency, asymmetric contacts are foreseen as a next step. We expect that still higher brightness and efficiency should be achievable from bilayer LEFETs with asymmetric contacts.

Referencia:
Ordered Polymer Nanofibers Enhance Output Brightness in Bilayer Light-Emitting Field-Effect Transistors
Ben B.Y. Hsu, Jason Seifter, Christopher J. Takacs, Chengmei Zhong, Hsin-Rong Tseng, Ifor D. W. Samuel, Ebinazar B. Namdas, Guillermo C. Bazan, Fei, Huang, Yong Cao, and Alan J. Heeger
ACS Nano 2013 7 (3), 2344-2351