Simultaneous enhancement of electron injection and air stability in N-type organic field-effect transistors by water-soluble polyfluorene interlayers.
Here, we report the simultaneous attainment of efficient electron injection and enhanced stability under ambient conditions for top-gate/bottom-contact (TG/BC), n-type, organic field-effect transistors (OFETs) using water-soluble polyfluorene derivatives (WPFs). When inserting the WPF interlayers between a semiconductor and the BC Au electrodes, initially the ambipolar (6,6)-phenyl-C61butyric acid methyl ester (PCBM) OFETs were fully converted to unipolar charge transport characteristics that were exclusively n-type with significantly increased electron mobilities as high as 0.12 cm(2)/(V s) and a decreased threshold voltage. These improvements were mostly attributed to the interfacial dipoles of WPF layers that aligned to form a favorable energy band structure for efficient electron injection and to effectively block counter charge carriers. These were confirmed when values for the reduced work function of metal electrodes with WPFs and their correlated contact resistance were measured via the ultraviolet photoemission spectroscopy and the transmission-line method, respectively. Moreover, the WPF interlayers played an important role in air stability of PCBM OFETs that exhibited higher and appreciably enhanced by increasing the ethylene-oxide side chain lengths of WPFs, which presumably was due to the water/oxygen/ion capturing effects in the hydrophilic interlayers.
Heeger Center for Advanced Materials, School of Materials Science and Engineering, Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
Jihong
J
Kim
Dongyoon
D
Khim
Rira
R
Kang
Seung-Hoon
SH
Lee
Kang-Jun
KJ
Baeg
Minji
M
Kang
Yong-Young
YY
Noh
Dong-Yu
DY
Kim