A ZnO/N-doped carbon nanotube nanocomposite charge transport layer for high performance optoelectronics
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- A ZnO/N-doped carbon nanotube nanocomposite charge transport layer for high performance optoelectronics
- Park, Ji Sun; Lee, Ju Min; Hwang, Sun Kak; Lee, Sun Hwa; Lee, Hyun-Jung; Lee, Bo Ram; Park, Hyung Il; Kim, Ji-Seon; Yoo, Seunghyup; Song, Myoung Hoon; Kim, Sang Ouk
- Band gap energy; Charge transport layer; Charge transport materials; Chemically doped; Device performance; Effective charge; Electrical conductivity; Electron hole; Electron transport layers; Electron-deficient; Electron-rich; Inherent limitations; Interfacial charge; Maximum luminance; Metal oxides; N-doped; Optical transparency; Organic optoelectronics; Processability; Pure ZnO; Solution processable; Transport enhancements; Transport layers; Wide band gap; ZnO
- Issue Date
- ROYAL SOC CHEMISTRY
- JOURNAL OF MATERIALS CHEMISTRY, v.22, no.25, pp.12695 - 12700
- Metal oxide charge transport layers are widely used to promote the interfacial charge transport of organic optoelectronics. Nevertheless, frequently used wide-bandgap metal oxides with low electrical conductivities reveal inherent limitations in the charge transport enhancement. We present the remarkable electro-conductivity enhancement of solution processable ZnO charge transport layers upon dispersing a tiny amount (less than 0.1 wt%) of chemically doped CNTs and the corresponding device performance improvement of light-emitting diodes (OLEDs). Using various undoped or doped CNTs, whose work function was systematically tuned by substitutional doping of electron deficient B or electron rich N,N-doped CNT (N-CNT), the composite showed a lowered work function matching well with the conduction band of ZnO. Consequently, the ZnO/N-CNT nanocomposite transport layer with 0.08 wt% N-CNT showed a five-fold enhancement of electron mobility, while maintaining the intrinsic bandgap energy levels, optical transparency and solution processability of pure ZnO. The inverted OLEDs employing ZnO/N-CNT nanocomposite electron transport layers could facilitate well-balanced electron-hole injection and, thus, more than two-fold enhancement of maximum luminance (from 21 000 cd m(-2) at 14.6 V to 46 100 cd m(-2) at 14.0 V) and efficiency (from 6.9 cd A(-1) at 13.4 V to 14.3 cd A(-1) at 13.6 V). This highly effective charge mobility enhancement enabled by work function tunable, chemically doped CNTs would be beneficial for various organic and inorganic charge transport materials with different energy levels.
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