Enhancing device efficiencies of solid-state white light-emitting electrochemical cells by employing waveguide coupling

Chia Yu Cheng, Chi Wei Wang, Jing Rong Cheng, Hsiao Fan Chen, Yun Shiuan Yeh, Hai-Ching Su*, Chih Hao Chang, Ken Tsung Wong

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Solid-state white light-emitting electrochemical cells (LECs) have received intense scientific attention owing to their potential applications in display and lighting. Although device efficiencies of white LECs have been significantly improved in recent years, further improvements are still required for their practical applications. In this work, we demonstrate the enhancement of device efficiencies of white LECs by employing waveguide coupling. Two transparent photoresist (TPR) layers doped with TiO2 nanoparticles (NPs) are inserted between the indium tin oxide (ITO) layer and the glass substrate. By tuning the doping concentration of 25 nm TiO2 NPs in the upper TPR layer to adjust the refractive index, effective waveguide coupling between the ITO layer and the lower TPR layer can be achieved. Since the lower TPR layer contains 250 nm TiO2 NPs, electroluminescence (EL) outcoupled from the ITO layer can be scattered and redirected into the forward direction. Furthermore, the EL trapped in the glass substrate can also transmit into the lower TPR layer and then is scattered to the forward direction. When the EL trapped in the ITO layer and the glass substrate can be effectively recycled into the forward direction, the peak external quantum efficiency and power efficiency obtained in white LECs employing waveguide coupling are up to 19.4% and 34.1 lm W-1, respectively. These efficiencies are among the highest reported for white LECs and thus confirm that waveguide coupling would be useful for realizing highly efficient white LECs. In addition to the enhanced device efficiencies, improved color migration of EL spectra, which is desired for lighting applications, can be obtained in white LECs with scattering waveguide layers since EL of different angles can be mixed in the forward direction.

Original languageEnglish
Pages (from-to)5665-5673
Number of pages9
JournalJournal of Materials Chemistry C
Issue number22
StatePublished - 14 Jun 2015


Dive into the research topics of 'Enhancing device efficiencies of solid-state white light-emitting electrochemical cells by employing waveguide coupling'. Together they form a unique fingerprint.

Cite this