Luminescent zinc(ii) and copper(i) complexes for high-performance solution-processed monochromic and white organic light-emitting devices

Gang Cheng; Gary Kwok-Ming So; Wai-Pong To; Yong Chen; Chi-Chung Kwok; Chensheng Ma; Xiangguo Guan; Xiaoyong Chang; Wai-Ming Kwok; Chi-Ming Che

doi:10.1039/c4sc03161j

Luminescent zinc(ii) and copper(i) complexes for high-performance solution-processed monochromic and white organic light-emitting devices

Chem Sci. 2015 Aug 1;6(8):4623-4635. doi: 10.1039/c4sc03161j. Epub 2015 Jun 2.

Authors

Gang Cheng^{1

2

3}, Gary Kwok-Ming So¹, Wai-Pong To¹, Yong Chen⁴, Chi-Chung Kwok^{1

2}, Chensheng Ma^{1

5}, Xiangguo Guan¹, Xiaoyong Chang¹, Wai-Ming Kwok⁶, Chi-Ming Che^{1

2}

Affiliations

¹ State Key Laboratory of Synthetic Chemistry , HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry , The University of Hong Kong , Pokfulam Road , Hong Kong SAR , China . Email: cmche@hku.hk.
² HKU Shenzhen Institute of Research and Innovation , Shenzhen 518053 , China.
³ State Key Laboratory on Integrated Optoelectronics , College of Electronic Science and Engineering , Jilin University , Changchun 130012 , China.
⁴ Key Laboratory of Photochemical Conversion and Optoelectronic Materials , Technical Institute of Physics and Chemistry , Chinese Academy of Sciences , Beijing 100190 , China.
⁵ School of Chemistry and Chemical Engineering , Shenzhen University , Shenzhen 518060 , China.
⁶ Department of Applied Biology and Chemical Technology , The Hong Kong Polytechnic University , Hung Hom, Kowloon , Hong Kong SAR , China.

Abstract

The synthesis and spectroscopic properties of luminescent tetranuclear zinc(ii) complexes of substituted 7-azaindoles and a series of luminescent copper(i) complexes containing 7,8-bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate ligand are described. These complexes are stable towards air and moisture. Thin film samples of the luminescent copper(i) complexes in 2,6-dicarbazolo-1,5-pyridine and zinc(ii) complexes in poly(methyl methacrylate) showed emission quantum yields of up to 0.60 (for Cu-3) and 0.96 (for Zn-1), respectively. Their photophysical properties were examined by ultrafast time-resolved emission spectroscopy, temperature dependent emission lifetime measurements and density functional theory calculations. Monochromic blue and orange solution-processed OLEDs with these Zn(ii) and Cu(i) complexes as light-emitting dopants have been fabricated, respectively. Maximum external quantum efficiency (EQE) of 5.55% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.16, 0.19) were accomplished with the optimized Zn-1-OLED while these values were, respectively 15.64% and (0.48, 0.51) for the optimized Cu-3-OLED. Solution-processed white OLEDs having maximum EQE of 6.88%, CIE coordinates of (0.42, 0.44), and colour rendering index of 81 were fabricated by using these luminescent Zn(ii) and Cu(i) complexes as blue and orange light-emitting dopant materials, respectively.