Synthetic Metals 161 (2011) 213–218 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Synthesis and characterization of red iridium(III) complexes containing phenothiazine-phenylquinoline based on main ligand for solution-processed phosphorescent organic light-emitting diodes Jin Su Park a , Myungkwan Song a , Yeong-Soon Gal b , Jae Wook Lee c,∗ , Sung-Ho Jin a,∗ a Department of Chemistry Education, Interdisciplinary Program of Advanced Information and Display Materials, and Center for Plastic Information System, Pusan National University, San 30, Jangjeon-dong, Geumjung-gu, Busan 609-735, Republic of Korea b Polymer Chemistry Lab., Kyungil University, Hayang 712-701, Republic of Korea c Department of Chemistry, Dong-A University, Busan 604-714, Republic of Korea article info Article history: Received 13 September 2010 Received in revised form 10 November 2010 Accepted 15 November 2010 Available online 17 December 2010 Keywords: Solution-processed PhOLEDs Iridium(III) complex Deep-red abstract A new series of red emitting phosphorescent Ir(III) complexes, [10-hexyl-2-(4-phenylquinolin-2- yl)-10H-phenothiazine]Iridium acetylacetonate [(PQHPT) 2 Ir(acac)], [10-hexyl-2-(4-phenylquinolin-2- yl)-10H-phenothiazine]Iridium picolinic acid [(PQHPT) 2 Ir(pic)] and [10-hexyl-2-(4-phenylquinolin-2- yl)-10H-phenothiazine]Iridium picolinic acid N-oxide [(PQHPT) 2 Ir(pic-N-O)] based on 10-hexyl-2-(4- phenylquinolin-2-yl)-10H-phenothiazine (PQHPT) main ligand and acetylacetonate (acac), picolinic acid (pic) and picolinic acid N-oxide (pic-N-O) ancillary ligands were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs). The photophysical, electrochemical and electroluminescent (EL) prop- erties of Ir(III) complexes were investigated. All of the Ir(III) complexes had high thermal stability and emitted deep-red light with an excellent color purity at CIE (Commission International de l’Eclairage) coordinates of (0.67, 0.30). The red emitting PhOLEDs based on ITO/PEDOT:PSS/TCTA:TPBI:TPD:Ir com- plex/cathode exhibit a maximum external quantum efficiency of 0.51% and luminance of 180 cd/m 2 , respectively. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Organic light-emitting diodes (OLEDs) are currently attracting a lot of attention owing to their potential application in the field of full-color flat panel displays as an efficient and low cost alternative to the widely used liquid crystal displays [1]. In particular, due to the realization of 100% internal quantum efficiency, phosphorescent organic light-emitting diodes (PhOLEDs) materials have big possi- bility to develop highly efficient than fluorescent emitting materials [2,3]. Because the vacuum deposited PhOLEDs show good device performances than that of solution processed PhOLEDs, a lot of PhOLEDs have been fabricated by vacuum deposition process [4–7]. However, the utilization of multiple layers in vacuum deposited PhOLEDs implies complex in device fabrication, leading to higher fabrication costs and difficulty in large area substrates. To overcome these problems, the solution processed PhOLEDs is being devel- oped due to the merits of simple manufacturing process and large area substrates. There have been many studies about the solution processed PhOLEDs using small molecule or polymeric phospho- ∗ Corresponding authors. Tel.: +82 51 510 2727; fax: +82 51 581 2348. E-mail addresses: jlee@donga.ac.kr (J.W. Lee), shjin@pusan.ac.kr (S.-H. Jin). rescent emitting materials [8–10]. A large number of researchers focus on deep-red phosphorescent materials because general red fluorescent emitters are not as efficient as green and blue emitters in its OLED performance. In our previous report, we reported the synthesis and charac- terization of red-emitting Ir(III) complexes for solution-processed PhOLEDs with high efficiency, good device performance and an excellent color purity at CIE coordinates of (0.65,0.34) [11]. Phenothiazine (PT) is a well known heterocyclic compounds with electron rich sulfur and nitrogen heteroatoms. The PTs group showed strong luminescence, high photoconductivity and reversible oxidation processes [12]. Moreover, the nonplanar PT ring structure can restrict -stacking aggregation, which prevents the detrimental pure singlet excitation recombination process [13]. The phenylquinoline (PQ) derivatives exhibited excellent electron acceptors and electron transport properties [14,15]. Therefore, in this paper, we report the synthesis, redox, photo- physical, and electroluminescent (EL) properties of new deep-red emitting heteroleptic Ir(III) complexes by making use of 10-hexyl- 2(4-phenylquinolin-2-yl)-10H-phenothiazine (PQHPT) as a main ligand from synergistic effects between PQ and PT derivatives and acetylacetonate (acac), picolinic acid (pic) and picolinic acid N- oxide (picN-O) as an ancilary ligand for solution processing of the 0379-6779/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2010.11.019