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The Role of Ruthenium and Rhenium Diimine Complexes in Conjugated Polymers That Exhibit Interesting Opto‐Electronic Properties
Author(s) -
Ng Po King,
Gong Xiong,
Chan Suk Hang,
Lam Lillian Sze Man,
Chan Wai Kin
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011015)7:20<4358::aid-chem4358>3.0.co;2-m
Subject(s) - ruthenium , diimine , materials science , photochemistry , rhenium , conjugated system , polymer , transition metal , bipyridine , polymer chemistry , chemistry , organic chemistry , catalysis , crystal structure , metallurgy , composite material
This paper reports the synthesis and opto‐electronic properties of different conjugated polymers that contain the diimine complexes of ruthenium or rhenium. Conjugated poly(phenylene vinylene)s that contain aromatic 1,3,4‐oxadiazole and 2,2′‐bipyridine units on the main chain were synthesized by the palladium catalyzed olefinic coupling reaction. Other types of polymers based on 1,10‐phenanthroline bis(2,2‐bipyridyl) ruthenium( II ) or chlorotricarbonyl rhenium( I ) complexes were also synthesized by the same reaction. In general, these polymers exhibit two absorption bands due to the π–π* transition of the conjugated main chain and the d–π* metal‐to‐ligand charge‐transfer transition of the metal complex. As a result, the photosensitivity of the polymers beyond 500 nm was enhanced. Charge‐carrier mobility measurements showed that the presence of metal complexes could facilitate the charge‐transport process, and the enhancement in carrier mobility was dependent on the metal content in the polymer. In addition, we have also demonstrated that the ruthenium complex could act as both photosensitizer and light emitter. Photovoltaic cells were constructed, and they were subjected to irradiation with a xenon arc lamp. Under illumination, the short circuit current and the open circuit voltage were measured to be 0.05 mA cm −2 and 0.35 V, respectively. The polymers were fabricated into single‐layer emitting devices, and light emission was observed when the device was subjected to forward bias. The maximum luminance was determined to be 300 cd m −2 , and the external quantum efficiency was approximately 0.05 to 0.2 %. Although the efficiency was relatively low when compared with other devices based on organic materials, we have demonstrated the first examples of using transition metal complexes for both photovoltaic and light‐emitting applications.