A comprehensive photoluminescence (PL)-detected magnetic resonance (PLDMR) study of various vacuum-sealed rubrene films and powders is described. Three PLDMR features are observed and analyzed: (i) A negative (PL-quenching) triplet exciton (TE) resonance at T > 50K, due to reduced spin-dependent fusion of geminate TE pairs to singlet excitons (SEs). (ii) A positive (PL-enhancing) triplet resonance at T < 50K. This resonance is suspected to result from reduced quenching of SEs by a reduced population of polarons and nongeminate TEs, the latter due to the spin-dependent annihilation of TEs by polarons. (iii) A negative spin 1/2 (polaron) resonance, believed to be due to enhanced formation of trions at oxygen centers. As single crystal thin films of oxygen-doped rubrene exhibit exceptionally high room-temperature carrier mobility, the relation of this positive resonance to these transport properties is also discussed.

Date Published: 27 August 2009
PDF: 10 pages
Proc. SPIE 7415, Organic Light Emitting Materials and Devices XIII, 74151Y (27 August 2009); doi: 10.1117/12.827277

Published in SPIE Proceedings Vol. 7415:
Organic Light Emitting Materials and Devices XIII
Franky So; Chihaya Adachi, Editor(s)