Photocurrent enhancement and photoresponse properties of organic photodetectors with iridium complexes doped in conjugated polymers

Abstract Properties of solution-processed organic photodetectors with iridium (Ir) complexes doped in fluorene-type conjugated polymer, poly(dioctylfluorene-co-benzothiadiazole) [F8BT] as a host were investigated. F8BT devices had blue sensitivity. Ir complexes as triplet materials can enhance the incident-photon-to-current conversion efficiency (IPCE) of the devices when their triplet levels are lower than the lowest excited singlet states (S 1 ) of the host and higher than the lowest excited triplet states (T 1 ) of the host. A bilayer F8BT device utilizing solution-processable starburst molecular and tris(2-phenylpyridine)iridium(III) [Ir(ppy) 3 ] as a hole transporting layer and a dopant, respectively, showed larger photocurrent than an non-doped bilayer device under high applied voltage. For the bilayer device with Ir(ppy) 3, a cut-off frequency of more than 10 MHz was observed under forward bias of 5 V and clear response pulses at 10 MHz were received using a sinusoidal modulated laser light illumination.