Spin-dependent delayed luminescence from nongeminate pairs of polarons inπ-conjugated polymers

Abstract
We measured cw photoinduced absorption (PA) and spin-12 PA- and photoluminescence detected magnetic resonance (PADMR and PLDMR, respectively) in films of two representative π-conjugated polymers; poly(phenylene-vinylene) and polythiophene. From the dependences of the polaron PA and PLDMR on the laser excitation intensity we conclude that the PLDMR is due to spin-dependent delayed luminescence from nongeminate pairs of polarons. Our findings imply that spin-dependent exciton formation in polymer light-emitting diodes leads to enhanced emission efficiency.