The escaped and trapped emission in organic light-emitting devices

The escaped and trapped emission of organic light-emitting diodes was investigated by an integrating sphere and a fiber spectrometer. It was found that the ratio of escaped emission to the escaped and trapped in the substrate emission is 71%. In order to explain our experimental results, we extended the half-space dipole model, in which the dipole radiation pattern is taken into account. The calculated escaped and trapped emission of devices agreed well with our experiments. Our experimental and theoretical results is expected to be an instruction to the optimization of device structures for improving the out-coupling efficiency.