We investigate spontaneous emission from a two-level atom embedded in photonic crystals. Due to the photon localization and the quantum interference between the two dressed states, some changes of the radiation field happen, and the energy is transferred among the excited atom, the localized field, the propagating field and the diffusion field. If there is a localized field, it appears quasi-oscillation behaves of the population evolution in the excited level. If there isn't a localized field, it appears no quasi-oscillation. Moreover, there have some steady-state trapped atom populations in the excited level, and the spontaneous emission spectrum near the forbidden gap edge is different from that in the vacuum. All these characteristics depend not only on the relative position of the excited level from the band-edge but also on the photon density of states (or the band-edge smoothing parameter) near the band edge.
The interface formed between a p-type conducting polyaniline layer and a n-type porous silicon wafer was studied. The
contact has rectifying behavior demonstrated clearly by the IV curves. The series resistance Rs in the p-type conducting
polyaniline/n-porous Si diode is reduced greatly and has a lower onset voltage compared with. ITO/n-porous Si diode.
The porous silicon has an orange photoluminescence band after coating with polyaniline. Visible electroluminescence
has been obtained from this junction when a forward bias is applied. The emission band is very broad extending from
600-803 nm with a peak at 690nm.
We have developed an analytical model to calculate the EL profile at high electric field in single layer structure, taking into account the charge injection process at each electrode, fission and recombination of polaron-excitons. By simulation, the influences of injection barriers on EL efficiency and fission distance on recombination efficiency are thoroughly studied. Using either both ohmic contacts or using an ohmic contact to inject the low mobility carrier and a contact limited contact to inject the high mobility carrier can obtain efficient devices. By comparison of the theoretical results with the experimental data reported in the literature, we found this model can reasonably elucidates the influences of some factors on injection and recombination.