| A systematic study on the performance of phosphorescent polymer light-emitting diodes (PLEDs) has been carried out. The performance of these phosphorescent PLEDs is affected by several physical properties of the materials employed, including the exciton lifetime of hosts and dopants, the energy levels, and the compatibility of hosts and dopants. The dopant lifetime should be short in order to prevent the self-quenching processes, such as triplet-triplet annihilation and polaron-triplet annihilation. On the other hand, the lifetime of the host material should be long enough to efficiently transfer the energy to the dopants. Additionally, the triplet energy of the host material should be higher than those of dopants in order to confine the excitons on dopants and subsequently lead to the higher device performance. Furthermore, a novel phosphorescent polymer light-emitting electrochemical cell (LEC) is reported which overcomes the problem of high operation voltage of phosphorescent PLEDs. This LEC has low light turn-on voltage (related to the low energy band gap of the host polymer), driving voltage, and, hence, higher power efficiency.;Finally, high performance heterojunction polymer photovoltaic devices are fabricated. The power efficiency of the organic solar cells was enhanced by blending an ionic solid electrolyte, such as polyethylene oxide (PEO) into the active layer. It is believed that the "in-situ photodoping" of the polymer contributes to this enhancement. |
