Amplified Spontaneous Emission And Electroluminescence From F8BT:P3HT

Conjugated polymers are promising materials in solid-state lasers on account of their high photoluminescence quantum efficiency (PLQE), simple fabrication and broad spectra. Optically pumped lasers based on conjugated polymer have got huge progress in recent years and people hope to explore the possibility of electrically pumped polymer lasers. Because of the problems such as high threshold and low charge mobility of polymers, it is difficult to achieve this goal. More and more efforts have been made to demonstrate electrically pumped lasers by improving the current injection and lowering their lasing threshold. In this thesis, our work is focused on lowering the threshold of amplified spontaneous emission (ASE) and improving the charge injection and mobility by blending poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) with poly(3-hexylthiophene) (P3HT).1. The temperature dependence of ASE from blend film of F8BT and P3HT has been investigated. We measured ASE from blend film with various F8BT:P3HT mass ratio and F8BT film at room temperature and studied the temperature dependence of F8BT film and blend film with 20% P3HT in the temperature range of 80-320 K. The results show that with an increasing ratio of P3HT, the threshold of blend film first decreases and then increases at room temperature. Lowest ASE threshold was achieved for the blend with 20% P3HT ratio. When the temperature dropped from 320 K to 80 K, ASE threshold of blend (20% P3HT) decreased and ASE output intensity increased. In addition, the exciton binding energy of F8BT and blend (20% P3HT) film was calculated by nonlinear fitting of the dependence of photoluminescence intensity on temperature.2. The carrier mobility of the blends with different P3HT mass ratio had been measured by time-of-flight. With the increase of P3HT, the mobility of electron and hole both increased. The polymer light-emitting devices were fabricated with blends of F8BT and P3HT as the emission layer. The J-V-L curves of the devices had been measured. The charge injection voltage decreases with the increase of P3HT. We also measured the transient electroluminescence of F8BT:P3HT blend films under the pulsed electric excitation. The EL devices with blend active layer show shorter rising time and the falling with the increase of P3HT.