Preparation And Performances Of Inverted P3HT:PC₆₁BM Polymer Photovoltaic Devices

The universal materials, device architecture, working principle and recentprogresses of polymer solar cells （PSCs） are briefly introduced in the dissertation. Inthe bulk heterojunction （BHJ） PSCs, appropriate interface materials and enhancedmobility of charge carriers are essential for improving the power conversionefficiency （PCE）. So the effects of the properties of interface material and smallmolecule additive on the performance of inverted P3HT: PC₆₁BM PSCs are studied inthis thesis. Main researchers are as follows:1. TiO₂films have been prepared by magnetron sputtering method, and effects ofthe crystallity and thickness of the TiO₂films on the performance of inverted P3HT:PC₆₁BM PSCs have been studied. With a thickness of42nm, the unannealed TiO₂film is used as the electron transport layer, and the device assembled has thephotovoltaic parameters: Jsc=9.11mA.cm-2; Voc=0.63V; FF=0.50; PCE=2.85%.When further annealed at450℃for30min, the device parameters are: Jsc=10.02mA.cm-2; Voc=0.66V; FF=0.57; PCE=3.75%. It is proved that increase of thecrystallinity of the TiO₂films can affect the photovoltaic performance of the device.Meanwhile, we investigated the effect of the TiO₂thickness on the deviceperformance. It is indicated that the TiO₂thickness does not affect the transmittanceof the visible light, and the TiO₂can absorb more ultraviolet light with the increasedthickness, which may protect the photoactive layer.2. DH4T was added into the photoactive layer of P3HT: PC₆₁BM as an additivein inverted PSCs, and the effect of the concentration of DH4T on the photo toelectricity efficiency of the inverted PSCs was investigated. The study result indicatedthat the introduction of the DH4T could help to improve the device performance.With photoactive layer of P3HT: PC₆₁BM, performance parameters of the generaldevice are: Jsc=10.00mA.cm-2; Voc=0.66V; FF=0.56; PCE=3.68%. When DH4Twas added with the concentration of10%, the device parameters are: Jsc=10.30mA.cm-2; Voc=0.67V; FF=0.₆₁; PCE=4.22%. It is demonstrated that theintroduction of DH4T mainly increase the fill factor for the device, while short circuitcurrent has a little increase and the open circuit voltage almost has no change. Theaddition of the small molecule could increase hole mobility, which improves the fill factor and short circuit current. The open circuit voltage is mainly attributed to theHOMO level of donor and LUMO level of acceptor, thus which almost preserves.