Research Of The Efficiency Of Bulk Heterojunction Organic Devices Improved By The Annealing And Modified Layer

With the increase of the demand for energy, the storage capacity of traditional fossil energy source such as coal、oil in earth is not optimistic. At the same time, the global environmental problems and energy issues results the human survival and development facing serious challenges. Development of environmentally friendly,renewable energy alternative to traditional fossil energy has become the key to solve the global energy and environmental issues. Among, solar energy with its unique advantages such as inexhaustible、abundant and non-pollution has attracted human ’s much attention. In 1954, Pearson et al in USA Baer lab created the first block of p-n crystalline silicon solar cell devices in the world, opening the prelude of solar photo voltaic power generation. However, due to the high cost of preparation, complex production process and long cost recovery cycle, mono crystalline silicon and poly crystalline silicon as the representative of silicon solar cells is difficult to put into practical application in large scale.Due to its advantages such as low cost, flexibility, portability, apt to design and synthesis, organic material is vital to develop novel solar cell with low cost non-pollution and large-scale investment. In 1995, Yu G. et al. from California University of Santa Barbara presented the concept of bulk heterojunction polymer solar cells firstly. Recently, the researches on the bulk heterojunction polymer solar cells are mainly concentrated on improving the energy conversion efficiency. The researchers improved the energy conversion efficiency of bulk heterojunction polymer device mainly through adjusting energy structure of organic materials, enhancing the optical field of active layer, improving modified layer of organic devices, optimizing the structure of bulk heterojunction polymer devices and so on.The processed techniques and tested process of the bulk heterojunction organic solar cells were described in the third chapter of this paper. The effects of thermal annealing on the energy conversion efficiency of P3HT:PCBM devices were investigated. The organic devices whose structure is ITO/PEDOT:PSS/P3HT:PCBM/Al were prepared, and under 150 OC, the devices were annealed. Then the performanceparameters of the devices were tested, Voc=0.5801 V,Jsc=5.775 m A/cm2,FF=0.4603,and the energy conversion efficiency η=1.542%. The improvement of the devices performance parameters is attributed to the appropriate annealing, which not only broadens the spectrum absorption range to bulk materials, but also optimizes the morphology of active layer.The effects of Li F cathode modified layer on the energy conversion efficiency of the P3HT:PCBM device in the fourth chapter of this paper. The P3HT:PCBM devices were modified by Li F insulating layer, the performance parameters Voc=0.6204 V,Jsc=10.85 m A/cm2, FF=0.5247 and energy conversion efficiency η=3.532% 。 The improvement of device performance parameters is attributed to the formation of dipole moment in the Al interface by the appropriate thickness of the Li F modified layer. However, when the ITO/PEDOT:PSS/P3HT:PCBM/Li F/Al were annealed, the energy conversion efficiency decreased to 1.417%, which is attributed to the diffusion of Li F into the active layer due to the annealing, damaging morphology of the active layer.