| As the global energy demand continues to increase year by year, the limiting supply of main energy sources (i.e. oil, coal, natural gas) and their detrimental long-term effects on the natural balance on our planet, force people to search for renewable clean energy. Solar cell is one of major energy in the future, which is the foundation of the Photovoltaic technology. The power conversion efficiency of photovoltaic cells based on inorganic materials increase to about 20%.However, the high cost and complicated processing limited their widely use. But the high cost for manufacture limits them to be widely used. Organic and polymer solar cells, based on organic and polymer materials as active layer, has the advantage of light weight, plenty of choices for active layer, low cost and easily being large-scale etc.Organic and polymer heterojunction solar cells compose of cathode, anode and active layer (donor and acceptor).The process of power conversion contains six steps:(1) absorbs of sunlight. (2) engender of excitons. (3)diffuseness of excitons. (4) excitons be transformed into electron-hole pairs. (5) charge transfer. (6) charge collection.The derivatives of polythiophene are a kind of important and significant conjugated polymer. And it is proved that C60- derivatives are the most efficient electron acceptor for organic solar cells. The application of these materials is very wide.This thesis mainly discussed on polymer heterojunction solar cells, and did research on the influence of film thickness to the solar cells performance. The structure of polymer heterojunction solar cell was ItO/nc-TiO2/P3HT:PCBM/CuPc /Au, P3HT:PCBM blend was the active layer, CuPc was hole transport layer, and TiO2 was electron transport layer.More details are listed below:1. In the Introduction part, the basic concepts of solar power and solar cells were described. And reviewed the recent works focusing on materials of active layers, device physics and processing, novel device structure, and so on.2. In the second part, the work principle of solar cells was introduced and detailed discussion was made about the work principle of polymer solar cells. In addition, electric property of polymer was introduced taking polythiophene and C60- derivatives for example.3. In the third part, the preparation and characterization of nc-TiO2 was introduced. A kind of structure was designed: ITO/ nc-TiO2/P3HT:PCBM /Au. Under the simulated sunlight which power is 100mW/cm2, the short-circuit current achieved 4.32mA , open circuit voltage achieved 0.44V and EQE achieved 0.82%.We synthesized P3HT:PCBM blend, the absorption spectrum of which had a strong absorption peak in 450nm-650nm.4. In the forth part, it discussed about the influence of variable thickness of active layer on the performance of device. The short-circuit current achieved 6.08mA , open circuit voltage achieved 0.54V and EQE achieved 0.99%, when the rotate speed was 500r/min.5. In the last part, firstly, CuPc (10nm) was inserted between the active layer and Au electrode as hole transport layer by thermal deposition. The short-circuit current achieved 5.53mA , open circuit voltage achieved 0.54V and EQE achieved 1.52% . The absorption spectra of CuPc have two peaks in 400nm-500nm and 600nm-700nm.. The composite absorption spectra have been expansion markedly and have a strong absorption in 450nm-650nm and. 675nm-750nm. The influence of variable thickness of CuPc on the performance of device was researched. It was found out that performance of device achieved best, when thickness of CuPc was 10nm.
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