| Solar energy is the most potential green energy that can be sustainable used in a variety of application fields, while photovoltaic is one of the most developed technologies in the use of solar energy. At present, the first generation solar cell based on crystalline silicon still holds the most of photovoltaic market, however the cost of cell is too high limiting its widespread use. In order to reduce the cost of photovoltaic cells, two improvements were carried out in this work. First, we studied OPV which has unique advantages of easy processing, low-cost, high-performance and compatibility with flexible substrates. At the second part, Si nanopillars have been fabricated to replace planar silicon in order to improve the optical performance. Moreover, organic polymers have been combined with Si nanopillars to fabricate the hybrid solar cell. The organic solar cell devices were fabricated by means of spin coating and vacuum deposition, while Si nanopillars were fabricated by nanosphere lithography. The main work can be summarized as follows:(1) Small molecule materials zinc phthalocyanine(Zn Pc)/ fullerene(C60) were used as active layer. We improved the performance of organic solar cells(OSC) by inserting a cathode buffer layer(CBL) between the active layer and cathode. In this part, the influence of the film thickness of Bphen layer on the electrical characteristics of the device was systematically studied. The results indicated that at an optimal film thickness of 10 nm CBL is essential to enhance device performance by forming improved interfacial contact without introducing current leakage. On the basis of this optimal thickness, we studied bulk heterojunction structure by varying blend composition of Zn Pc and C60. The optimal performances of the BHJ device were obtained in mixing ratio 2:1(Zn Pc: C60), which is mainly attributed to its good carrier transport originating from phase isolation. Finally, we achieved the optimal performance of BHJ structure with PCE of 0.84%, which is 55% higher than that of PHJ structure.(2) Polymer solar cells based on poly(3-hexylthiophene)(P3HT):[6,6]-phenyl C61-butyric acid methyl ester(PCBM) were fabricated in this part. Different organic and inorganic materials were investigated as CBL and the performances of corresponding devices were compared. A novel CBL by doping the organic and inorganic materials was also introduced to improve the device performance. We found that when metal electrode was deposited, the reactive hot metal atoms can lead to chemical interaction at the interface and diffusion into the organic layer. Inserting a cathode buffer layer(CBL) between the active layer and cathode is well applied to enhance the electron transport, to block excitons and to avoid quenching of the electrons and holes. The PCE of the OPV device was improved to 2.78%, which is 75.9% higher than that of device without CBL.(3) A low-cost and controllable method has been developed to fabricate Si nanopillars by means of nanosphere lithography, while hybrid solar cell based on Si nanopillars has been further studied. First, Langmuir-Blodgett film technology was used to deposit the Si O2 nanoparticles matrix on the n-Si(100) wafer, then Inductively Coupled Plasma(ICP) etching was used to fabricate the Si nanopillar array. The influence of the pillar size on the optical performance of the nanopillar array was then investigated, indicating that a smaller diameter and a higher height can lead to a smaller reflectance of the Si nanopillar array. Finally, we fabricated the hybrid solar cell devices based on Si nanopillars/conjugated polymer(PEDOT:PSS)and studied the photovoltaic properties of the devices by I-V test. |
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