Abstract
Polymer solar cells exhibit many advantages such as the lightweight、processing feasibility and the potential to scale up to large area. Therefore polymer solar cells have been under intensive research. It usually contains single layer bulk heterojunction structure in the device. With large area for exciton separating, the efficiency of the device can be greatly improved. Recently, a better structure called ordered bulk heterojunction has been developed in dye-sensitized solar cells and molecular solar cells. It helps carriers transport and increases the efficiency of the device dramatically. In our study, we use P3HT conjugated polymer as hole transport material and 5nm×10nm CdSe inorganic colloidal nanorods as electron transport material. Blending two of them as the active layer, we form a bulk heterojunction film on the device with spin-coating. Under the illumination of monochromatic light with 532nm wavelength, the power conversion efficiency reaches 1%. In order to increase the carrier transport efficiency, we use single layer bulk heterojunction as basic structure and develop multilayer structure with spin-coating to achieve the similar effect of ordered bulk heterojunction. Using the sintering property of nanocrystals when annealed, we can create multilayer bulk heterojunction structure by slightly mixing the layers at the interface. In this study, we successfully developed blend/CdSe and blend(P3HT-rich)/blend ordered bulk heterojunction structures. Comparing to single layer bulk heterojunction, the series resistance decreases several times in ordered bulk heterojunction structure. It makes short circuit current and fill factor increase largely. The power conversion efficiency in blend/CdSe structure is 2.4% under the illumination of monochromatic light with 532nm wavelength. In blend(P3HT-rich)/blend structure, the efficiency even reaches 3.1%！