Organic Thin Film Solar Cells Research Of Physical Properties

The energy problem is one of many countries pay much attention to in the21stcentury. Solar energy is unlimited, inexhaustible, non-polluting and low-cost. Sohumanbeings can freely use the energy. Because of many advantages, such as lowproduction cost, simple preparation process, a variety of production materials and thefeasibility of large-area manufacturing, organic thin film solar cells has become a newhot spot for solar cell research. Although rapid progress has arrived to study newmaterials and structures, the photoelectric conversion efficiency has been continuouslyrefreshed, we still have long way to go for large-scale commercial applications.It has been shown that the selection of the best active materials and theoptimization of the device structure are two important means to improve the batteryefficiency of photoelectric conversion. The theoretical analysis may help us to deepenunderstanding of the physical properties of the battery; and would provide some way toincrease efficiency. The theoretical analysis include following aspects: analysis of theorganic layer thickness in the device, the donor-acceptor microscopic structure of thephotocurrent, exciton solution from the impact of efficiency, recombination processes,and open circuit voltage-short circuit current equivalent model.In this paper, two main problems influencing photo-voltage efficiency are analyzed:exciton diffusion and optical absorption, and the relationship between optical absorption,and the power conversion efficiency with the thickness of the film. Considering that theelectric field strength and carrier density dependent mobility formula is popular inliterature, but the corresponding drift and Poisson equations can not be analyticallysolved, we thus derived an analytic approximate current-voltage (J-V) equation. Thecomparison with experimental data shows that the approximate J-V relation issatisfactory. We also modified the equivalent circuit in literature, made somecalculations on current-voltage of organic diodes, and compared the results withexperimental data.