Studies On Annealing Technology Of P3HT:PCBM Bulk Heterojunction Organic Solar Cells

The solar energy has been used widely all over the world,because the energy crisis and climate issues.The solar cells are emerging as continuous innovation of new materials.Organic material has promoted the research of organic solar cells in the world because of its good flexibility, easy making, extensive source material and low cost. Currently, organic solar cells are gradually improving its energy conversion efficiency, and steadily going forward in the moving towards the road of commercialization and industrial production.As a common method to improve the performance of organic solar cells, the mechanism of annealing has been explored and verified in practice constantly. However, there are still many detailed process of the annealing to study in order to achieve higher energy conversion efficiency and the availability of large-scale industrial production. In this paper, according to the method of controlling variables, make annealing comparison tests on P3HT:PCBM bulk heterojunction organic solar cell.The bulk heterojunction organic photovoltaic devices are made,and the structure of the organic solar cell device is ITO/PEDOT:PSS/P3HT:PCBM/Al. The annealing in all experiments is post-annealing.When the time is 20 min,the performance of the devices in140℃to160℃is better than others.The short-circuit current density is higher than 9.5 mA/cm2, the photovoltaic energy conversion efficiency (PCE) is higher than2.5 %. When the temperature is 150℃, the performance of the devices inl5min-30min is better than others,too. The short-circuit current density is higher than 9 mA/cm, the photovoltaic energy conversion efficiency (PCE) is higher than2.5 %.Integrating the research of annealing temperature and time, make experiment al comparison of the progressive annealing result. Set the initial temperature 140℃, heat for 5min, then transfer to 150℃for 10min, finally 160℃for 5 min.Through this way we can get significantly better device performance parameters compared to other devices.The main performance of this method is the increase in the short-circuit current density,up to 10.34 mA/cm2.The photovoltaic energy conversion efficiency is 3.31 %, fill factor is more than 50 %.The decrease of Rs,increase of EQE can explain this experiment. Microwave heating is a method of lower energy consumption and concentrated heating. It is completely different from other conventional methods of thermal conduction heating, employing microwave oscillations to anneal the active layer.This none-contact and rapid annealing method can made selective effects on active layers and electrode. For the same kinds of devices, under the premise of the low power consumption, adopting microwave annealing method can get performance parameters met or exceed the normal heat conduction annealing mode.We use U-V absorption spectrum and SEM test to explain the above phenomenon.With the consideration of UV absorption spectra and surface morphology of SEM,microwave annealing optimize the network and improve the crystallization of polymer, the higher surface roughness also acceleratecharge transmission.The researchs of these annealing were so little, the related experiments have done in this paper.It can be a good reference for the future research.