The Study Of Influential Factors Of The Performance Of Polymer Solar Cells Based On MEH-PPV:PCBM

Solar cells are devices transferring the sun-light to electrical energy. In this paper, the factors that influence the performance of organic solar cells based on polymer were studied in order to improve performance of devices. The main works are as follows:1. Study the influence of different weight ratio and annealing treatment on bulkheterojunction organic solar cellsBased on the bulk heterojunction (BHJ) organic solar cell (OSC) with the device structure of ITO/PEDOT:PSS/MEH-PPV:PCBM/Al, we firstly studied the influence of different weight ratio treatment to MEH-PPV:PCBM BHJ solar cells. It turned out that the best weight raito should be 1:4 for MEH-PPV:PCBM BHJ solar cells.Then we do annealing treatment at 150℃for 8 mins, which improved the phase separation of tfie organic materials, and balance the carrier mobility. This treatment enhanced the performance of the devices. Therefore, we studied the different annealing temperature (80℃for 8 mins,220℃for 8 mins) and gradient annealing temperature treatment(80℃for 4 mins and then 150℃for 4 mins). The results proved that annealing treatment with gradient temperature could further enhance the phase separation and form a better interpenetrating network structure; and annealing at 150℃will be better able to lower the series resistance, improve and balance the carrier mobility, which will increase the fill factor of the devices.2. We introduced anode modification layer of MoO3 (15nm), which could let interface dipole layer formed in between the ITO/Oxide interface. This interface dipole layer could shift the vacuum energy level of the organic materials, and enhance the build-in potential, and improve hole extraction at the anode/organic interface. The result turned out that the Voc of the devices increases because of enhancement of the built-in potential. This improvement will due to the thickness of the modification layer. Additionally, we find the oxide layer could cause interference of the incident light and match that with the absorption spectrum of the active layer, which could improve the performance of the devices.3. Based on the BHJ of MEH-PPV:PCBM, we introduced PVK with different weight ratios. For the hole mobility in MEH-PPV is much lower than the electron mobility in PCBM, we introduced PVK in order to balance the carrier mobility of the devices. Meanwhile, the photoluminscence of PVK overlaps with the absorption spectrum of MEH-PPV:PCBM materials. Thus, the energy conversion efficiency could be further enhanced by self-absorption. The experiment turned out that the introduction of PVK may harm the D/A interface. But further introduction of more PCBM will recover the D/A interpenatrating network. And because of the improved hole mobility by PVK, the improvement of devices became achievable. However, it should be noted that a trade-off between the higher hole mobility and lower absorption efficiency both by introducing PVK must be found.