Research On The Performance Optimization Of Organic Solar Cells

Solar energy is regarded as the best alternative energy because of inexhaustible, clean and non-polluting. Compared with the conventional inorganic silicon cells, the organic photovoltaic with low-cost, large area and flexibility has the widespread concern.The concept of BHJ provides the most straightforward solution to maximize internal D-A interfacial area for efficient charge separation. The interpenetrating network structure will provide a larger area for exciton diffusion. Therefore, how to effectively control the morphology of the active layer is particularly important for optimizing device performance. In addition, select a proper buffer layer through the design of the device structure to reduce the interfacial barrier between the electrode and the active layer, which will help to improve the mobility and collection of carriers. With the purpose of improving the efficiency and stability of organic solar cells, we focus the research on the optimization of the performance from the three aspects as follows:Improved power conversion efficiency (PCE) and stability of organic bulk heterojunction (BHJ) solar cells based on poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene)(MEH-PPV) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends have been obtained by using ditert butyl peroxide (DTBP) as an additive.The effect of the DTBP contents on the performance of photovoltaic cells was investigated. The results revealed that efficiency enhancement of MEH-PPV:PCBM solar cells can be realized by carefully tuning the contents of DTBP. Compared to the control device, the optimized device with0.5wt%DTBP additive exhibits enhanced performance with Jsc of (3.51±0.21) mA/cm2, FF of (44.45±0.71)%, and PCE of (1.31±0.08)%, increased by9.3%,8.0%and22.4%, respectively. The stability of the device was found to be improved by adding0.5wt%ratio of DTBP.Comparative study on the performances of organic bulk heterojunction (BHJ) solar cells based on regioregular poly (3-hexylthiophene)(P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends was investigated by using ReO3and Re2O7as anode buffer layer, respectively. Compared with the traditional V2O5or MoO3anode buffer layer, ReO3and Re2O7show a lower thermal evaporation temperature (about340℃). Mixed anode buffer layer of PEDOT:PSS/ReO3with different thickness was investigated. However, the results showed that ReO3and Re2O7reduced the performance of the device.Organic bulk heterojunction (BHJ) solar cells based on PCDTBT as the donor and PC71BM as the acceptor materials were fabricated with the structure of ITO/PEDOT:PSS/PCDTBT:PC71BM/LiF/Al. The performance of the device with different solvents and different concentration ratio of donor and acceptor was studied. The results showed that the optimum concentration is1:2and the optimum solvent is o-dichlorobenzene (ODCB). Meanwhile, device performance based on CF3COOHCs as cathode buffer layer was explored. However, negative effects were founded for the CF3COOHCs cathode buffer layer.