Bathocuproine/Ag复合电极对于聚合物光伏器件效率和稳定性的影响

Effects of bathocuproine/Ag composite anode on the performances of stability polymer photovoltaic devices

采用Bathocuproine/Ag(BCP/Ag)复合电极代替Ca/Al复合电极,制备PTB7:PC71BM作为光敏层的聚合物光伏器件,并通过改变BCP薄膜厚度来研究BCP/Ag复合电极对于器件光电转换器和稳定性的影响.研究发现:在光敏层和金属电极之间插入BCP修饰层后,器件性能得到了显著的改善,在BCP厚度为5 nm时,器件的效率达到了6.82%,且略高于Ca/Al复合电极的器件效率;相比于采用Ca/Al复合电极的器件,BCP/Ag复合电极增大了器件的短路电流和外量子效率,使器件效率得到提高;同时器件的稳定性得到了显著的改善,BCP/Ag复合电极器件的衰减速率几乎和未插入BCP的器件衰减速率相同,相对于Ca/Al复合电极器件大幅提高.

In this work, the composite anode of BCP/Ag replaces the ／ acts an as active layer for polymer solar cells. Calcium （Ca） is composite anode of Ca/A1, and the PTB7 ： PC71BM not a desirable candidate as electron extraction layer （EEL） for long-term stability polymer solar cells （PSCs） on account of its nature of active metal. And then, due to the poor stability of A1, which is not a desirable candidate as electrode, the bathocuproine （BCP） layer acts as an exciton blocking layer in organic device such OLEDs and small molecule solar cells, which has a k value that is close to zero for a broad range of wavelengths. The Ag has the nature of better chemical stability and conductivity than A1. In the device architecture described bel.ow, we replace the typical back metal electrode composed of a thin Ca layer and a thicker A1 electrode by a few nanometer thick bathocuproine （BCP） layer and a thick 150 nm Ag layer. We investigate the effects of BCP thickness on the power conversion efficiency （PCE） and stability. The results reveal that the photovoltaic performances are improved, and a PCE of 6.82% at the 5 nm of BCP thickness, higher than the PCE of Ca/A1 acted composite anode, is achieved. The substitution of BCP for Ca, can largely enhance light harvesting and exhibits an optimal light absorption by the active layer. This enhanced reflectivity of the buffer layer/electrode back contact results in an increase of the short circuit current. Compared with the devices of Ca/A1 composite anode, it increases Jsc and external quantum efficiency with BCP/Ag composite anode. At the same time, it has the better stability of BCP/Ag composite anode of device, and almost the same PCE decrease ratio as free BCP devices and significantly improves the stability compared with Ca/A1 composite anode. The stability test shows the better stability of BCP/Ag as composite anode than that of Ca/A1 composite anode. The PCE of the device with Ca/A1 as composite anode rapidly decreases by about 70% after 50 hour servicing due to the poor stabilities of Ca and A1. The device with BCP/Ag as composite anode shows favorable stability, owing to the PCE moderate decrease by less than 30~ after the same story time. Our results indicate that substitution of BCP/Ag for Ca/A1 composite anode is an alternative candidate for high performance and longterm photo stability PSCs.