We investigate the open circuit voltage (VOC) of stacked bulk heterojunction (BHJ) organic solar cells based on conjugated polymer and fullerene derivative by spin-coating method. Poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) blended with [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) is used as a photoactive layer. The structure is ITO(lower BHJ cell)PEDOT:PSS/MDMO-PPV:PCBM/ITO/(upper BHJ cell)PEDOT:PSS/MDMO-PPV:PCBM/Al. VOC of the stacked cell is 1.34V and is about 1.6 times as large as that of single BHJ organic solar cell. VOC of the stacked cell is not proportional to the number of photoactive layers, but is the sum of the VOC values of the upper and the lower BHJ cells.
The bombardment of various types of energetic ions during rf-superimposed dc magnetron sputter deposition was investigated in detail and their effects on the structural and electrical properties of Al-doped ZnO (AZO) films were analyzed. Aside from the expected energetic negative oxygen ions (i.e., O- and O2
-), various other negative ions (i.e., AlO-, AlO2
-, AlO3
-, ZnO-, and ZnO2
-) with a high energy were clearly observed. Such negative ions were found to be generated on the target surface and accelerated towards the substrate by the full cathode voltage. Furthermore, we found that the energy of these negative ions decreased with decreasing plasma impedance by superimposing rf power on dc sputtering. The resistivity of the AZO films deposited using the rf-superimposed dc sputtering was much lower than that of the films deposited using conventional dc sputtering. Such a decrease in resistivity should be attributed to reducing the damage of AZO films by suppressing the bombardment energies of various types of energetic negative ions impinging on a growing film surface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.