The experimenters have measured the I-V characteristics of the tandem device, and also of each of the separate types of junctions, and find that the open-circuit voltage of the tandem device is close to the sum of the open-circuit voltages of the separate cells. Tandem cell operating properties are clearly shown in Figure 7.11.
It appears that these efficiency values are the best ever obtained for polymeric organic cells of any type. The authors [92] discuss briefly that the tandem cell properties are reasonably stable over storage and running times, but note that any major application would require close attention to mechanisms of degradation.
7.1.4
