5. Electrodes and interface layers

To begin on this point, we can take up the general schematic of a volume heterojunction cell whose active layer consists of P3HT and PC ₆₁ BM (Figure 13 a) and the corresponding energy levels (Figure 13 b). It should be noted that these energy levels are sometimes extracted using different techniques and they are given for information only.

The structure shown in figure 13 is called a direct structure because light enters the active...