Principal processes of organic–inorganic hybrid solar cells using the example of ZnPc with ZnO

Hybrid solar cells make use of the high absorption coefficient of the organic material and good transport properties of the inorganic counterpart. Little experience exists in the combination of inorganic semiconductors and small aromatic molecules. Here, an organic–inorganic interface within a hybrid solar cell is fabricated and characterized using zinc(II)-phthalocyanine (ZnPc) and zinc oxide (ZnO). The band structure within the device is derived from photoelectron spectroscopy (PES). Hereby, the open circuit voltage is estimated and compared to current–voltage characteristics. The exciton diffusion length is determined to be 16 nm by using spectrally resolved photocurrent measurements. The ZnPc/ZnO interface is shown to be the place for the exciton dissociation, i.e., to be the active interface. Nanostructures were used to shorten the distance between the place of exciton generation and exciton dissociation. Electronic structure of the hybrid solar cells with indication of the main processes, i.e., exciton diffusion, exciton dissociation, and charge extraction.