Bulk heterojunction photovoltaic cells based on vacuum evaporated cadmium sulfide–phthalocyanine hybrid structures

Bulk heterojunction (BHJ) photovoltaic (PV) cells have been prepared by vacuum co-deposition of inorganic cadmium sulfide (CdS) and organic zinc phthalocyanine (PcZn) materials. Characteristics of the BHJ cells were compared with the cells based on vacuum evaporated bilayer CdS/PcZn heterojunctions, and it was found that the BHJ structure possesses higher PV performance due to higher interface area at which excitons can dissociate. Variation of the component ratio in the BHJ devices and comparison of their photocurrent spectra allowed us to distinguish the contribution of CdS, CdS/PcZn interface and PcZn to the PV response. The mechanism of charge transport was attributed to the model of space-charge-limited current with traps; however, the concentration of traps was different in the bilayer and BHJ structures.