Al-DOPED ZnO NANOSTRUCTURED ELECTRODES FOR SMALL MOLECULE ORGANIC SOLAR CELLS

摘要

The effect of Al incorporation into the ITO/i-ZnO seed layer (i-ZnO-SL)/ZnO-nanorods (ZnO-NRs) stack applied as electrode in organic solar cells is investigated. ZnO-NRs were prepared by electrochemical deposition in the presence of an Al-precursor with varied concentrations onto ITO substrates covered with a sputtered intrinsic ZnO seed layer. In a second step, the i-ZnO-SL was replaced by a sputtered ZnO:Al seed layer (ZnO:Al-SL). The effect of Al incorporation into both ZnO(Al)-NRs and ZnO:Al-SLs is tested on solar cells with a C_(60)/ZnPc:C_(60) active layer stack on top of nanostructures. With increasing the Al-precursor concentration in the electrochemical bath, beside the growth of ZnO-NRs, an additional formation of ZnO(Al)-"nanosheets" is detected. Lower shunt resistances of photovoltaic devices with nanosheets were observed pointing to creation of shunting pathways. Thus, the presence of nanosheets resulted in solar cell devices with reduced PV parameters compared to Al-free prepared ZnO-NRs. In contrast to i-ZnO-SLs, ZnO:Al-SLs clearly improve the device performance demonstrating the potential of the ITO/ZnO:Al-SL/ZnO(Al)-nanostructure stack as highly structured electrode.