Inverted Organic Photovoltaic Cell with ZnO Nanorod Structure

抄録

The electrical and physical properties at the interface between the ZnO electron transport/collection layer and an organic photoactive layer play important roles in determining photovoltaic performance. Therefore, we have fabricated ZnO nanorods and optimized the coating conditions used for deposition of the ZnO seed layer, which serves as a nucleation site for crystal growth. First, the relationship between the concentration of the ZnO precursor solution (zinc acetate dihydrate and hexamethylenetetramine in methanol) and diameter of the ZnO nanorods was examined, and we showed that the diameter continuously decreased with increasing concentration, reaching a minimum of 23 nm. Further, we investigated density of ZnO nanorods and photovoltaic performance of the inverted cell as a function of the rotation speed used during the spin coating process to deposit the ZnO seed layer. A low density of ZnO nanorods was obtained when the rotation speed was low, and this caused the short circuit current density, open circuit voltage, and fill factor of the organic photovoltaics to decrease. As a result, a maximum photoconversion efficiency of 3.0% was achieved, and this value was 1.6-fold greater than that measured using a reference device containing no ZnO nanorods (photoconversion efficiency: 1.9%).