Effects of vertically aligned ZnO nanorods surface morphology on the ambient-atmosphere fabricated organic solar cells

Abstract

The present study evaluates the effects of ZnO nanorods electron transport layer morphology synthesized using the low temperature chemical bath method on the performance of organic solar cells. The photoactive layers consisted of P3HT as electron donor and PCBM as electron acceptor. Two ZnO nanorods electron transport layers were studied, one with a smooth surface and a decorated surface. Well-defined ZnO nanorods with perfect hexagonal shapes could be synthesized by chemical bath deposition. Structural characterization confirmed that the vertically aligned ZnO nanorods were successfully obtained in pure form. Performance analysis revealed that the use of decorated ZnO nanorods increased the overall performance relative to the uncoated ZnO nanorods, attributed to the possible increase of light paths on the ZnO nanorods. The best device was obtained from annealed decorated ZnO nanorods ETL having PCE of 7.38%, Voc of 0.63 V, Jsc 18.44 mAcm−2 and FF of 0.60. Solar cells made from decorated ZnO nanorods ETL presented high Rsh of 1311.67 Ω.cm2 and 1497.23 Ωcm2 for as-synthesized and annealed ZnO ETL, respectively. In general, the strategy of decorating ZnO nanorods ETL is an important strategy to fabricate highly efficient organic solar cells and thus may have good potential for many other organic solar cells comprising other polymers apart from P3HT. Even though the efficiency obtained is low compared to the PCE achieved so far, this study gives the observation that may be possibly useful in the further improving PCE of already achieved high efficiencies.