Inverted hybrid photovoltaic devices on nonplanar surface for efficient charge carrier separation

Abstract

In this paper, we present an inverted organic solar cell fabricated on a cylindrical glass rod. Because of the nonconventional geometry of the substrate, a variety of deposition processes were employed, including atomic layer deposition, hydrothermal growth, dip coating, and thermal evaporation. ZnO nanorod array used as an electron-selective layer improved the device performance compared with devices without ZnO nanorods owing to its role as a vertically guided electron pathway. The thickness and morphology of the active layer [poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM)] created by the dip coating process were optimized by varying the substrate lifting speed. In addition, thermal annealing of the active layer induced an appropriate level of microphase separation of donors and acceptors, improving the charge separation and resulting in a maximum power conversion efficiency (PCE) of 1.38%. Finally, we conclude that solar cells on a curved surface improve the normalized PCE dependence on the incident angle of sunlight compared with planar solar cells. (C) 2014 The Japan Society of Applied Physics