Performances correlated with the device layout (sizes of ITO electrode and photoactive layer) and the illuminated photoactive area (ILA) in polymer-based solar cells (PSCs) consisting of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and vertically aligned ZnO nanorod array (ZnO-NA) are systematically investigated. MEH-PPV/ZnO-NA solar cells with the same architecture are prepared with three kinds of layouts. It is found that the device layout and ILA size impose significant effects on the steady-state and dynamic performances of the devices even though the device architecture, the materials property and the Au electrode in the devices are not changed, and the manners in which the device characteristics correlate to the device layout and ILA size are revealed, providing the optimized layout for efficient MEH-PPV/ZnO-NA device and the appropriate layout for accurate performance characterization. The present study reports the significant advances in understanding the ILA- and layout-correlated device performances, which will help to guide the design and characterization of PSCs. (C) 2012 Elsevier Ltd. All rights reserved.