We propose that treating the surface of the bottom subcell active layer composed of regioregular poly (3-hexylthiophene) (P3HT): indene-C-60-bisadduct (ICBA) with 1-hexanol can improve the wettability of aqueous PEDOT:PSS on its top as a hole transport layer in the inverted tandem polymer solar cell (t-PSC), allowing a fabrication of large area device with power conversion efficiency (PCE) close to small area device. The device structure of the inverted t-PSC is ITO/ZnO(sol-gel)(30 nm)/P3HT:ICBA(1:1, wfw) (180 nm)/treatment with alcohol/PEDOT:PSS(80 nm)/ZnO nanoparticles (ZnO NP)(25 nm)/Poly({4,8-bis [(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}(3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophenediyl}) (PTB7): PC71BM (1:1.5, w/w)(90 nm) /MoO3(15 nm)/Ag(100 nm). For the small-area (0.02-0.03 cm(2)) device, its PCE can be enhanced form 7.06% to 8.10% by treating with 1-hexanol on P3HT:ICBA surface, resulting from more efficient hole collection for the bottom subcell by the improved film formation of PEDOT:PSS. As the device area is enlarged to 1 cm(2), the PCE can be enhanced from 2.19% to 7.00% by the same alcohol treatment. (C) 2014 Elsevier B.V. All rights reserved.