In the letter, a conductor/insulator/semiconductor (CIS) polymer solar cell was demonstrated with higher performance and stability than standard polymer solar cell. The random copolymer, poly(styrene-co-methyl-methacrylate) (PS-r-PMMA), was used as the insulator. By control the annealing temperature, a 2 nm-thick insulator could provide dark current suppress function and ensure carrier tunneling simultaneously. The efficiency of the CIS solar cell was improved from 2.09 to 2.37%, around 11% improvement. Meanwhile, the half-efficiency lifetime increase from 58 to 97 h by the applying of PS-r-PMMA protection layer. (C) 2010 Elsevier B.V. All rights reserved.