Recent studies have reported that a thin interlayer between poly(3, 4-ethylene dioxythiophene)-poly(styrene sulfonic acid) (PEDOT: PSS) and an emissive polymer layer leads to a large increase in the performances of polymer light-emitting diodes (PLEDs) by preventing significant quenching of the radiative excitons at the PEDOT: PSS interface; therefore, acting as an efficient exciton-blocking layer. Using the similar idea, a thin interlayer was fabricated between PEDOT: PSS and the active layer of conjugated polymers/methanofullerene composites in a plastic solar cell. The interlayer consisted of a poly(fluorene)-based hole transporter spin-coated directly on top of the PEDOT: PSS layer. The devices with the interlayer exhibited a higher efficiency than in those without the interlayer. (c) 2007 Elsevier B.V. All rights reserved.