A simple but efficient method has been first developed for the solution preparation of CrO x as anode buffer layer for polymer photovoltaic cells. The chromium acetylacetonate precursor can be transformed into CrO x upon thermal annealing at ∼60 °C, followed by ultraviolet-ozone treatment. The leakage current of the device with the CrO x anode buffer layer was decreased, and short-circuit current density (J sc) was significantly increased in comparison with the device with the traditional poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PE-DOT:PSS) buffer layer. By analyzing the current density− voltage characteristics of the device, it is found that the CrO x anode buffer layer can simultaneously decrease the series resistance and increase the parallel resistance of the device, in comparison with the device with PEDOT:PSS anode buffer layer. For the cells based on poly(3-hexylthiophene) (P3HT) as donor and (6,6)-phenyl-C 61 -butyric acid methyl ester (PCBM) as acceptor, the power conversion efficiency (PCE) can be improved from 3.71% (with PEDOT:PSS buffer) to 4.27% via introduction of CrO x buffer layer. The PCE of the device based on P3HT as donor and indene-C 60 -bisadduct (ICBA) as acceptor with CrO x anode buffer layer was further increased from 6.08 (with PEDOT:PSS buffer) to 6.55%. The results indicate that CrO x is a promising anode buffer layer for efficient and stable polymer solar cells.