Spectral conversion technology based on NaYF4:Yb3+, Er3+ upconversion nanoparticles was extensively used to improve photovoltaic conversion efficiency of solar cells. However, the response mismatch between absorption of semiconductors and upconversion luminescence (UCL) limits the application of spectral conversion technology. Nonstoichiometric WO2.72 nanoparticles display the broad absorption from visible to near-infrared region due to the presence of oxygen vacancy, which is overlapped with the UCL of NaYF4:Yb3+, Er3+ nanoparticles. Thus, the combination between NaYF4:Yb3+, Er3+ nanoparticles, and nonstoichiometric WO2.72 provides a possibility for designing a novel UCL spectral converted solar cells. In this work, composite film consisted of NaYF4:Yb3+, Er3+ nanoparticles, and WO2.72 nanofibers was prepared. The UCL of NaYF4:Yb3+, Er3+/WO2.72 film was decreased in contrast to pure NaYF4:Yb3+, Er3+ nanoparticles due to energy transfer from NaYF4:Yb3+, Er3+ nanoparticles to WO2.72 nanofibers. The NaYF4:Yb3+, E3+/WO(2.72)film exhibits the photocurrent generation upon the 980 nm excitation. This novel UCL spectral converted solar cells based on the broad absorption of defects in the WO2.72 host will provide a novel view for photovoltaic devices.