Preparation of ZnO/NiO-loaded flexible cellulose nanofiber film electrodes and their application to dye-sensitized solar cells oleh Getachew Feyissa Gemeda, Habtamu Fekadu Etefa, Chin-Chih Hsieh, Mekuriaw Assefa Kebede, Toyoko Imae, Yee-Wen Yen