Performance improvement of polymer solar cells using SWCNT as a buffer layer and solvent engineering

Single-walled carbon nano tube (SWCNT) is used as a buffer layer to improve the performance of polymer solar cells. The buffer layer is located between the active layer and the cathode electrode in the solar cell structure such as PET/ITO/PEDOT:PSS/MEH-PPV:C60 (1:2)/SWCNT/Al. SWCNTs act as tunnels to help electron collection by cathode electrode, prevent the randomly movement of electrons, leading to the reduction of recombination at the interfaces after dissociation. By implementing this method, the short circuit current (J_sc) of fabricated solar cells increases from 20% to 40% depending on the solvent and the open circuit voltage (V_oc) reduces slightly. Since the type of solvent has an important effect on the properties of fabricated solar cells, the active layer was spin coated using three different solvents which were Chlorobenzene, 1, 2-Dichlorobenzene and Toluene. The best performance was achieved for the device fabricated using Chlorobenzene. The resulted output powers using Chlorobenzene, 1, 2-Dichlorobenzene and Toluene were 10.04 µW/cm², 7.59 µW/cm² and 1.74 µW/cm² respectively.