[Enhanced V(oc) in photovoltaic cell by electrodeposited polythiophene thin film].

Poly(3-hexylthiophene) (P3HT) thin films were electrochemically deposited directly on indium tin oxide (ITO)/poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT : PSS) substrates. Its optical absorption peak is located at about 410 nm and tailing to 610 nm, corresponding to 2.04 eV of bandgap. Its highest occupied molecular orbital (HOMO) energy is -5.21 eV, while the HOMO energy of the chemically synthesized P3HT is -5.02 eV. The lower HOMO energy of the electrodeposited P3HT may be attributed to the enhancement of regularity. The morphology of the P3HT thin film characterized by atomic force microscopy (AFM) indicates that the molecules contact firmly. The cyclic voltammetry results show that its electrochemical property is stable. The authors prepared photovoltaic cell with the P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the active layer. Because of the lower HOMO of the electrodeposited P3HT, the open circuit voltage (V(oc)) of the device is up to 0.76 V, indicating a new way to enhance the V(oc) of the organic photovoltaic cells.