Highly ordered mesoporous carbon for mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cell

Highly ordered mesoporous carbon (OMC) with well-connected frameworks was applied in mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells as counter electrode. The OMC were synthesized by a template method and mixed with flaky graphite to prepare the carbon paste, which was used to fabricate the counter electrode by screen-printing technology. The OMC based solar cell presented a fill factor (FF) of 0.63 and a power conversion efficiency (η) of 7.02%, which was a remarkable improvement compared with the carbon black based device. The electrochemical impedance spectrum measurement demonstrated that the uniform mesopores and interconnected structures in the carbon counter electrode promoted the decrease of charge transfer resistance at the interface and thereby the higher FF and η was obtained.