Local Performance Evaluation of Organic Solar Cell Using Scanning Tunneling Microscopy (STM)

Abstract

　Light-modulated scanning tunneling spectroscopy (LM-STS) was applied to evaluating spatial variation of the local generation efficiency in an organic solar cell (OSC) with a bulk heterojunction (BHJ) structure. The acquired surface morphology and microscopic current-voltage (J-V) characteristics under dark and illuminated conditions allowed us to map not only the potential, i.e. the open-circuit voltage (V_OC) but also the short-circuit current (J_SC), fill-factor (FF) and internal resistance of the OSC on a scanning tunnel microscopy (STM) surface morphology. Understanding the device level macroscopic J-V characteristics of OSC's from the individual nanoscale J-V characteristics will be the key issue to develop new OSC devices with superior performances.