Atomic force photovoltaic microscopy

A new conductive atomic force microscopy (AFM) technique, called atomic force photovoltaic microscopy, has been developed to characterize localized variations in the performance of organic photovoltaic devices. The technique works by illuminating microscopic solar cells with either broadband or narrowband light sources while injecting them with current through a conductive AFM probe. Sample biases ranging from -20V to +15 V have been applied in combination with simple lamps, lasers, and solar simulated light to generate current ranging from <1 pA to nearly 1 μ A. Simultaneous topographic and current maps are generated, and IV characteristics (including key figures of merit such as power conversion efficiency) can be determined for single cells. Preliminary data including evidence of localized variations in open circuit voltage are presented.