RC-Constant in Organic Photodiodes Comprising Electrodes With a Significant Sheet Resistance

Organic photodiodes provide prospects for the fabrication of arbitrarily shaped photodetectors. However, the enlarged detection area in conjunction with their minuscule absorber layer thickness increases the capacitance of these devices when compared with convential silicon photodiodes. The mandatory transparency of at least one electrode can, so far, only be provided by materials with significant sheet resistances. These factors lead to nonnegligible RC-constants where high frequency signal detection is ultimately RC-limited. In this letter, we devise a method to determine the effective RC-constant for an extended rectangular device comprising electrodes with a significant sheet resistance and show that it is up to 59% smaller than estimated from the geometric device dimensions.