Imaging Organic Solar Cell Morphology with Organic Light Emitting Diode-Organic Solar Cell Devices

Organic solar cell (OSC)-organic light emitting Diode (OLED) stacked structures are investigated for their use in imaging the morphology of the bulk heterojunction layer used in OSCs. In lieu of the top cathode, bilayer OLED devices can be deposited directly on top of the otherwise traditional OSC device. Design considerations and device optimization are detailed. Results show that the bulk heterojunction layer composed of a blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) is sufficiently hole-conductive to allow for reasonably strong emission, peaking at a brightness of 175 cd/m(2) at a driving voltage of 8.5V and a current density of 12.5mA/cm(2). Since the OLED is in intimate contact with the P3HT:PCBM layer, it provides enhanced images of the bulk heterojunction with information on macro-scale defects and morphological variations. By tuning the emission intensity, detailed images can be obtained without the need for overly sensitive or costly cameras. Further applications of this technique, such as its potential in testing new donor polymer formulations as well as its capacity to monitor degradation due to residual solvents, are briefly discussed.