Morphological Characterization

The performance of organic electronic devices is profoundly influenced by the nanoscale morphology of the organic film. For example, the active layer of a bulk heterojunction organic photovoltaic (BHJ OPV) device is a ~100 nm thick film consisting of a blend of an electron donating and electron accepting material that phase segregates to form nanoscale, bicontinuous domains. The size, purity, order, and distribution of these nanoscale domains all affect each of the processes that govern solar cell efficiency. Therefore, having control over nanoscale morphology is of great importance.

Given the complicated nature of organic thin films, no one technique can fully describe the nanoscale morphology. In order to probe the nanoscale morphology of organic films, we employ a variety of different characterization techniques. By utilizing a variety of different techniques, we can more completely describe a given system in order to develop structure-property-processing relationships that will guide the development of future materials and devices. By comparing the nanoscale morphology of related OPV systems that perform differently, we can identify morphological characteristics that either help or hurt device performance, and then tune our fabrication procedures accordingly. The figure below is an example of how the nanoscale morphology of an organic film (in this case a small molecule donor:fullernene acceptor BHJ OPV) can be studied with several different techniques, which each provide unique structural information about the system.