| Summary: | 博士 === 國立臺灣科技大學 === 電子工程系 === 105 === The mechanism of the open-circuit voltage (VOC) in organic photovoltaic (OPV) devices still under debated. Although several groups have dedicated to controlling and improving VOC, the physical understanding still lacks. This thesis develops a new and simple approach for analyzing VOC. By using the reduced spectra which proposed by Vandewal et al. and employing a home-made measurement system, the mechanism of VOC is thoroughly studied.
The first step of this thesis is to set up a measurement system for observing the electroluminescence (EL) of OPV devices. With the aid of external quantum efficiency (EQE) spectrum, the characteristics of the charge-transfer (CT) states can be deduced from the reciprocity relation of EL and EQE which proposed by Rau. The CT energy, reorganization energy, electronic coupling matrix element, and energetic losses can be simultaneously calculated using the proposed approach. Several features of the CT states in determining VOC were systematically studied, including the molecular packing, intermolecular interaction, morphology, injection barrier at the interface, and chemical structure. The final stage summarizes the factors influencing VOC by relating the CT characteristics to VOC. The above results can lead to an in-depth understanding in VOC of small-molecule OPV devices. Concurrently, the information can be used for developing high-VOC materials. Therefore, the thesis benefits the researches focusing on the improvement in VOC and the development of the device efficiency.
|
|---|
