Natural chlorophyll is easily decomposed by heat, light, acid and alkali, and insoluble in water, so its application is limited. Therefore, the structure of natural chlorophyll was modified to make it a stable metalloporphyrin structure. The application fields of metalloporphyrins have been expanding and attracted much attention. As a kind of metalloporphyrin, sodium copper chlorophyllin has high stability, and metalloporphyrin is widely used as food additive, cosmetic additive, colorant, medicine, photoelectric conversion material and other fields. Chlorophyll copper sodium salt is transformed from chlorophyll, and natural chlorophyll has two structures, which makes its copper sodium salt have more complex components and structures. In practice, the expression of copper sodium salt only by molecular formula has its shortcomings compared with its wide application. As a metalloporphyrin, sodium copper chlorophyllin has attracted special attention. The development of organic dye-sensitized semiconductor photovoltaic cells with wide band gap began in the 1990s. The photoelectrode of dye-sensitized photoelectrochemical substrate model includes a porous semiconductor with wide band gap and large surface area, and the surface of which is adsorbed with dyes sensitive to visible spectrum. Due to the characteristics of ultra-particle film (UPF), such as large surface area and porosity, the research on constructing efficient photoelectrochemical substrate on UPF crystal electrode has made rapid progress. Some researchers have prepared the photoelectrochemical substrate model of SnO2 ultrafine film, using sodium copper chlorophyllin as sensitizer and I-/I 3- as redox pair, and designed and fabricated the photoelectrochemical substrate with sandwich structure, and studied its photoelectric conversion mechanism.
Specific steps
1, ultrafine particle film adsorption of organic dyes
Dissolve excessive paste-like sodium copper chlorophyllin in anhydrous ethanol, and filter to obtain bright green solution. The conductive glass deposited with SnO2 UPF was soaked in this solution for 48 hours, and then taken out and dried.
2. Fabrication of photoelectrochemical substrate
The photoelectrochemical substrate is mainly composed of three parts: photoelectrode, electrolyte layer and collector, which is similar to sandwich structure. The photoelectrode is prepared by plating a layer of semiconductor UPF on conductive glass by direct current gas discharge activation reaction evaporation deposition method, and adsorbing light-sensitive dye molecules on UPF. Electrolyte contains redox couple, which is the bridge between photoelectrode and collector and the way of hole transfer in battery circuit. The collector is the place where the redox pair that has lost electrons in the electrolyte regains electrons, and it must have good conductivity. The insulated enameled wire separates the photoelectrode from the collector, keeping a certain distance between them and making the electrolyte have a certain space. Silver wires with strong conductivity are fixed on the photoelectrode and collector respectively through conductive silver glue to connect with external circuits to measure their open-circuit voltage and short-circuit current. The normal incidence of incident light through the collector is defined as normal incidence, and the normal incidence of incident light through the photoelectrode is defined as reverse incidence.
The photosensitizer sodium copper chlorophyllin absorbs light and is activated, then the activated sensitizer emits an electron to the conduction band of SnO2 semiconductor, and the oxidized sensitizer is reduced by subsequent redox. Subsequently, this successor molecule gets electrons from the collector and returns to neutrality. As a result, in the case of open circuit, the two electrodes will generate photoelectric potential, and if they are connected by an appropriate external circuit, there will be a response photocurrent.