Güneş Pili Uygulamaları İçin Yeni Boyar Maddelerin Sentezi ve Karakterizasyonu
Thesis Type: Doctorate
Institution Of The Thesis: Yildiz Technical University, Faculty of Arts & Science, Department of Chemistry, Turkey
Approval Date: 2022
Thesis Language: Turkish
Student: Burak Yıldız
Supervisor: Muhammet Kasım Şener
Open Archive Collection: AVESIS Open Access Collection
Abstract:Dye-sensitized solar cells (DSSCs) are an important technology for solar energy conversion due to their low production cost and adjustable esthetic properties such as color and transparency. The dye molecule, an essential component of dye-sensitized solar cells, collects solar photons and is excited. The excited dye molecule initiates the charge separation process by injecting electrons into the conduction band of the metal oxide. Phthalocyanines are used as dyes in dye-sensitized solar cells because of their absorption in the red/near-infrared region and their thermal and chemical stability. In recent years, asymmetric phthalocyanines containing carboxylic acid in particular have been used in dye-sensitized solar cells. The carboxylic acid ensures that the dye molecules adhere to the metal oxide surface. However, phthalocyanine-sensitized dyes detach from the metal oxide surface over time, which reduces the long-term stability of the solar cells. In order to increase the long-term stability and photovoltaic performance of solar cells, attempts have been made in recent years to find new functional groups as an alternative to carboxylic acid that allow the dye to adhere to the metal oxide surface. This thesis consists of three different published studies, including the synthesis of new asymmetric phthalocyanine derivatives containing pyrazole carboxylic acid as an alternative to carboxylic acid that can be used in dye-sensitized solar cells and the study of their photovoltaic properties. In the first study, asymmetric zinc phthalocyanine was synthesized using phthalonitrile derivatives of oxygen-bridged pyrazolecarboxylic acid in the form of ethyl ester and 4-tert-butylphthalonitrile. The obtained ester form zinc phthalocyanine was then hydrolyzed, and the pyrazolecarboxylic acid derivative used as an anchor group was synthesized (PCA-ZnPc-1). The structures of the synthesized compounds were characterized by spectroscopic methods. Dye-sensitized solar cells (DSSCs) were used with the appropriate compound, and a power conversion efficiency (PCE) of about three times was obtained compared to the asymmetric phthalocyanine samples in the literature, which have the same structure and use carboxylic acid derivatives as the anchor group. Besides this increase,the maximum power conversion efficiency was achieved by immersing the semiconductor coated glass in the dye solution for only 2 hours. In the second study, the same anchor group was used, but instead of 4-tert-butylphthalonitrile, a phthalonitrile derivative with two hexylsulfanyl groups in the peripheral position was used. The main purpose was to observe how positively the asymmetric phthalocyanine affects the energy conversion efficiency by shifting the maximum wavelength of the asymmetric phthalocyanine due to the effect of the S atom and the electron donating CH2 groups. A red shift of 25 nm was observed in the measurements. When the related compound was applied in dye-sensitized solar cells, an increase in the energy conversion efficiency of about 30 % was observed compared to the derivative with the 4-tert-butyl group. In addition, measurements of hydrogen production by photoelectrochemical water splitting were performed in this study. In the third study, the linking group was the same, and a phthalonitrile derivative containing bulky 2,6-diphenylphenol in the peripheral positions was used in the synthesis of the asymmetric phthalocyanine, since there are many examples of this in the literature and the maximum energy conversion efficiency was achieved by reducing aggregation through the use of bulky groups. The structures of the new compounds were characterized by spectroscopic methods. The energy conversion efficiency of the phthalocyanine compound increased by about 53 % compared to the asymmetric phthalocyanine derivative with the 4-tert-butyl group and by about 18% compared to the derivative with the hexylsulfanyl group.