Fenilsiyanovinilbenzoik asit ve akridin içeren bileşiklerin duyarlaştırıcı boya olarak güneş hücrelerinde kullanımı
Application of phenylcyanovinylbenzoic acid and acridine containing compounds as sensitizer dyes in solar cells
- Tez No: 1017068
- Danışmanlar: PROF. DR. İLKAY ŞİŞMAN
- Tez Türü: Yüksek Lisans
- Konular: Enerji, Kimya, Energy, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: Sakarya Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimya Ana Bilim Dalı
- Bilim Dalı: Analitik Kimya Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
Fosil yakıtların çevresel etkileri ve sınırlı rezervleri, temiz ve sürdürülebilir enerji kaynaklarına geçişi hızlandırmıştır. Bu bağlamda güneş enerjisi, yüksek potansiyeliyle öne çıkarken, boya duyarlı güneş hücreleri (BDGH) düşük maliyet, basit üretim ve düşük ışık koşullarında kararlı performans gibi avantajlar sunar. Bu çalışmada, fenilsiyanovinilbenzoik asit bağlayıcı grup ve akridin π-köprüsü içeren, D-π-A-π-A yapısına sahip iki yeni metal içermeyen organik boya (BIM29 ve BIM30) sentezlenmiş ve BDGH'lerde duyarlaştırıcı olarak kullanılmıştır. Her iki boya trifenilamin donörü taşımakta; yardımcı akseptör olarak BIM29'da benzotiyadiazol, BIM30'da benzotriazol bulunmaktadır. Sentezlenen boyalar FT-IR, 1H/13C NMR ve LC-MS ile doğrulanmıştır. UV-Vis ölçümlerinde BIM29, THF çözeltisinde 417 nm; BIM30 ise 415 nm'de maksimum absorpsiyon göstermiştir. BIM30'un görünür bölgede molar absorpsiyon katsayısı (ε = 2,11 × 10⁴ M⁻ ¹ cm⁻ ¹), BIM29'a (ε = 0,73 × 10⁴ M⁻ ¹ cm⁻ ¹) göre yaklaşık üç kat yüksektir. Optik bant aralığı enerjileri sırasıyla 2,53 eV (BIM29) ve 2,49 eV (BIM30) olarak hesaplanmıştır. CV ile belirlenen HOMO seviyeleri (BIM29: 0,91 V; BIM30: 0,90 V vs. NHE) birbirine yakın olup, LUMO seviyeleri (BIM29: −1,62 V; BIM30: −1,59 V vs. NHE) TiO2 iletim bandına göre daha negatiftir; bu da elektron enjeksiyonu ve elektrolitle rejenerasyon için yeterli termodinamik etkiyi doğrular. Fotovoltaik performans optimizasyonunda çözücü, daldırma süresi, TiO2 anot yapısı ve kenodeoksikolik asit (CDCA) ortak-adsorbanı sistematik olarak incelenmiştir. THF, DCM'ye kıyasla daha yüksek performans sağlamıştır. Optimum daldırma süreleri BIM29 için 7 saat, BIM30 için 3 saat olarak bulunmuştur. Anot karşılaştırmasında T/T (şeffaf/şeffaf) yapı, T/D (şeffaf/dağıtıcı) yapıya üstün gelmiştir. CDCA çalışmaları, BIM30'un agregasyon eğiliminin daha yüksek olduğunu ve CDCA ilavesiyle etkin şekilde bastırılabildiğini göstermiştir. Optimum koşullar altında (BIM29: THF, 7 saat, T/T, 0,1 mM CDCA; BIM30: THF, 3 saat, T/T, 0,3 mM CDCA) BIM29 bazlı BDGH, Jsc = 6,81 mA cm⁻ ², Voc = 0,675 V, FF = 0,67 ve η = %3,08; BIM30 bazlı BDGH ise Jsc = 7,82 mA cm⁻ ², Voc = 0,684 V, FF = 0,67 ve η = %3,58 değerlerine ulaşmıştır. BIM30'un verimdeki %16,2'lik üstünlüğü, daha yüksek molar absorpsiyon (özellikle 415 nm'de ~%189 göreli artış), CDCA ile agregasyon kontrolü ve arayüz dinamiklerindeki iyileşmelerle ilişkilendirilmiştir. IPCE sonuçları her iki boyanın da 350–500 nm aralığında etkili foton-akım dönüşümü sergilediğini göstermiştir. EIS analizlerinde BIM30'un daha yüksek yük rekombinasyon direnci (Rrec = 90 Ω) ve daha uzun elektron ömrü (τe = 0,68 ms; BIM29: 0,44 ms) elde edilmiş; bu da rekombinasyon kayıplarının azaldığını ve Voc artışını desteklemiştir. Sonuç olarak, yardımcı akseptör seçiminin BDGH performansını belirgin şekilde etkilediği gösterilmiştir. Benzotriazol içeren BIM30, benzotiyadiazol içeren BIM29'a kıyasla daha yüksek ışık hasadı, daha etkin agregasyon baskılanması, daha uzun elektron ömrü ve daha yüksek rekombinasyon direnci sayesinde üstün fotovoltaik performans sunmuştur. Bulgular, fenilsiyanovinilbenzoik asit ve akridin içeren D-π- A-π-A boyaların etkili duyarlaştırıcılar olduğunu ve moleküler tasarımda yardımcı akseptör mühendisliğinin kritik bir rol oynadığını ortaya koymaktadır.
Özet (Çeviri)
The increasing global demand for energy, combined with the environmental problems caused by the excessive use of fossil fuels, has accelerated the search for sustainable and renewable energy sources. Fossil fuel consumption is associated with serious environmental consequences, including greenhouse gas emissions, climate change, and air pollution. Moreover, the limited availability of fossil fuel reserves highlights the urgent need for alternative energy technologies that are both environmentally friendly and economically feasible. Among the various renewable energy sources, solar energy is considered one of the most promising options due to its abundance, sustainability, and minimal environmental impact. Consequently, significant research efforts have been directed toward the development of efficient photovoltaic technologies capable of converting solar energy into electricity. Dye-sensitized solar cells (DSSCs) represent an important class of photovoltaic devices that have attracted considerable attention since their first introduction. Compared with conventional silicon-based solar cells, DSSCs offer several advantages, such as relatively low production cost, simple fabrication procedures, mechanical flexibility, and good performance under diffuse or low-light conditions. These characteristics make DSSCs particularly suitable for indoor energy harvesting and emerging photovoltaic applications. A typical DSSC consists of a semiconductor photoanode, usually based on nanocrystalline titanium dioxide (TiO₂), a sensitizing dye molecule responsible for light absorption, an electrolyte that regenerates the oxidized dye, and a counter electrode that completes the electrical circuit. Among these components, the sensitizing dye plays a crucial role in determining the overall performance of the device because it is responsible for capturing sunlight and initiating the electron injection process. In recent years, extensive research has focused on the design and development of new sensitizer molecules with improved optical and electrochemical properties. Initially, ruthenium-based metal complexes dominated DSSC research due to their excellent photophysical characteristics and relatively high power conversion efficiencies. However, the high cost, limited availability, and environmental concerns associated with metal-based dyes have encouraged researchers to explore alternative sensitizer materials. As a result, metal-free organic dyes have emerged as promising candidates for DSSC applications. These dyes offer several advantages, including high molar extinction coefficients, structural flexibility, tunable electronic properties, and relatively simple synthetic routes. Furthermore, the molecular structures of organic dyes can be systematically modified in order to optimize their lightharvesting capabilities and charge-transfer properties. One of the most widely used molecular design strategies for organic sensitizers is the donor–π–acceptor (D–π–A) architecture. In this configuration, an electron-donating group is connected to an electron-accepting anchoring group through a conjugated π- bridge. Upon light absorption, intramolecular charge transfer occurs from the donor to the acceptor unit, facilitating efficient electron injection into the conduction band of the semiconductor. In order to further enhance charge separation and broaden the absorption spectrum, more advanced molecular architectures such as donor–π– acceptor–π–acceptor (D–π–A–π–A) structures have been proposed. These structures incorporate additional electron-withdrawing units that can improve the electronic communication within the molecule and enhance photovoltaic performance. In this study, two new metal-free organic dyes, designated as BIM29 and BIM30, were designed and synthesized based on a D–π–A–π–A molecular framework. Both dyes contain a triphenylamine unit as the electron donor, which is widely used in DSSC sensitizers due to its strong electron-donating ability and favorable charge transport properties. An acridine moiety was employed as the π-bridge in order to extend the conjugation length and promote efficient charge transfer. In addition, phenylcyanovinylbenzoic acid was used as the anchoring group to ensure strong adsorption of the dye molecules onto the TiO₂ surface. The main structural difference between the two dyes arises from the auxiliary acceptor unit incorporated into the molecular backbone. In BIM29, benzothiadiazole was used as the auxiliary acceptor, while in BIM30 benzotriazole served as the auxiliary acceptor. The incorporation of different auxiliary acceptor groups was expected to influence the optical absorption characteristics, electronic energy levels, intermolecular interactions, and overall photovoltaic performance of the dyes. Following synthesis, the molecular structures of the dyes were confirmed through a combination of spectroscopic and analytical techniques. Fourier transform infrared spectroscopy (FT-IR) was used to identify the characteristic functional groups present in the molecules. Proton and carbon nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR) provided detailed structural information and confirmed the successful formation of the target compounds. In addition, liquid chromatography–mass spectrometry (LC-MS) analysis verified the molecular masses of the synthesized dyes, further supporting the proposed molecular structures. The optical properties of BIM29 and BIM30 were investigated using UV–Vis absorption spectroscopy in tetrahydrofuran (THF) solution. The absorption spectra revealed that BIM29 exhibits two main absorption maxima at 292 nm and 417 nm, while BIM30 shows absorption maxima at 353 nm and 415 nm. These absorption bands correspond to π–π* transitions and intramolecular charge transfer processes within the conjugated dye structures. An important difference between the two dyes was observed in their molar extinction coefficients. BIM30 displayed a significantly higher molar absorption coefficient in the visible region (ε = 2.11 × 10⁴ M⁻¹ cm⁻¹) compared with BIM29 (ε = 0.73 × 10⁴ M⁻¹ cm⁻¹). This result indicates that BIM30 possesses a stronger light-harvesting capability, which is expected to enhance photocurrent generation in DSSC devices. The optical band-gap energies of the dyes were determined from the onset of their absorption spectra. The calculated band-gap values were 2.53 eV for BIM29 and 2.49 eV for BIM30, suggesting relatively similar electronic structures. To further investigate the electrochemical properties of the dyes, cyclic voltammetry measurements were performed. The HOMO energy levels were determined to be 0.91 V for BIM29 and 0.90 V for BIM30 versus the normal hydrogen electrode (NHE). The LUMO energy levels were calculated as −1.62 V for BIM29 and −1.59 V for BIM30 versus NHE. These values indicate that the excited-state energy levels of both dyes are sufficiently negative relative to the conduction band edge of TiO₂, allowing efficient electron injection into the semiconductor. At the same time, the HOMO levels are appropriately positioned to enable regeneration of the oxidized dye molecules by the iodide/triiodide redox electrolyte. In order to optimize the photovoltaic performance of DSSC devices, several experimental parameters were systematically investigated. These parameters included the solvent used for dye adsorption, the dye-loading time, the architecture of the TiO₂ photoanode, and the use of a co-adsorbent molecule. The choice of solvent can strongly influence dye aggregation and adsorption behavior on the TiO₂ surface. Comparative experiments showed that tetrahydrofuran (THF) provided better device performance than dichloromethane (DCM), likely due to improved dye dispersion and more uniform adsorption on the semiconductor surface. The dye adsorption time was also optimized to achieve sufficient surface coverage without excessive aggregation. The optimal immersion time was determined to be 7 hours for BIM29 and 3 hours for BIM30. Longer immersion times did not result in further improvement and in some cases led to decreased device performance due to increased dye aggregation. Another important factor affecting DSSC efficiency is the architecture of the TiO₂ photoanode. Two different configurations were examined in this study: a transparent/transparent (T/T) structure and a transparent/scattering (T/D) structure. The experimental results indicated that the T/T configuration provided better photovoltaic performance for both dyes, suggesting more efficient charge transport and reduced recombination losses in this configuration. The influence of the co-adsorbent chenodeoxycholic acid (CDCA) was also investigated. Co-adsorbents are commonly used in DSSC systems to reduce dye aggregation on the TiO₂ surface and improve the uniformity of dye coverage. The results showed that BIM30 exhibited a higher tendency to aggregate on the semiconductor surface compared to BIM29. However, the addition of CDCA effectively suppressed this aggregation behavior and significantly improved the device performance. The optimal CDCA concentrations were determined to be 0.1 mM for BIM29 and 0.3 mM for BIM30. Under the optimized conditions, the DSSC fabricated with BIM29 as the sensitizer exhibited a short-circuit current density (Jsc) of 6.81 mA cm⁻², an open-circuit voltage (Voc) of 0.675 V, a fill factor (FF) of 0.67, and a power conversion efficiency (η) of 3.08%. In comparison, the DSSC device based on BIM30 showed improved photovoltaic parameters, including a Jsc value of 7.82 mA cm⁻², a Voc of 0.684 V, an FF of 0.67, and an overall efficiency of 3.58%. The approximately 16.2% increase in efficiency observed for the BIM30-based device can be attributed to several factors. First, the higher molar extinction coefficient of BIM30 in the visible region enhances light absorption and photocurrent generation. Second, the aggregation behavior of BIM30 can be effectively controlled by the addition of CDCA, resulting in improved dye organization on the TiO₂ surface. Finally, improved interfacial charge transfer dynamics contribute to reduced recombination losses. Incident photon-to-current conversion efficiency (IPCE) measurements revealed that both dyes exhibit effective photoresponse within the wavelength range of 350–500 nm, which corresponds well with their optical absorption spectra. In addition, electrochemical impedance spectroscopy (EIS) analysis was conducted to investigate the charge transport and recombination processes occurring within the DSSC devices. The EIS results showed that the BIM30-based device exhibits a higher recombination resistance (Rrec = 90 Ω) compared to the BIM29-based device. Furthermore, the electron lifetime in the TiO₂ photoanode was found to be longer for BIM30 (τe = 0.68 ms) than for BIM29 (τe = 0.44 ms). These findings indicate that BIM30 effectively suppresses charge recombination at the TiO₂/electrolyte interface, which contributes to improved device performance and a slightly higher open-circuit voltage. In conclusion, the results of this study demonstrate that the molecular design of the auxiliary acceptor plays a significant role in determining the photovoltaic performance of metal-free organic dyes in DSSC systems. The benzotriazole-based dye BIM30 exhibited superior performance compared to the benzothiadiazole-based dye BIM29 due to its enhanced light-harvesting capability, better control of aggregation, longer electron lifetime, and higher recombination resistance. These findings highlight the importance of auxiliary acceptor engineering in the design of efficient organic sensitizers and provide valuable insights for the future development of high-performance DSSC materials.