Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.Nghiên cứu cấu trúc và tính chất một số hệ vòng ngưng tụ chứa lưu huỳnh và silic ứng dụng trong chế tạo vật liệu quang điện.MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF EDUCATION TRAN NGOC DUNG Study on the structure and properties of some sulfur and silicon containing fused rings applied in the fabrication of ph.
MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF EDUCATION TRAN NGOC DUNG Study on the structure and properties of some sulfurand silicon-containing fused rings applied in the fabrication of photovoltaic materials Specialization: Theoretical and Physical Chemistry Code: 9.44.01.19 SUMMARY OF CHEMICAL PhD THESIS HÀ NỘI – 2022 The thesis was completed at: Department of Chemistry - Hanoi University of Education Scientific Instructors: Assoc Prof Dr Nguyen Thi Minh Hue Assoc Prof Dr Nguyen Hien Review 1: Prof Tran Thi Nhu Mai Hanoi University of Sciences – Vietnam National University, Hanoi Review 2: Prof Pham Cam Nam University of Science and Technology – The University of Danang Review 3: Prof Nguyen Thanh Tung Institute of Materials science – Vietnam Accademy of Science and Technology The thesis will be presented to the Board of thesis review at Hanoi University of Education on .h day month year The thesis can be found at: National Library, Hanoi or the library of Hanoi National University of Education LIST OF WORKS PUBLISHED BY AUTHOR 1) Nguyen Van Trang, Tran Ngoc Dung, Tran Thi Thoa, Dinh Thi Mai Thanh, and Nguyen Thi Minh Hue "Stability and Semi‐Conductive Property of Some Derivatives of Mono‐and Di‐Silole: A Theoretical Study." Vietnam Journal of Chemistry 57, no (2019): 507-13 2) Tran Ngoc Dung, Nguyen Van Trang, Dinh Thi Mai Thanh, Nguyen Thi Van Khanh, Hien Nguyen, and Hue Minh Thi Nguyen "A Facile Regioselectively Synthesis of 2-Alkenylbenzo [1, 2-B: 4, 5-B’] Dithiophene by Pd/Cu/Ag-Catalyzed Ch Functionalization." ChemistrySelect 5, no 19 (2020): 5581-86 3) Tran Ngoc Dung, Nguyen Van Trang, Tran Thi Thoa, Phan Thi Thuy, Dinh Thi Mai Thanh, and Nguyen Thi Minh Hue "Theoretical Study of Structures and Properties of Some Silole Compounds." Vietnam Journal of Chemistry 58, no (2020): 212-20 4) Nguyen Van Trang, Tran Ngoc Dung, Ngo Tuan Cuong, Le Thi Hong Hai, Daniel Escudero, Minh Tho Nguyen, and Hue Minh Thi Nguyen "Theoretical Study of a Class of Organic D-Π-a Dyes for Polymer Solar Cells: Influence of Various Π-Spacers." Crystals 10, no (2020): 163 5) Nguyen Van Trang, Tran Ngoc Dung, Long Van Duong, My Phuong Pham-Ho, Hue Minh Thi Nguyen, and Minh Tho Nguyen "Structural, Electronic, and Optical Properties of Some New Dithienosilole Derivatives." Structural Chemistry 31, no (2020): 2215-25 6) Nguyen Van Trang, Nguyen Minh Tam, Tran Ngoc Dung, and Minh Tho Nguyen "A Theoretical Design of Bipolar Host Materials for Blue Phosphorescent Oled." Journal of Molecular Graphics and Modelling 105 (2021): 107845 7) Hue Minh Thi Nguyen, Tran Ngoc Dung, Nguyen Van Trang, Ngo Tuan Cuong, Nguyen Van Minh, Hien Nguyen, and Minh Tho Nguyen "Design of Fused Bithiophene Systems Containing Silole and Five-Membered Heterocycles for Optoelectronic Materials." Chemical Physics Letters 784 (2021): 139093 INTRODUCTION The reason for choosing topic Organic photovoltaic materials have many advantages over traditional inorganic materials such as low cost, easy fabrication with large surface area and no high temperature required in the production process Organic photovoltaic materials are commonly used in the manufacture of organic light-emitting diodes, organic solar cells, field-effect transistors and sensors Sulfur-containing heterocyclic compounds are one of the important links constituting photovoltaic organic compounds Among them, thiophene ring is the most popular material thanks to its photovoltaic properties and good charge transfer ability The thiophene ring has a pentagonal aromatic ring structure, consisting of a sulfur atom bonded to a butadiene compound The sulfur atom has two unbonded electron pairs, one of which is involved in the formation of aromaticity for the ring The sulfur atom is highly polar because the outermost electrons orbit the large 3s and 3p orbitals, facilitating electron donation and weak bond formation Furthermore, the sulfur atom can increase its oxidation number thanks to the contribution of the 3d orbital Thanks to the high oxidation numbers, the sulfur atom in the thiophene ring can form functional groups containing oxygen atoms and exhibit special photoelectric properties Since 2005, a number of silicon-containing heterocyclic derivatives have been noticed due to their special electron properties In which, the siole ring is focused on research by scientists Silole has a similar structure to thiophene, the sulfur atom in thiophene is replaced by a silicon atom Siliconcontaining heterocycles generally have lower LUMO energies than other heteroatoms, thus leading to a lower HOMO-LUMO gap Therefore, siliconcontaining heterocyclic compounds are expected to give good luminescence and charge transfer performance Therefore, this thesis proposes to investigate a number of condensate systems containing sulfur and silicon to study and compare their photoelectric properties Calculation software and quantum chemistry methods become an effective tool in studying and investigating molecular structures, chemical reaction mechanisms under different conditions Besides, if using modern calculation methods and high basis functions, the results will be very close to the experiment Within the framework of this thesis, quantum chemical calculations will be used to investigate the substance systems, thereby providing orientation for the experimental synthesis process later At the same time, quantum chemical calculations also help to support and explain experiments as well as investigate properties that are difficult to perform under experimental conditions in Vietnam Research purpose and tasks a) Research purpose: Simulating and predicting the relationship between the structure and properties of the condensed cyclic system containing thiophene and siole heterocycles by quantum chemical calculations Based on the calculated results, they will guide the experimental synthesis of optimized structures with superior properties that can be applied to manufacturing photovoltaic devices b) Research tasks: + Experimenting with quantum chemical calculation methods to select the most optimal calculation method applied to the research system + Optimizing the geometric structure of some condensed ring systems containing thiophene and silole heterocycles by the selected quantum chemical calculation method + Determining and evaluating the semiconductor and luminescence properties of condensed ring systems containing thiophene and silole heterocycles + The results obtained from quantum chemical calculations will guide the selection of substituents and conjugate chain structures to create molecules with desired properties + Proposing optimal structures with the most preeminent properties to guide experimental synthesis Scope and object of the study a) Object: Fused heterocyclic organic compounds containing silole, thiophene and derivative functional groups which have potential applications in organic photovoltaic devices b) Scope of research: Theoretical research of the structure and photoelectric properties of compounds based on the density functional method From the results of theoretical research, select and propose potential compounds for experimental synthesis Scientific and practical significance of the thesis - Apply quantum chemical calculations to clarify the relationship between the molecular structure of sulfur- and silicon-containing condensates and the photoelectric properties of the material - Research and design some compounds with better photoelectric properties than existing ones theoretically, thereby making suggestions for the synthesis of photovoltaic organic materials in the future - Using quantum chemical calculations to confirm the products obtained from organic synthesis New points of the thesis - Systematic comparison of bithiophene compounds with different substituents such as thiophene, siole, pyrole, - Replacing the thiophene bridge in the PBDTS-TZNT compound with other condensed heterocycles has improved the light transmission and absorption of the compound, typically the DTS heterocycle - Successfully replaced the AgOCOCF3 reactant with Ag2O in the alkenylation of BDT derivatives, thereby reducing the cost of conducting the reaction while the reaction efficiency remained unchanged Apply computational chemistry to demonstrate the product of the BDT alkenylation reaction 6 The layout of the thesis Introduction: Introducing the reason for choosing the topic, the purpose and tasks of the research, the object and scope of the research, the scientific and practical significance of the thesis and the new points of the thesis Chapter 1: Introduce the theoretical basis including the theoretical basis of photovoltaic materials, the theoretical basis of quantum chemistry on the DFT density functional method Research substance system includes thiophene and silole system Chapter 2: Research methods Research methods include experimental research methods and theoretical research methods Chapter 3: Research results and discussion, including theoretical research results and experimental results of organic synthesis Conclusion: Summarize the outstanding results of the thesis The thesis consists of 135 pages, 24 tables of data, 44 figures, 190 references Introduction: pages; Chapter 1: 34 pages; Chapter 2: 11 pages; Chapter 3: 70 pages Conclusion and recommendations: pages; List of published works: page; References: 13 pages Chapter THEORY BASIS 1.1 Organic photovoltaic material Organic photovoltaic materials are solid substances that exist in the form of molecular crystals or amorphous thin films made up of molecules or polymers containing π bonds, which are mainly composed of carbon and hydrogen In addition, there may be heterogeneous elements such as oxygen, sulfur, nitrogen Organic photovoltaic materials have attracted the attention of scientists thanks to their superior physicochemical properties: i) Low production cost, easy to produce on large scale; ii) capable of making thin, light and flexible devices, iii) easy to customize materials according to the intended use Despite such advantages, these compounds still have certain limitations, especially in terms of strength and electrical conductivity 1.2 Theoretical foundations of quantum chemistry The Schrödinger equation can be solved exactly for one-electron and onenucleus system However, for systems with two or more electrons, exact solution is not possible due to the interaction between electrons and the increase of variables in the wave function The density functional method is proposed to optimize the solution of the Schrödinger equation, especially in the calculation of large and multi-electron systems Unlike wave functionbased methods, this method is based on electron density In this way, the number of variables in the Schrödinger equation is reduced to only 3, thereby saving computation time 1.3 Theoretical basis of synthetic heterocyclic derivation Condensed heterocyclic compounds have attracted the attention of scientists due to their diverse physical and chemical properties for a long time The basis for creating this diversity lies in the diversity of substituents The reactions to add substituents to the existing organic framework are mostly coupling reactions, i.e new carbon-carbon bond formation reactions such as Heck, Suzuki, Sonogoshira, Negishi, Kumada, Stille, Tsuji-Trost reactions Chapter OVERVIEW OF RESEARCH SUBSTANCE SYSTEM AND RESEARCH METHODS 2.1 Overview of the studied compounds The thiophene molecule has a pentagonal aromatic ring structure, consisting of a sulfur atom bonded to a butadiene compound Among the potential compounds for organic photovoltaic materials, thiophene-based compounds represent an irreplaceable role due to their superior photoelectric properties Modulation of the HOMO-LUMO energy of organic photovoltaic materials can be accomplished using thiophene rings or stiff structures with broad π conjugates of thiophene Silole is a heterocyclic compound containing one atom of valence IV silicon, directly bonded to two hydrogen atoms and a butadiene compound The siole molecule has a lower LUMO energy level than other pentacyclic aromatic compounds such as pyrole, furan or thiophene The low LUMO energy level is thought to be caused by the strong interaction between the π* orbital of the butadiene component and the antibonding σ* ortibal of the bond between the silicon atom and the substituent at the silicon atom 2.2 Research methodology overview 2.2.1 Theoretical research method All structures are built based on Gaussview software The initial structural parameters will be optimized by Gaussian 09 software at the Center for Computational Science, Hanoi National University of Education After conducting structure optimization with the functional B3LYP, the structures will be calculated the frequency of oscillations at the appropriate set of basis functions to confirm that the obtained structure is the structure in the ground state From the optimized structure, the properties of charge transmission, UVVis spectrum, will be calculated on Gaussian 09 software, then processed results based on Gaussview and Chemcraft software 2.2.2 Experimental research methods Alkenization of BDT Place the DMSO solvent into the flask, then add one equivalent of BDT, three corresponding alkene equivalents, 10 mol% Pd(OAc)2, 20 mol% Cu(OAc)2 and finally one Ag2O equivalent Then place the magnet bar in the reaction vessel, install the condenser and heat on a magnetic stirrer heated at 100-110 °C for four hours During reaction optimization, the reaction mixture will be checked every 30 by thin plate chromatography The solvent used is a mixture of suitable proportions of n-hexane and ethyl acetate The thin plate will be illuminated with ultraviolet light with two wavelengths 265 nm and 354 nm to monitor the progress of the reaction After the reaction was completed, the product mixture was diluted with ethyl acetate, extracted with distilled water to remove the catalyst and byproducts The solution containing the main product was adsorbed onto the silica gel for purification by column chromatography The column used was 20 × 50 mm with silica gel of 40-230 mesh The solvent used was a mixture of n-hexane and ethyl acetate The product after being purified will be measured by 1H NMR, 13C NMR, HSQC, HBMC and NOESY spectra to confirm the structure 10 Chapter 3: RESEARCH RESULTS AND DISCUSSION 3.1 Research on applied dipole compounds as host materials in secondgeneration OLED Parent compound (M0) Bphen CBP Figure 3.1: The structure of the compounds is studied based on the groups of Cz, DBTa and DBTb, along with the structures of reference compounds including CBP, Firpic, NPB and Bphen as carrier material, emitting material, and hole and electron transport material Twenty-one molecules as carrier materials have been designed by replacing one CH unit with a nitrogen atom in the parent compound (Figure 11 3.1) Our calculation results indicate that different properties, such as triplet energy value and excitation energy S1, MO energy level and charge-carrying capacity are significantly affected when nitrogen atom is introduced into different positions of DBTa, DBTb and Cz rings of the parent compound Table 3.1: The values of HOMO, LUMO energy, ionization energy (IP), electron affinity (EA), hole and electron recombination energy and triplet energy of the studied compounds (eV) Compo und M0 HOMO LUMO IP EA λh λe Δλ ET -5,23 -1,28 -5,38 -1,19 Cz2 -5,41 -1,34 Cz3 -5,46 -1,39 Cz4 -5,35 -1,36 Cz5 -5,31 -1,35 Cz6 -5,28 -1,36 Cz7 -5,41 -1,19 -5,30 -1,60 -5,34 -1,69 D3a -5,31 -1,49 D4a -5,22 -1,57 D5a -5,28 -1,55 D6a -5,23 -1,67 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,2 0,1 0,2 0,1 0,1 0,1 0,2 0,0 0,0 0,0 0,0 0,0 0,0 2,85 D2a 0,1 0,1 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,11 D1a 0,2 0,2 0,3 0,3 0,3 0,3 0,3 0,2 0,4 0,4 0,3 0,3 0,4 0,4 2,77 Cz1 6,3 6,3 6,4 6,4 6,3 6,3 6,3 6,4 6,4 6,4 6,4 6,3 6,3 6,3 12 2,78 2,76 2,79 2,78 2,62 2,69 2,83 2,83 2,92 2,88 2,75 2,76 D7a -5,33 -1,62 D1b -5,31 -1,31 D2b -5,36 -1,35 D3b -5,33 -1,30 D4b -5,24 -1,25 D5b -5,25 -1,26 D6b -5,20 -1,35 D7b -5,36 -1,32 CBP -5,32 -1,23 Firpic -5,42 -1,78 NPB -4,74 -1,17 Bphen -5,98 -1,48 6,4 6,4 6,4 6,4 6,3 6,3 6,3 6,4 6,2 6,6 5,7 7,3 13 0,4 0,3 0,4 0,3 0,3 0,3 0,4 0,3 0,1 0,6 0,3 0,2 0,1 0,1 0,1 0,1 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 2,79 2,76 2,76 2,96 2,77 2,64 2,65 2,75 2,61 2,71 Table 3.1 shows that the calculated energy of the carrier molecules range from 2.62 eV (compound Cz5) to 2.96 eV (compound D3b) In general, the DBTa system shows higher triplet energies than other systems Specifically, the ET1 values of the Cz, DBTa and DBTb systems range from 2.62 to 2.83, from 2.75 to 2.92, and from 2.64 to 2.96 eV, respectively The average E T value of the DBTa group (2.83 eV) is larger than that of Cz (2.75 eV) and DBTb (2.76 eV) Accordingly, most of the studied carriers have E T values greater than that of Firpic (2.71 eV), except Cz5, Cz6, D5b and D6b Therefore, these compounds are expected to act as suitable carriers for blue color with the emission material being Firpic-like compounds Interestingly, the nitrogen atom substitution at positions 3a and 3b of the DBTa and DBTb units yielded compounds D3a and D3b, giving the largest ET1 values of 2.92 and 2.96 eV, respectively The λ h and λe of the designed compounds ranged from 0.14 to 0.23 eV and from 0.12 to 0.29 eV For most compounds, except Cz7, D2a, D5a, D6a and D6b, the recombination energy values for hole transport process are slightly larger than those for electron transport This indicates that the hole transport efficiency of the studied molecules is more favorable than the hole transport efficiency In other words, the small difference between both the hole and electron reconstruction energy (0.010.11 eV) indicates that our designed carrier molecules possess the necessary characteristics to serve as potential compounds for dipole carrier molecules Compounds with an N atom replacing the CH group at positions 3a (compound D3a) and 3b (compound D3b) have higher triplet energy values than other positions 3.2 Synthesis of 2-Alkenylbenzo[1,2-b:4,5-b']dithiophene by Pd/Cu/Ag catalyst and structure study by experimental spectroscopy and theoretical calculation methods 14 Figure 3.2: Synthesis and performance diagram Table 3.2: Synthesis process parameters Experimen t Pd(II) (% mol) Cu(II) (% mol) Ag(I) (equivalent) Temperature (°C)/Time (h) 10 20 110/24 10 20 110/24 10 20 100/4 48 20 100/14 18 10 20 100/14 21 10 20 AgOAc, 0,4 AgOCOCF3, 4,0 AgOCOCF3, 4,0 AgOCOCF3, 2,0 Ag2O, 1,0 No response Efficiency (%) 100 This study presented a convenient and selective method for the direct alkenization of benzo[1,2-b:4,5-b']dithiophene under normal reaction conditions (Figure 3.2 and Table 3.2) The theoretical calculation based on the DFT method also shows the preferential position of the substituent to create the structurally stable product and the electronic properties are also calculated and consistent with the experimental parameters (Table 3.3) 15 The selectivity of the reaction can be explained by the electronphin substitution reaction at the C2 site of BDT Table 3.3: The HOMO, LUMO, Egap, EA IP energy values of the compounds studied in eV Compound BDT 3a 3b 3c 3d 3e EHOMO -5,74 -5,93 -5,91 -5,90 -5,90 -5,82 ELUMO -1,45 -2,48 -2,45 -2,44 -2,43 -2,29 Egap 4,29 3,44 3,46 3,46 3,46 3,53 EA 0,03 1,18 1,16 1,16 1,16 1,05 The Egap= ELUMO – EHOMO value shows that the energy of the orbitals in BDT are changed significantly due to the addition of substituents to the BDT framework, especially the LUMO energy The HOMO energy values of the five derivatives ranged from -5.82 eV (3e) to -5.93 eV (3a) while the LUMO energy values ranged from -2.29 eV(3e) to -2.28 eV (3a) When compared with the HOMO and LUMO energy values of BDT (-5.74 eV and -1.45 eV), the change of LUMO energy is much larger than that of HOMO, demonstrating the addition of electron-absorbing substituents is the reason for the stable energy of LUMO The change of LUMO energy reduces the Egap value from 4.26 eV in BDT to about 3.5 eV in alkene derivatives The calculation results show that the electron acceptor ability of the derivative is better than that of BDT, so it is suitable to be used as an electron acceptor in D-A or D-π-A type compounds 16 IP 7,38 7,38 7,35 7,34 7,34 7,22 3.3 Design of conjugated bithiophene system containing silole and some pentagonal heterocycles for photovoltaic materials Figure 3.3: The structures of the designed compounds The HOMO and LUMO energy levels of the designed compounds (Figure 3.3) varied between -4.6 to -5.4 eV and -1.4 to -2.5 eV The HOMO energy levels of all designed compounds are higher than that of 4.4′-bis(Ncarbazolyl)-1,1′-biphenyl (CBP, calculated value: -5.3 eV, experimental value: -5.7 eV) is a common compound and has been used as a good hole transport material (HTM) The results suggest that the designed compounds may perform better as HTM than the commonly used CBP compounds Compounds of groups b, c and f not only have a higher (more positive) HOMO energy level, but also a lower (more negative) LUMO energy level than the compounds of the other group The recombination energy for electrons and holes of some compounds include DTSPh-f (0.28-0.29 eV), CPDT-c (0.30-0.27 eV), CPDT-d (0 .29-0.26 eV), DTP-d (0.28-0.25 eV) eV), DTP-e (0.23-0.24 eV), DTP-f (0.26-0.23 eV), DTT-f (0.26-0.25 eV), 17 DTSH-f (0.27-0.28 eV) and DTSMe-f (0.27-0.28 eV) are small and roughly equal, showed that these compounds improved the balance between hole and electron transport in the molecule [136] The λ h value of these compounds is less than that of N,N'-diphenyl-N, N'-bis(3-methylphenyl)-(1,1'-biphenyl)4,4'-diamine (TPD) is a common hole-carrying material with λ h = 0.29 eV Thus, the hole transport rate of the designed compounds is expected to be higher than that of TPD, suggesting that they can be used as good HTM Compounds of group c have the highest light absorption efficiency value due to the largest fluctuation in intensity f, which can become colorants in photosensitive pigments solar cells Accordingly, the absorption efficiency of the groups can be classified as follows: c > b > f, d > g > a > e > h > The continuous electron conjugation between the bithiophene condensing group and the substituent leads to the most predominant excitations arising from the HOMO → LUMO transition, corresponding to the π → π* transition All designed molecules show good π-conjugation and most compounds with substitution at the α-carbon position of the condensed bithiophene ring confer a smaller Egap energy, at the same time better charge transport and injection properties than the parent compound for each system Among the studied systems, the compounds of group c (phenylsilolyl derivatives) not only exhibit small and balanced equilibrium of electron and hole recombination energy, but also have high LHE in all systems The phenylsilolyl derivatives (DTSH-c; DTSPh-c; DTSMe-c; DTP-c; DTT-c; CPDT-c) have the best properties, suggesting that silole derivatives emerge as effective substituents to create promising dipole charge transport materials to be used in optoelectronic applications such as OLED and DSSC 3.4 Research on the structure and photoelectric properties of some dithienosilole derivatives 18 Figure 3.4: Structures of compounds 1-11 19 The results obtained from the calculation for dithienosilole system (Figure 3.4) are as follows: - Attaching two phenyl groups at the silicon atom as well as changing the functional groups at the 1,1' position is an effective way to induce significant changes in the photoelectric properties of DTS-containing compounds - The binding of the pyridyl substituent effectively reduces the LUMO energy level and the band gap energy, thereby increasing the charge transport rate - In terms of optical properties, the UV spectrum of derivatives 1-11 often has a red shift compared to the original DTS compound Furthermore, the addition of π-conjugated substituents not only shrinks the band gap, but also improves the performance in the application of DTS dimers as emission materials - Among the compounds studied, dimers can be considered as potential compounds for use in the electron transport layer of OLED and solar cells (DSSC) 3.5 Theoretical study of the influence of π-bridges on organic system Dπ-A apply for polymer solar cells 20 Figure 3.5: Studied substance system Based on compounds with high energy conversion efficiency (Figure 3.5), D-π-A compounds are designed for application in polymer solar cells with good energy conversion efficiency The properties of the substance system are studied theoretically by the density functional method The main purpose of this research is to evaluate the influence of the π-bridge on the photoelectric properties of the materials From the results of the energy values of HOMO and LUMO presented in Table 3.4, it can be seen that the parent compound has a larger HOMO value and a smaller LUMO value than other compounds As such, the designed compounds have a smaller Egap, thus enhancing the charge transfer capacity Table 3.4: HOMO and LUMO values of the compounds (eV) Compound Phase EHOMO 21 ELUMO Egap OS1 CPDT DTS DTP DTT Gas -5,28 -2,56 2,70 Solution -5,40 -2,67 2,74 Gas -5,03 -2,56 2,47 Solution -5,11 -2,64 2,46 Gas -5,08 -2,59 2,50 Solution -5,17 -2,67 2,50 Gas -4,98 -2,49 2,49 Solution -5,08 -2,59 2,49 Gas -5,23 -2,60 2,63 Solution -5,31 -2,67 2,64 The HOMO and LUMO values of the designed compounds ranged from -5.0 eV to -5.2 eV and -2.5 eV to -2.6 eV in the gas phase In chlorobenzene, these values ranged from -5.1 eV to -5.3 eV and -2.6 eV to -2.7 eV Thus, these LUMO values are all less negative than that of the parent compound (5.3 eV in the gas phase and -5.4 eV in the solvent), which proves that these are all good hole conductors (Table 3.5) Meanwhile, the LUMO values of the compounds did not change significantly, along with the enhanced HOMO values, reducing the Egap values of the compounds Table 3.5: Ionization energy value, longitudinal and adiabatic electron affinity, electron recombination energy and holes of compounds (eV) Compound OS1 CPDT DTS DTP DTT IEv 6,21 5,93 5,97 5,89 6,12 IEa 6,11 5,82 5,86 5,79 6,01 EAv 1,73 1,8 1,82 1,75 1,84 EAa 1,85 1,92 1,94 1,85 1,96 λh 0,23 0,22 0,23 0,2 0,22 λe 0,22 0,21 0,21 0,19 0,20 Table 3.6: Absorption wavelength (nm), vibration intensity (f) and orbital transitions of compounds 22 Compoun d OS1 CPDT DTS DTP DTT λ (nm) 525 537 588 584 578 545 f Orbital transition 1,7 HOMO→LUMO (99%) 2,2 2,0 2,4 2,2 HOMO→LUMO (99%) HOMO→LUMO (99%) HOMO→LUMO (99%) HOMO→LUMO (98%) State S0→S1 OS1 Figure 3.6: The absorption spectra of the calculated compounds in chlorobenzene solvent The calculation results show that the DTS group is the most suitable for the role of π-bridge and much better than the thiophene group used in the parent compound in terms of both molecular coplanarity as well as electrical conductivity and optical properties (Table 3.6 and Figure 3.6) 23 CONCLUSION Systematically investigated and studied the properties of the HOMOLUMO energy levels; the ability to transmit electrical charges; Optical properties of fused heterocyclic systems containing sulfur and silicon with nearly 200 different compounds by density functional method (DFT) and time dependent density functional method (TD-DFT) The results of the theoretical calculation show a relatively good agreement with the experiment (mean error less than 5%), proving that the approach is completely suitable and reliable Replaced nitrogen heterogeneous into -CH groups in the original compound M0, from which 21 different compounds were obtained In which, two compounds D3a and D3b have higher triplet excitation energy than other sites, thereby demonstrating their applicability as dipole carriers in blue light emitting OLEDs Five derivatives from BDT have been synthesized with low-cost catalyst Ag2O with an efficiency of 48% The product of the reaction is proven through 1-D, 2-D magnetic resonance spectroscopy methods and quantum chemical calculations These compounds are the primary precursors for fabricating photosensitive pigments, which are used in solar cells Discovered the rules of the role and influence of electron attraction and repulsion substituents on the semiconducting and optical properties of the studied compounds In the bithiophene system, compounds with phenylsilolyl substituents have smaller and more balanced λ h, λe values than other substituents, and significantly higher LHE values Systematically studied dithienosilole derivatives, the results show that the compounds have good charge transport ability, suitable for use as a transmission material in OLED devices, especially dime form compounds Calculation results have found DTS compound of studied system with Egap value of 2.5 eV, lower than 2.7 of PBDTS-TZNT, the parent compound 24 has been previously synthesized; The λh, λe values are 0.23 and 0.21, respectively, similar to 0.23 and 0.21 of the parent compound, and the absorption spectrum also has a red shift and higher absorption intensity 25 ... thiophene is replaced by a silicon atom Siliconcontaining heterocycles generally have lower LUMO energies than other heteroatoms, thus leading to a lower HOMO-LUMO gap Therefore, siliconcontaining heterocyclic... caused by the strong interaction between the π* orbital of the butadiene component and the antibonding σ* ortibal of the bond between the silicon atom and the substituent at the silicon atom 2.2... solution containing the main product was adsorbed onto the silica gel for purification by column chromatography The column used was 20 × 50 mm with silica gel of 40-230 mesh The solvent used was a mixture