Carbazole-based small molecule electron donors: Syntheses, characterization, and material properties

Abstract

Highlights•Novel D-A and A-D-A type small molecule electron donors were synthesized •Characterization by computational, electrochemical, and spectroscopic methods •A-D-A type materials were tested as active layer components in OSC devices •Relations between molecular structures and properties are studied and discussed Abstract Efficient synthetic methods for carbazole-based small molecule electron donors with donoracceptor (D-A) and A-D-A type structures were developed. In order to study the relation between chemical structures and material properties, the prepared compounds were characterized in detail using absorption spectroscopy, differential pulse voltammetry, and computational methods. In addition, symmetrical A-D-A type compounds were tested as an active layer component in bulk heterojunction based organic solar cell (OSC) devices with conventional structure. The results show that the two compound types have many similar properties. However, the extended molecular structure of A-D-A type compounds offer better film forming properties and higher molar absorption coefficients compared with the D-A type materials. Furthermore, the attachment of fluoro substituents in the A units has a positive effect on all solar cell device parameters. Moreover, the computational studies revealed that the molecular structures are twisted between the central carbazole D unit and -bridge which may result in inefficient intramolecular charge transfer and, also, relatively limited short-circuit currents in OSC devices.Recently, we reported a synthetic pathway to BT-based building blocks [27]. Since then, we have further developed the synthetic strategy and, here, we present the syntheses of two unsymmetrical D-A and two symmetrical A-D-A type small molecules. In these compounds, Cz acts as a D unit and either BT or its fluoro-substituted derivative as an A unit. Thiophene and thiazole have been used as a -bridge in between the D and A units. In order to find out how the changes in molecular structures affect the material properties, the prepared D-A and A-D-A type small molecule compounds have been characterized by spectroscopic, electrochemical, and computational methods.Moreover, the symmetrical A-D-A type compounds have been tested as electron donor materials in BHJ-based OSC devices. Experimental sectionCommercial reagents were used as received. 2-(3-Hexylthiophen-2-yl)-5-(4,4,5,5tetramethyl-1,3,2-dioxaborolan-2-yl)thiazole and compound 3b were synthesized using the previously published methods [27]. The chemical structures of new compounds were characterized by using NMR and HRMS techniques. Melting points (reported as peak values) of compounds 5a, 5b, 6a, and 6b were measured by using Mettler Toledo DSC 1 apparatus with a TSO800GC1 Gas Control system. Samples of 1.6-2.2 mg were placed in 40 L Al crucibles with pierced lids. The DSC scans were carried out from 5 o C to 300 o C at the heating rate of 20 o C min -1 under a nitrogen flow of 60 mL min -1 . Syntheses2.1.1. Synthesis of 4-bromo-5-fluoro-7-(5-hexylthiophen-2-yl...

Utilizing Furfural-Based Bifuran Diester as Monomer and Comonomer for High-Performance Bioplastics: Properties of Poly(butylene furanoate), Poly(butylene bifuranoate), and Their Copolyesters

“…Most likely, the more conjugated bifuran structures results in more effective chromophore–chromophore interactions with both furan and bifuran units of the polymer chains in the solid state that causes the red-shift of absorption. This effect is commonly observed with highly conjugated organic materials . The prepared films with thicknesses of ca.…”

“…This effect is commonly observed with highly conjugated organic materials. 48 The prepared films with thicknesses of ca. 0.15 mm were remarkably UV-opaque at 10 mol % or higher bifuran content.…”

Capturing Mobile Lithium Ions in a Molecular Hole Transporter Enhances the Thermal Stability of Perovskite Solar Cells

“…Electron donor moieties have to be chosen to adjust HOMO levels being compatible to the valence band of perovskite layer. Typical examples of electron donors are benzodithiophene, [20] dithienothiophene, [21] carbazole, [22] dithienosilole, [23] dithieno[3,2-b:2′,3′-d]pyrrole, [24,25] and triarylamine. [26] The choice of acceptor units would have an impact on the exciton dissociation and prevent the back transfer of electron to the conductance band of perovskite.…”

Syntheses of Thiophene and Thiazole-Based Building Blocks and Their Utilization in the Syntheses of A-D-A Type Organic Semiconducting Materials with Dithienosilolo Central Unit

“…Compound 2 ( Scheme 1 ) was received from 4,7-dibromo-5-fluoro-2,1,3-benzothiadiazole ( 1 ) using a selective Suzuki–Miyaura cross-coupling procedure developed by our group. 13 The method relies on an efficient Pd(OAc) 2 and Xantphos catalyst system. By contrast, the same catalyst system gave 3 only in 50% conversion in 22 h in the consequent reaction step where compound 2 was utilized as a starting material.…”

“…1 H NMR (400 MHz, CDCl 3 ) δ ppm: 0.85−0.91 (m, 6H), 1.27−1.36 (m, 10H), 1.39−1.46 (m, 2H), 1.59 (quin, J = 7.5 Hz, 2H), 1.70 (quin, J = 7.6 Hz, 2H), 2.66 (t, J = 7.7 Hz, 2H), 2.92 (t, J = 7.8 Hz, 2H), 6.92 (s, 1H), 6.96 (d, J = 5.1 Hz, 1H), 7.30 (d, J = 5.1 Hz, 1H), 7.71 (s, 1 H). 13 12). Magnesium chips (1.3 equiv, 35.3 mg, 1.45 mmol) and an iodine crystal were added in a reaction tube with a magnetic stirring bar.…”