Growing role of organic materials in semiconductors
Organic materials are now key components in devices such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photovoltaics (OPVs), offering a flexible alternative to traditional devices made from inorganic materials. Small molecule organic semiconductors (OS) provide enhanced stability, leading to their prevalent use in various applications due to simpler purification processes and clearly defined molecular structures. The role of the solvent in manufacturing of small molecule organic electronics is multifaceted. It primarily serves to dissolve the organic molecules, creating a solution that can be evenly applied to a substrate. Therefore, the determination of solubility is vital in selecting solvents for the manufacturing of small-molecule organic electronics.
Solubility of organic semiconductors
Crystal16 measures transmissivity and controls temperature for 16 reactors (1 ml HPLC vials) at once is invaluable when studying the solubility data of organic compounds in various solvent systems.
The temperature-dependent solubilities and meta-stable zone width (MSZW) of four representative small-molecule organic compounds: 1,3-bis(9-cabazolyl)benzene (mCP), tris(8-hydroxyquinolinato)aluminium (Alq3), perylene (Pe) and triphenylamine (TPA), in seven solvents: Ethyl Acetate (EtOAc), Toluene, Chlorobenzene (CB), Chloroform (CHCl3), Tetrahydrofuran (THF), Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO), was measured by the polythermal method using the Crystal16 instrument (Example as shown in Figure 1).
Results
Figure 2 shows the high variation between the solubilities of the four compounds in various solvents at 25 °C and 50 °C. The solubility of compounds increases with the temperature in all solvents. For example, the solubility of TPA in THF increased from 500.35 mg/ml at 25 °C to 844.91 at 50 °C. The compound with the lowest overall solubility is Alq3, with a maximum solubility at RT of 23.5 mg/mL in chloroform, followed by Pe and mCP, respectively. TPA is highly soluble, relatively irrespective of the solvent used, with the highest solubility of 1128.38 mg/mL in chloroform at 50 °C and the lowest of 22.67 mg/mL in DMSO at 25 °C. The solubility of mCP decreases in various solvents in the following order: THF>DMF>CB>Toluene>EtOAc>DMF>DMSO.
Conclusion
The Crystal16 instrument enables you to quickly determine temperature-dependent solubility curves and MSZW information for any organic compound. This enables you to rapidly build up a solubility library for your compounds of interest, which is critical for developing liquid formulations for the manufacturing of organic small-molecule semiconductors.
Curious to learn more?
Read the full application note "Solubility assessment of organic semiconductors with Crystal16".