Small molecule semiconductor building blocks are a type of building blocks which use small molecule semiconductor materials to achieve specific functions. Small-molecule semiconductors are classified into inorganic small molecule semiconductors and organic small block semiconductors. Among them, the application of organic small molecule semiconductors as building blocks is more extensive.
Small molecule semiconductor building blocks are rich in types and have excellent physical and chemical properties, so they have very wide application value in the fields of optoelectronic materials, biology, and medicine.
- Optoelectronic materials: Small-molecule semiconductor building blocks are widely used in the field of optoelectronic materials. An organic field-effect transistor (OFET) is a semiconductor device that uses π-conjugated organic compounds as semiconductor materials and controls the output loop current by controlling the electric field effect of the input loop. Organic field-effect transistors have broad application prospects in portable electronic components such as displays, solar cells, flexible displays, electronic paper and radio frequency identification. In just a few decades, with the development of organic semiconductor materials and the development of device fabrication technology, the performance of organic field-effect transistors has rapidly improved, especially the field-effect performance of some n-type small molecule materials has exceeded amorphous silicon or even close polysilicon. Perylene tetraformyl diimide (PDI) and naphthalene tetraformyl diimide (NDI) and other small molecule semiconductor materials have relatively high electron affinity, planar rigid π conjugated structure, good chemical and thermal stability. Therefore, they have become the most potential building blocks for synthesizing high-performance field-effect transistors. In addition, small molecule semiconductor building blocks can also be used to make solar cells, light-emitting diodes, etc. in the field of optoelectronic materials.
Figure 1. NDI class small molecule semiconductor building block
- Medicine: As a photosensitizer, DPP-porphyrin has the advantages of high photosensitive efficiency, strong fluorescence intensity and good light stability, etc. It can be used as a photosensitizer for photodynamic therapy, thus having a great application value in biomedicine. Photodynamic therapy (PDT) is a new method for the treatment of tumors with remarkable functions. The treatment scope includes superficial bladder cancer cells, early obstructive lung cancer, Barrest esophagus, head and neck cancer, skin cancer, etc. The basis of photodynamic therapy is the light source and the core is the photosensitizer. Pyrrolopyrrole dione (DPP) molecule has good planarity and therefore has a very good electronic conjugation structure. Each pyrrolopyrrole molecule is closely bound to the surrounding molecules by van der Waals forces, hydrogen bonding, and π-π interaction forces, so it has a high melting point, low solubility, and good heat resistance. Due to its good physical and chemical properties, pyrrolopyrrole dione has become a small molecule semiconductor building block with good performance. Introducing pyrrolopyrrole dione into porphyrin can obtain DPP-porphyrin structure, which has strong two-photon absorption. The introduction of DPP increased the absorption wavelength of DPP-porphyrin to the near infrared region, and also enhanced the molar absorption in the Q band. Therefore, DPP-porphyrin can be used as a photosensitizer for photodynamic therapy.
Figure 2. DPP small molecule for photosensitizer
- Other fields: In addition to the above fields, small-molecule semiconductor building blocks also have significant application value in other fields. π-conjugated aromatic small molecules have overlapping electron clouds. This aromatic structure is the basic structure of self-assembled semiconductor micro-nanowires. Small molecular semiconductor micro/nanowires can increase the exciton migration distance and exhibit excellent optical waveguide performance. In this way, the change of the clever light signal may be amplified, showing the super clever effect. Therefore, small-molecule semiconductor micro/nanowires can produce sensors based on changes in optical signals. This sensor has high detection accuracy and can be used to detect a variety of acid and alkaline gases.
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