Optoelectronic Materials

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Introduction

Optoelectronic technology has been leading the trend of technological revolution, and optoelectronic materials and devices are the basis of optoelectronic technology, which play a decisive role in the development of optoelectronic industry. Organosilicon materials are widely used in all walks of life because of its excellent performance. And with the continuous growth of quantity and variety, the application field of organosilicon has been continuously broadened. At present, organosilicon polymer materials have become a research hotspot in optoelectronic materials, among which the most widely used materials are polysilane. When the side chains of polysilane have different functional substituents or copolymerize with different functional polymers, they both can show great potential in photoelectric materials. In addition, the materials based on polysiloxane have also been applied in the field of optoelectronics.

Fig. 1. The structures of (a) polysilane and (b) polysiloxane.

Applications of polysilane

Used as nonlinear optical materials: With the rapid development of laser technology, nonlinear optical technology, which is one of the foundations of optoelectronics, has also achieved rapid development and promoted the development of nonlinear optical materials. Polysilane has become a class of classical nonlinear optical materials due to its special physical, chemical and optical properties, showing various advantages: (1) When the electrons on the its backbone transition, it is completely transparent in the visible region and even the near infrared region, which reduces the loss of light; (2) With the change of polysilane substituent, the UV absorption peak can be shifted; (3) The asymmetric polysilane can easily soluble in organic solvents, then it is easily made into a film for optical research; (4) The polysilane shows good thermal stability and chemical stability. In addition, the σ-π conjugated copolymer can be formed by copolymerization of polysilane and π-conjugated polymer, which can greatly improve optical properties of polysilane.

Used as photoresist: Photoresist is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. Photoresist is indispensable in the production of semiconductors and printed circuit boards. Photoresist can be divided into positive type and negative type according to the photosensitive mechanism. Polysilane is easily decomposed or cross-linked when exposed to light, which is exactly in line with the requirements of photoresist. When polysilane occurs photodegradation reaction, it can be made into positive photoresist. And the small molecule compounds formed by degradation are completely volatilized so as to realize pattern. When the polysilane occurs photocrosslinking reaction, negative photoresist can be made.

Fig. 2. The process of photolithography uses polysilane as photoresists ^[1].

Used as electrical conductor: Polysilane has relatively stable electrical properties, rarely affected by environmental, temperature and other factors, so, it's a potentially good conductive material. However, due to its structural characteristics, the conductivity is not outstanding. Generally, there are three methods to improve its conductivity: (1) Doping some strong electron acceptors such as SbF₅, I₂, TCNQ in the polysilane structure; (2) Introduction of conjugated side groups (such as acetylene group, naphthyl group, phenylacetylene group, etc.) or/and some functional groups; (3) Improvement of its delocalization.

Other: Polysilane can be made into a variety of light emitting diode using its unique fluorescent effect and can be used in optically controlled switches or wavelength conversion materials using the special optical effect caused by π-electron conjugation on Si-Si chain; It also can be used in electroluminescence devices through the improvement of the luminescence efficiency in the visible region by adding fluorescent molecular (such as rhodamine) into the its side-group.

Applications of polysiloxane

Since there is no delocalized σ electron on the Si-O-Si backbone, polysiloxane itself has no photoelectric properties and cannot be directly used in photoelectric materials. In practical applications, polysiloxane is mainly used as an insulator of photoelectric devices, for examples, as a coating or packaging film for high-frequency electronic instruments; as a buffer layer for fiber optic cables to isolate noise. However, due to the excellent physical and chemical properties, polysiloxane can be combined with polymers to improve its photoelectric properties. For examples, amphoteric copolymer can be synthesized by polymerization of hydrophobic polysiloxane and hydrophilic polyoxyethylene, which can make conductivity of polysiloxane greatly improved and the result material can be used as a semiconductor. Second-order nonlinear optical properties of polysiloxane can be obtained by introducing colorimetric groups into the side chains of polysiloxane.

What can we do?

Alfa Chemistry has many years of research strength in the field of organosilicon applications and is committed to promoting the further application of organosilicon in optoelectronic materials. We can provide customers with a variety of polysilane and polysiloxane for optoelectronic materials and also offer technical support and services for optoelectronic materials research. If you require any assistance, please contact us and our team will provide you with fullest support at the most abundant experience and the most affordable price.

Reference

Kumar V. B. and Leitao E. M. Properties and applications of polysilanes[J]. Applied Organometallic Chemistry, 2020, 34(3): e5402.