Effective adjustment of the optoelectronic properties of organic conjugated materials by synthesizing p-n diblock molecules

Abstract

Because organic conjugated materials offer several advantages relative to their inorganic counterparts, the development of organic conjugated materials has been one of the most active research areas in optoelectronic materials. For almost two decades, the search for organic conjugated materials has represented a major driving force for research concerned with controlling the band gap of extended π-conjugated molecules. In particular, among the parameters affecting the performance of organic light-emitting diodes (OLEDs), the energy levels of organic conjugated materials play an important role because they can affect the driving voltage, wavelength, efficiency, and lifetime of the final device. Balanced injection and transport of electrons and holes are therefore crucial for achieving OLEDs with high quantum efficiency. In this regard, research into adjusting the energy levels of organic conjugated materials is very meaningful for the development of OLEDs. To adjust the energy levels of the organic conjugated materials, Huang et al. have presented a new molecular design and synthesis route that yields p-n diblock conjugated copolymers and oligomers. The present review summarizes and analyzes the progress on adjusting the optoelectronic properties of organic conjugated materials that is due to synthesizing p-n diblock molecules. We discusses primarily work done by Huang et al., but also discusses work done elsewhere over the past few years. We also point out issues that require attention, and highlight hot spots that require further investigation.adjust, diblock, energy levels, organic light-emitting diodes, synthesize Citation:Jiang H J. Effective adjustment of the optoelectronic properties of organic conjugated materials by synthesizing p-n diblock molecules.

Solvation effects on the ground and excited states of p–n diblock-conjugated polymers

“…p-n Diblock-conjugated polymers, 2 designed by incorporating -deficient segment (acceptor, A) and -excessive segment (donor, D) into one backbone, have proved to be successful in rational control of both the ground and excited states of conjugated polymers with desired emitting colors, optical absorption bandgaps, 3 injection and transportation balance, and energy levels for a particular plastic optoelectronic device. 4 However, because of the apparent intramolecular charge-transfer (ICT) interactions in the p-n diblock molecular architecture (or D-A molecules), the absorptions of p-n diblock-conjugated polymers are mainly due to the local excited state according to Franck-Condon principle, while their photoluminescences (PL) are usually due to the charge-transfer (CT) states, especially in the solid state or in high polar solvents, 5 leading to red-shifted emission and large Stocks shift. This high sensitivity of optical properties of p-n diblock-conjugated polymers toward surrounding environments needs to be systematically assessed, which is important not only for optoelectronic devices 6 working in thin solid films but also for chemo-/biosensors working in various solvents.…”

“…8 For the solute of p-n diblock-conjugated polymers, the repeating units of p-type and n-type building blocks of the copolymers construct an electron donor (D)-acceptor (A) system. 4 CT is most likely to occur in their excited states upon photoexcitation. Several CT models were suggested in literature: the twisted ICT (TICT), 5 planarization opposing mechanism of TICT, and the formation of polarons.…”

Dependence of the stability of organic light-emitting diodes on driving mode

“…Hence, many research groups have devoted resources to improving it. For small molecule-based OLEDs, several factors are believed to cause instabilities in these devices, such as electrochemical or thermal instabilities in the materials [2][3][4], charge imbalance between the injected holes and electrons [4][5][6][7], and instabilities at the material interfaces [4,8]. The driving method (direct current (DC) or pulsed current (PC)) is an important factor in determining the stability and lifetime of device.…”