In an article recently published in an open access journal Materials research accountsThe researchers discussed the recent development of perilendiimide-based oligomers and polymers, as well as their application to organic optoelectronics.
Research: Oligomers and polymers based on perylenediimide for organic optoelectronics. Image Credit: Cavan-Images / Shutterstock.com
As a traditional dye, perylenediimide (PDI) has several advantages, including structural diversity, adjustable optical and electrical properties, high affinity for electrons, strong light absorption, stability, and good electron transfer properties.
In organic electronics and photonics, PDI-based polymers and oligomers are promising candidates for n-type semiconductors. Polymer Solar Cell (PSC) is a promising clean and renewable energy technology with a number of benefits, including ease of preparation and lightweight, low cost, translucent and flexible design.
Fullerene derivatives such as [6,6]Methyl ester of -phenyl-C₆₁-butyric acid (PCBM) has long been the most common electron acceptor in the active layer of PSC. PCBM, on the other hand, has some drawbacks such as poor absorption, significant energy consumption and unstable morphology.
Compared to PCBM, PDI-based materials have many advantages. As a result, PDI-based polymers and oligomers are commonly used in PSC active layers as electron acceptors. In addition, LEDs (LEDs), organic field-effect transistors (OFETs), lasers, optical switches, and photodetectors use PDI-based oligomers and polymers as n-type semiconductors.
In this study, the authors presented a brief overview of recent advances in PDI-based polymers and oligomers, as well as their applications in organic electrical and photonic devices, particularly FET and solar cells. To overcome excess crystallization and PDI aggregation, and to achieve appropriate donor / acceptor (D / A) mixing and phase separation, the authors developed star-shaped PDI trimmers, linear PDI dimers with different bridges, and PDI polymers in 2007. .
Molecular design strategies have been developed to promote the plane of the spine and the lower level of unoccupied molecular orbital (LUMO) in PDI polymers, helping for strong intermolecular stacking, mobility and air stability OFET. The potential of PDI polymers with respect to two-photon absorption (2PA) and perovskite solar cells in addition to the application of PSC and OFET has been demonstrated. Topics of future research to optimize oligomers and PDI polymers were also suggested.
This study summarized advances in PDI-based oligomers and polymers, mainly from the Zhan group, and their potential applications in organic electrical and photonic devices, particularly solar cells and FETs. The logical design of stellar and linear polymers and PDI-based oligomers was considered together with the structure-property interactions. In addition, the main directions of research for the near future were proposed.
In this study, the researchers noted that early PSCs with bulk heterojunctions based on PDI acceptors had relatively low energy conversion efficiencies, despite the fact that the original PDI dyes have significant absorption, high electron affinity, and high electron mobility ( about 0.1%). Strong intermolecular stacking, severe D / A phase separation, and extensive crystal domains caused by the extremely flat shape of the parent PDI have resulted in low exciton dissociation efficiencies and low device performance.
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In addition, based on some studies, it has been observed that at 1520 nm the variable copolymer based on diethyrone-coronary diimide (DTCDI) and ethynylene-bound porphyrin (POR) (P- (DTCDI-E-POR)) has a larger cross-section of 2PA than 7809 GM / repeat. Increased electron mobility of 0.06 cm2 In-1 s-1 and the best air stability of n-channel OFET based on P (PDI-dithienothiophene) was due to the high-quality dielectric / polymer interface formed during the lamination process.
It was also determined that in organic electrical and photonic devices such as PSC and OFET, various linear PDI dimers, star-shaped PDI trimmers and PDI linear polymers were developed and used as n-type semiconductors.
The configuration of these PDI-based materials has been closely related to the stiffness and combination of their molecular bases and could have a major impact on their absorption, energy levels, intermolecular interactions, and charge transfer. It has also been observed that increased stiffness of the molecular backbone can lead to coherence of wave functions, delocalization of electrons along the highway, and greater transient dipole moment.
In addition, based on numerous studies, it has been observed that due to the increase in the plane of the molecular highways the uptake of PDI-based oligomers / polymers may be a shift to red. The increase in charge generation and BP in JSCs has benefited from stronger and wider absorption. By increasing the planarity of molecular highways, LUMO energy levels of PDI-based oligomers / polymers can be shifted up and down respectively.
Some studies have shown that controlling the location of molecular highways can alter the intermolecular interactions of PDI-based oligomers / polymers.
In conclusion, this study elucidated the optoelectronic capabilities of PDI-based materials. The researchers also stressed that pure PDI-based isomeric materials should be produced because regio-isomers have a significant effect on optoelectronic characteristics. They also concluded that PSCs require PDI acceptors with near-infrared (BIC) absorption and very high absorption coefficients because the highest photon density of the solar spectrum is in the BIC region.
The authors believe that PSC requires an improved molecular backbone plane to establish a fine balance between charge transport and donor / acceptor phase separation. It was also determined that the high mobility of n-channel OFETs depends on the plane of the molecular highways. This work also demonstrated that weak chemical bonds can be built between heteroatoms / functional groups on the PDI-based electron transport layer (ETL) and perovskites in high-performance perovskite solar cells.
The authors stressed that some significant research issues require further attention in the future to improve the optoelectronic properties of PDI-based materials.
Cheng, P., Zhao, X., Zhang, X., perilendiimide-based oligomers and polymers for organic optoelectronics. ASAP Materials Research Paper (2022). https://pubs.acs.org/doi/abs/10.1021/accountsmr.1c00191