Conjugated Polymer Nanoparticles Having Modified Band Gaps Assembled into Nano- and Micropatterned Organic Light-Emitting Diodes

Abstract

Nano-and micropatterns from the Langmuir− Blodgett (LB) assembly of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylene disodium salt nanoparticles (PPP-NPs) on glass substrates exhibited a variety of structures and tunable band gaps. Tuning the band gap of optical materials used in devices based on conjugated polymers is useful for manufacturing organic light-emitting diodes and optoelectronics. The PPP-NPs are prepared by supramolecular assembly of the polymer in methanol. A highly packed, collapsed PPP-NPs monolayer assembly is obtained when the uncompressed LB film is transferred to the surface of a glass substrate. The band gap of the PPP-NPs dispersed in methanol is reduced by 0.56 eV after monolayer assembly into 2D nanostructure with an average diameter of 28 ± 7 nm and 4.2 ± 0.5 nm height to be 2.47 eV. This large band gap decrease is attributed to the collapse of their supramolecular assembly, the interparticle energy transfer, and change of the dielectric function from methanol to air. Because of the soft nature of the PPP-NPs, compressing the LB film resulted in a hierarchical assembly of the PPP-NPs into microdisks with a few nanometers in thickness. The single microdisk has a band gap of 1.61 eV and a broad optical spectrum composed of multiple peaks due to random energy transfer between the PPP-NPs. When the LB film of the microdisks assembly is compressed, nanopillars of an average ∼200 nm diameter and ∼40 nm height are obtained, which have an intense optical signal. The band gap of the individual nanopillar is 1.6 eV.

Uniform Continuous and Segmented Nanofibers Containing a π-Conjugated Oligo(p-phenylene ethynylene) Core via “Living” Crystallization-Driven Self-Assembly: Importance of Oligo(p-phenylene ethynylene) Chain Length

“…π-Conjugated polymers, with fascinating and tunable optical, electronic, electrochemical, and mechanical properties, − have been considered as excellent building blocks to fabricate a variety of nanostructures for a broad range of applications from biomedicine , to optoelectronics. − For instance, a large number of π-conjugated-polymer-based spherical nanostructures with intrinsic optical characteristic have been used in biomedicine as drug delivery carriers and probes for diagnosis. , However, in comparison to spherical nanoparticles, nonspherical fiber-like nanostructures have exhibited longer blood circulation times, better cell uptake rate, a more efficient inflammatory response, and higher adhesion ability. − These properties are highly related to the length and composition of fiber-like nanostructure. Additionally, a large variety of π-conjugated-polymer-based nanostructures with diverse morphologies and compositions also have been prepared and utilized as key components to improve the performance of π-conjugated-polymer-based optoelectronic devices. − Among these nanostructures, nanofibers have emerged as promising active components featuring improved charge mobility, emission quantum yield, and polarized emission compared to bulk or thin film of conjugated polymers because of high chain ordering and favorable orientation of conjugated polymers within nanofibers. − For instance, Jin et al recently reported that the exciton diffusion length can exceed more than 200 nm in nanofibers with a crystalline poly­(fluorene) core, whereas values of typical organic/polymeric solar cells are only about 10 nm .…”

Modulating the Optical Band Gap of Small Semiconducting Two-Dimensional Materials by Conjugated Polymers

“…Investigating the Possibility of Electron Injection from the CP to MoS 2 . Raman spectroscopy provides a fingerprint for inorganic materials, such as MoS 2 , 47 and molecular compounds 48 such as P3HT and PCBM. The number of layers of MoS 2 and the defect density can also be estimated from the Raman spectrum.…”

Employing bulk-heterostructure conductive polymer PFO/PFBT for the photoelectrochemical analysis of p-phenylenediamine

“…21 Organic polymer semiconductors, especially polymers, with advantages of tunable band gap, broad light absorption spectra, highly optical absorption coefficient, solution processable fabrication, and good film forming properties have emerged as attractive candidates to construct bulk-heterojunction. [22][23][24] Photocurrent generation in organic bulk-heterojunction is most commonly understood as a photoinduced electron transfer (PET) process, which predominantly involves the photoexcitation of one semiconductor followed by electron transfer to the another. 25,26 The characteristic length scale of the interpenetrating network in the block is tens of nanometers, which is important for reducing charge recombination and enhancing charge separation.…”