Low Band Gap Conjugated Semiconducting Polymers

Abstract

Important parameters of an organic semiconductor material are the electronic band gap (Eg) and the position of highest occupied and lowest unoccupied bands versus vacuum. These bands are called valence and conduction band for inorganic semiconductors. For organic semiconductors the bands defining the band gap are often called highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). One advantage of semiconducting polymers is the ability to tune the band gap and the position of HOMO and LUMO levels by molecular chemical design. The organic photovoltaic solar cells need absorbers with a smaller bandgap to maximize the power conversion efficiency of these devices. There are several chemical strategies to synthesize low band gap polymers for optoelectronic applications. In this manuscript, an updated overview on the current status of these low band gap conjugated polymers will be given. The design principles of low band gap polymers, the properties of the resulting materials, and important applications and devices realized with this material class will be briefly discussed.

Solution-processable infrared photodetectors: Materials, device physics, and applications

“…Various molecular engineering strategies have been applied to tune the bandgap of OSCs. Donor-acceptor (DA) CPs comprised of alternating electron-rich (donor) and electron-poor (acceptor) building blocks are now the dominant class of high-performance materials [6,181,182]. The combination of alternating donor (push) acceptor (pull) building blocks results in hybridization of molecular orbitals, HOMO and LUMO energy levels, and strong intramolecular charge transfer transitions that arise from contributions from the respective donor and acceptor units (Fig.…”

Molecular Encapsulation of Naphthalene Diimide (NDI) Based π‐Conjugated Polymers: A Tool for Understanding Photoluminescence

“…Recently,i th as become apparent that one of the most important obstacles that must be overcome in conjugated polymer design is the suppression of non-radiative decay in narrow band gap conjugated polymers. [10] Numerous recent studies have revealed that the high non-radiative voltage loss encountered in organic photovoltaics (OPVs), which holds back their efficiency, is primarily ac onsequence of the low solid state photoluminescence quantum yields (PLQYs) of the blend materials. [11,12] Hence,i ncreasing the PLQY of narrow band gap conjugated polymers is essential for next generation OPV,aswell as being appealing for light emitting diodes and biological imaging.I ti sc ommonly assumed that the close packing of conjugated polymers results in the creation of additional non-radiative decay pathways.T herefore,t he most promising strategy to increase the solid-state PLQY of conjugated polymers is to molecularly isolate the chains either through covalent or non-covalent encapsulation.…”

Deposit and Characterization of Semiconductor Films Based on Maleiperinone and Polymeric Matrix of (Poly(3,4-Ethylenedioxythiophene) Polystyrene Sulfonate)

“…Unlike inorganic semiconductors, OSCs are not atomic solids, instead they form conjugated bonds constituted by a system of π delocalized orbitals. Therefore, important parameters of these systems are the band gap (E g ) and the position of the frontier molecular orbitals HOMO and LUMO [7]. An advantage of OSCs is the ability to precisely tune those parameters by molecular design, and small modifications of the chemical structure can lead to large changes in the electrical and optoelectronic behavior [7].…”

“…Therefore, important parameters of these systems are the band gap (E g ) and the position of the frontier molecular orbitals HOMO and LUMO [7]. An advantage of OSCs is the ability to precisely tune those parameters by molecular design, and small modifications of the chemical structure can lead to large changes in the electrical and optoelectronic behavior [7]. In the OSCs these values depend on structural factors such as their π-conjugated system, planarity, the presence of electroacceptor or electrodonor groups and the aromaticity of the rings.…”