Synthesis and Photovoltaic Properties of Two-Dimensional Conjugated Polythiophenes with Bi(thienylenevinylene) Side Chains

Abstract

Three two-dimensional (2-D) conjugated polythiophenes with bi(thienylenevinylene) side chains (biTV-PTs), P1, P2, and P3, were designed and synthesized for application in polymer solar cells. The absorption spectral, electrochemical, and photovoltaic properties of the biTV-PTs were investigated and compared with those of poly(3-hexylthiophene) (P3HT). The biTV-PTs show a broad absorption band from 350 to 650 nm; especially, the absorption spectrum of P3 displays a broad plateau and much stronger absorbance than that of P3HT in the wavelength range from 350 to 480 nm. Cyclic voltammograms reveal that the onset oxidation and reduction potentials of the biTV-PTs positively shifted by ca. 0.2 V in comparison with those of P3HT, indicating that the HOMO energy level of the biTV-PTs is ca. 0.2 eV lower than that of P3HT. Polymer solar cells (PSCs) were fabricated based on the blend of the polymers and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-61 (PCBM) with a weight ratio of 1:1. The open circuit voltage of the PSCs based on the biTV-PTs is ca. 0.1 V higher than that of P3HT, which is benefited from the lower HOMO levels of the biTV-PTs. The maximum power conversion efficiency (PCE) of the PSCs based on P3 reached 3.18% under AM 1.5, 100 mW/cm2, which is 38% increased in comparison with that (2.41%) of the devices based on P3HT under the same experimental conditions. The results indicate that the 2-D conjugated biTV-PTs are promising polymer photovoltaic materials.

Modified structure of two-dimensional polythiophene derivatives by incorporating electron-deficient units into terthiophene-vinylene conjugated side chains and the polymer backbone: synthesis, optoelectronic and self-assembly properties, and photovoltaic application

“…[1][2][3][4][5][6][7] Several successful strategies for the structural design of conjugated polymers, such as donor-acceptor (D-A) copolymerization, [8][9][10] two-dimensional (2-D) conjugation, [11][12][13] and side-chain engineering, [14][15][16] have been developed to enhance their lightharvesting ability, charge mobility, self-assembling, solubility, and turning their molecular energy levels to meet the requirements of organic electronic devices. 5,[17][18][19][20] Poly(thienylenevinylene)s (PTVs), which is one of polythiophene derivatives (PTs) containing alternating thiophene and vinylene units along the main-chains, have been intensively studied for their photoelectrical property and photovoltaic applications, due to their good charge transport property.…”

“…2,[21][22][23][24][25] In addition, previous literatures also have shown that polythiophene derivatives (PTs) with thienylene-vinylene conjugated side chains possess broader absorption spectra and relatively low-lying HOMO energy levels compared with their linear analogues, since the thienylene-vinylene conjugated side chains could extend the p-electron delocalization of polymer backbone. 2,[26][27][28][29][30] For example, chemically graing conjugated side chains onto polymer backbone through vinylene-linkage, such as thienylene-vinylene 31 and bi(thienylenevinylene), 11 is effective to extend the absorption range and down-shi the HOMO energy level of polythiophene. However, the steric hindrance of bulky branches frequently lowers the coplanarity of thiophene rings on the main chain, leading to weak crystallinity and low p-p* absorption intensity.…”

Synthesis and Characterization of Two-Dimensional Conjugated Polymers Incorporating Electron-Deficient Moieties for Application in Organic Photovoltaics

“…In addition, in order to enhance the short-circuit current density in PSCs, molecular designs should be conducive to enhancing the absorption ability of the conjugated polymer. As shown in Figure 1, two-dimensional (2-D) conjugation by vinylene linkage, such as thienylenevinylene [16], bi(thienylene-vinylene) [17], phenothiazine-vinylene [18], triphenylamine-vinylene [19], and terthiophene-vinylene [20], has proven to be a successful strategy to enhance lightharvesting ability, charge mobility and self-assembly, and adjust molecular energy levels to meet the requirements of PSCs [17,20,21]. Moreover, Tan and co-workers reported that a series of 2-D conjugated polymers incorporating different thienylene-vinylene derivatives with BDT building blocks, such as PTG1 [22] and PBDT-TID [23], not only attracted much interest but also demonstrated an effective strategy to extend the absorption range and down-shift the HOMO energy level.…”

Synthesis and photovoltaic properties of new small molecules with rhodanine derivative as the end-capped blocks

“…Power conversion efficiency (PCE) which is higher than 9% has been reached recently [2][3][4][5][6][7][8][9][10][11][12][13][14]. Currently, BHJ OSCs are based on two types of donor materials, conjugated polymers and small molecules [15,16].…”