Recent Advances of Furan and Its Derivatives Based Semiconductor Materials for Organic Photovoltaics

The state-of-the-art bulk-heterojunction (BHJ)-type organic solar cells (OSCs) have exhibited power conversion efficiencies (PCEs) of exceeding 18%. Thereinto, thiophene and its fused-ring derivatives play significant roles in facilitating the development of OSCs due to their excellent semiconducting natures. Furan as thiophene analogue, is a ubiquitous motif in naturally occurring organic compounds. Driven by the advantages of furan, such as less steric hindrance, good solubility, excellent stacking, strong rigidity and fluorescence, biomass derived fractions, more and more research groups focus on the furan-based materials for using in OSCs in the past decade. To systematically understand the developments of furan-based photovoltaic materials, the relationships between the molecular structures, optoelectronic properties, and photovoltaic performances for the furan-based semiconductor materials including single furan, benzofuran, benzodifuran (BDF) (containing thienobenzofuran (TBF)), naphthodifurans (NDF), and polycyclic furan are summarized. Finally, the empirical regularities and perspectives of the development of this kind of new organic semiconductor materials are extracted.

Effect of carbon hybridization in 9H-fluorene unit on the photovoltaic properties of different fluorene-based conjugated polymers

To investigate the effect of different carbon hybridization in 9H-fluorene on the resultant polymers, a series of donor–acceptor conjugated polymers have been synthesized by copolymerizing substituted 9H-fluorenes with triazoloquinoxaline. All polymers exhibit good solution-processability and broad absorption in 350–1000 nm region with narrow optical bandgaps ranging from 1.27 eV to 1.55 eV. The results indicate that fluorene functionalization via different carbon hybridization on 9-position could be an effective strategy to fine-tune the absorption, energy levels, and photovoltaic performance of the polymers. 9-Position sp2-hybridized carbon in fluorene could enhance absorption of ultraviolet-visible and form good morphology of blending layers, through its planar rigid structure. All polymer solar cells devices exhibited moderate performance with the best power conversion efficiency of 3.02% achieved based on P2. Compared to ladder-type multifused fluorene, carbon-hybridized 9H-fluorene units can be a very useful building block for constructing narrow bandgap polymers with facile synthesis, and even interesting optoelectronic properties.

Alkylated Selenophene-Based Ladder-Type Monomers via a Facile Route for High-Performance Thin-Film Transistor Applications

We report the synthesis of two new selenophene-containing ladder-type monomers, cyclopentadiselenophene (CPDS) and indacenodiselenophene (IDSe), via a 2-fold and 4-fold Pd-catalyzed coupling with a 1,1-diborylmethane derivative. Copolymers with benzothiadiazole were prepared in high yield by Suzuki polymerization to afford materials which exhibited excellent solubility in a range of nonchlorinated solvents. The CPDS copolymer exhibited a band gap of just 1.18 eV, which is among the lowest reported for donor-acceptor polymers. Thin-film transistors were fabricated using environmentally benign, nonchlorinated solvents, with the CPDS and IDSe copolymers exhibiting hole mobility up to 0.15 and 6.4 cm² V^-1 s^-1, respectively. This high performance was achieved without the undesirable peak in mobility often observed at low gate voltages due to parasitic contact resistance.

A zigzag fused-ring building block for polymer solar cells

A zigzag fused-ring building block zTITI, as a new acceptor unit, was developed. This zigzag acceptor unit endows D–A copolymers with deep HOMO levels and outstanding V_oc up to 1.08 V.

Selenium-substituted polymers for improved photovoltaic performance

The power conversion efficiency of polymer solar cells was enhanced by selenium substitution in the sulfur position of a benzothiadiazole unit.

New low bandgap near-IR conjugated D–A copolymers for BHJ polymer solar cell applications

Two ultra low bandgap (E_g ≤ 1.2 eV) D–A copolymers, with UV to near-IR absorption, are synthesized and used as donors for polymer solar cells, obtaining PCEs of 7.27% and 6.68%.

Design and synthesis of new ultra-low band gap thiadiazoloquinoxaline-based polymers for near-infrared organic photovoltaic application

Two D–A copolymers, F1 and F2, with fluorene and thiazole units were substituted, respectively, on a thiadiazoloquinoxaline (TDQ) unit to enhance the electron-accepting strength of TDQ.

Design and photovoltaic characterization of dialkylthio benzo[1,2-b:4,5-b′]dithiophene polymers with different accepting units

Three dialkylthio benzo[1,2-b:4,5-b′]dithiophene polymers were developed with tuned bandgaps exhibiting a highest PCE value of 5.63% obtained for the polymer solar cells.

Small bandgap naphthalene diimide copolymers for efficient inorganic–organic hybrid solar cells

The energy level control of efficient inorganic–organic hybrid solar cells induced by using a copolymer was demonstrated.

Direct C–H arylation synthesis of (DD′AD′DA′)-constituted alternating polymers with low bandgaps and their photovoltaic performance

The alternating copolymers possess a planar backbone structure and high intramolecular charge transfer, and they contain a strong push–pull (D–A) system and gave a power conversion efficiency up to 2.36%.

Strengthening the acceptor properties of thiadiazoloquinoxalines via planarization

Fused aromatic ring extension strongly enhances the acceptor strength.