An Effective Strategy to Design a Large Bandgap Conjugated Polymer by Tuning the Molecular Backbone Curvature

Facile Synthesis of Dithienobenzothiadiazoles and D18-Cl Polymer via Na2S-Mediated Rapid Thiophene-Annulations for Organic Solar Cells

We present a novel synthetic route for the rapid construction of dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2-c][1,2,5]thiadiazoles via Na2S-promoted thiophene annulation. This method facilitated the synthesis of D18-Cl polymer, known for its efficacy as a polymer donor in bulk-heterojunction polymer solar cells. Starting from commercially available 4,7-dihalo-5,6-difluorobenzo[c][1,2,5]thiadiazole, various 4,7-dialkynylated compounds were obtained through Sonogashira reaction conditions. Subsequent Na2S-promoted thiophene annulations yielded DTBT and its derivatives in excellent yields within 10 minutes. DTBT was then utilized as a precursor for the concise synthesis of D18-Cl, benefiting from reduced synthetic steps, mild reaction conditions, decreased complexity, and high overall yields. In another route, a space group-bridged DTBT was directly constructed via Na2S-promoted thiophene annulations and converted into D18-Cl through a couple of steps. This developed protocol offers a straightforward and reliable synthetic tool, conducive to reducing complexities in the production of DTBT-based organic electronic materials, thereby advancing the potential commercialization of organic solar cells.

Synthesis, modification and application of titanium dioxide nanoparticles: a review

Titanium dioxide (TiO₂) has been heavily investigated owing to its low cost, benign nature and strong photocatalytic ability. Thus, TiO₂ has broad applications including photocatalysts, Li-ion batteries, solar cells, medical research and so on. However, the performance of TiO₂ is not satisfactory due to many factors such as the broad band gap (3.01 to 3.2 eV) and fast recombination of electron-hole pairs (10^-12 to 10^-11 s). Plenty of work has been undertaken to improve the properties, such as structural and dopant modifications, which broaden the applications of TiO₂. This review mainly discusses the aspects of TiO₂-modified nanoparticles including synthetic methods, modifications and applications.

Triphenyleno[1,2-c:7,8-c']bis([1,2,5]thiadiazole) as a V-Shaped Electron-Deficient Unit to Construct Wide-Bandgap Amorphous Polymers for Efficient Organic Solar Cells

The backbone shape of semiconducting polymers strongly affects their electronic properties and morphologies in films, yet the conventional design principle for building blocks focuses on using linear main chains to maintain high crystallinity. Here, we developed a V-shaped unit, triphenyleno[1,2-c:7,8-c']bis([1,2,5]thiadiazole) (TPTz), featuring two 1,2,5-thiadiazole rings fused to a triphenylene core with strong electron-withdrawing properties and an extended conjugation plane. We used TPTz to prepare a highly soluble copolymer, PTPTz-indacenodithiophene (IDT), which exhibited a wide bandgap of 1.94 eV and energy levels suitable for the donor polymer in organic solar cells (OSCs) in combination with non-fullerene acceptors. Despite the amorphous nature of the polymer film, single-junction OSCs with PTPTz-IDT:Y6 as the active layer achieved a power conversion efficiency of 10.4% (J_SC = 19.8 mA cm^-2; V_OC = 0.80 V; fill factor = 0.66), which is the highest value reported for a single-junction OSC with IDT-based donor polymers. This work demonstrates that TPTz is a promising electron-acceptor unit for developing functional polymers with zigzag structures.