Benzotriazole-Based Non-Fused Ring Acceptors for Efficient and Thermally Stable Organic Solar Cells

Powerful Role of Benzotriazole Polymers and Small Molecules in Organic Solar Cells

In the dynamic landscape of renewable energy technologies, organic solar cells (OSCs) have emerged as frontrunners, offering a sustainable and promising alternative for harnessing solar energy. This review article delves into the recent strides made in leveraging the potential of the benzotriazole nucleus within the context of organic solar cells. The unique electronic properties of benzotriazole, coupled with its structural adaptability, position it as a key component in the pursuit of enhancing OSC performance. As researchers delve deeper into the intricacies of this compound, a clearer understanding of its impact on light absorption, charge transport, and overall device stability emerges. The exploration of recent literature in the last three years reveals a rich landscape with innovation and discovery, showcasing the diverse approaches taken to incorporate benzotriazole into different OSC architectures. From fundamental studies elucidating its electronic interactions to applied research refining its integration strategies, the potential of benzotriazole in advancing the capabilities of organic solar cells becomes increasingly evident, and showing that, with the most important advances in the last three years, is the main goal of this article.

Azomethine-Containing Pyrrolo[3,2-b]pyrrole Copolymers for Simple and Degradable Conjugated Polymers

Conjugated polymers have received significant attention as potentially lightweight and highly tailorable alternatives to inorganic semiconductors, but their synthesis is often complex, produces toxic byproducts, and they are not typically designed to be degradable or recyclable. These drawbacks necessitate dedicated efforts to discover materials with design motifs that enable targeted and efficient degradation of conjugated polymers. In this vein, the synthetic simplicity of 1,4-dihydropyrrolo[3,2-b]pyrroles (DHPPs) is exploited to access azomethine-containing copolymers via a benign acid-catalyzed polycondensation protocol. Polymerizations involve reacting a dialdehyde-functionalized dihydropyrrolopyrrole with p-phenylenediamine as the comonomer using p-toluenesulfonic acid as a catalyst. The inherent dynamic equilibrium of the azomethine bonds subsequently enabled the degradation of the polymers in solution in the presence of acid. Degradation of the polymers is monitored via NMR, UV-vis absorbance, and fluorescence spectroscopies, and the polymers are shown to be fully degradable. Notably, while absorbance measurements reveal a continued shift to higher energies with extended exposure to acid, fluorescence measurements show a substantial increase in the fluorescence response upon degradation. Results from this study encourage the continued development of environmentally-conscious polymerizations to attain polymeric materials with useful properties while simultaneously creating polymers with structural handles for end-of-life management or/and recyclability.

Amplifying the photovoltaic properties of phenylene dithiophene core based non-fused ring by engineering the terminal acceptors modification to enhance the efficiency of organic solar cells

In this study, a series of eight non-fused rings-based semiconducting acceptors (AR1-AR8) were computationally developed by making modifications to the parent molecule (PTICO). In this study, a DFT analysis was conducted at an accurately chosen level of theory to gather a comprehensive inventory of the optoelectronic characteristics of AR1-AR8 and PTICO. The findings indicate that all recently developed molecules exhibit a bathochromic shift in their maximum UV-visible absorbance (λmax) with a smaller band gap (Eg). AR1 has demonstrated the most significant red shift in UV-visible absorbance and possesses the smallest Eg when compared to other recently developed acceptors. AR2 acceptor has shown the best results both as electron and hole-transporting materials owing to its smallest value of reorganization energy for electrons and holes. J61 donor was engaged to calculate the open-circuit voltage (VOC) and the highest VOC with maximum FF % value was observed in AR4. The investigation of charge transfer was also conducted utilizing J61 in conjunction with the AR4 acceptor. Natural transition orbitals (NTO) have also been inspected to recognize the percentage electron transport contribution (% ETC) from the ground state to the first excites state (S0 to S1). The findings of this research suggest that the modified acceptors exhibit potential for practical implementation in the development of organic solar cells that possess improved photovoltaic performance.

Tethered Small-Molecule Acceptors Simultaneously Enhance the Efficiency and Stability of Polymer Solar Cells

For polymer solar cells (PSCs), the mixture of polymer donors and small-molecule acceptors (SMAs) is fine-tuned to realize a favorable kinetically trapped morphology and thus a commercially viable device efficiency. However, the thermodynamic relaxation of the mixed domains within the blend raises concerns related to the long-term operational stability of the devices, especially in the record-holding Y-series SMAs. Here, a new class of dimeric Y6-based SMAs tethered with differential flexible spacers is reported to regulate their aggregation and relaxation behavior. In their polymer blends with PM6, it is found that they favor an improved structural order relative to that of Y6 counterpart. Most importantly, the tethered SMAs show large glass transition temperatures to suppress the thermodynamic relaxation in mixed domains. For the high-performing dimeric blend, an unprecedented open circuit voltage of 0.87 V is realized with a conversion efficiency of 17.85%, while those of regular Y6-base devices only reach 0.84 V and 16.93%, respectively. Most importantly, the dimer-based device possesses substantially reduced burn-in efficiency loss, retaining more than 80% of the initial efficiency after operating at the maximum power point under continuous illumination for 700 h. The tethering approach provides a new direction to develop PSCs with high efficiency and excellent operating stability.