RESUMEN
Dimer acceptors in organic solar cells (OSCs) offer distinct advantages, including a well-defined molecular structure and excellent batch-to-batch reproducibility. Their high glass transition temperature (Tg) aids in achieving an optimal kinetic morphology, thereby enhancing device stability. Currently, most of dimer acceptor materials are linked with conjugated units in order to obtain high power conversion efficiencies (PCEs). In this study, different from previous works on conjugation-linked dimer acceptors, a novel series of dimer acceptors are synthesized (named T1, T4, T6, and T12), each linked with different flexible alkyl linkers, and investigated their PCEs, device stability, and flexibility robustness. When blended with PM6, the T6-based device achieves a PCE of 17.09%, comparable to the fully conjugated T0-based device's PCE of 17.12%. The molecular dynamics simulations and density functional theory calculations suggested that flexible conjugation-broken linkers (FCBLs) promote intermolecular electronic couplings, thereby maintaining good electron mobilities of dimer acceptors. Notably, the T6-based device exhibits impressive long-term stability with a T80 lifetime of 1427 h, while in the T0-based device, T80 is only 350 h. The present work has thus established the relationship between the length of flexible alkyl linkers in such dimer acceptors and the performance and stability of OSCs, which is important to further designing new materials for the fabrication of efficient and stable OSCs.
RESUMEN
Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long-term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri-Y6-OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by-products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri-Y6-OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T80 ) for 1523â h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6-OD-based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs.
RESUMEN
Morphology control greatly influences the power conversion efficiency (PCE) and long-term stability of all-polymer solar cells (all-PSCs); however, it remains challenging owing to their complex crystallization behavior. Herein, a small amount of Y6 (2 wt%) is introduced as a solid additive into a PM6:PY-DT blend. Y6 remained inside the active layer and interacted with PY-DT to form a well-mixed phase. Increased molecular packing, enlarged phase separation size, and decreased trap density are observed for the Y6-processed PM6:PY-DT blend. The corresponding devices showed simultaneously improved short-circuit current and fill factor, achieving a high PCE of over 18% and excellent long-term stability, with a T80 lifetime of 1180 h and an extrapolated T70 lifetime of 9185 h at maximum power point tracking (MPP) conditions under continuous one-sun illumination. This Y6-assisted strategy is successfully applied to other all-polymer blends, demonstrating its universality for all-PSCs. This work paves a new way for the fabrication of all-PSCs with high efficiency and superior long-term stability.
