[60]Fullerene‐quinoxaline, benzothiadiazole and benzoselenadiazole based dyads for thermally stable polymer solar cells: anchoring of substituent on fullerene with a poly(3‐hexylthiophene) polymer chain

Abstract

[6,6]‐Phenyl‐C61‐butyric acid methyl ester (PC61BM and PC71BM) is an archetypal electron acceptor in organic photovoltaic devices. However, it nucleates and grows to form aggregates or crystallites on a length scale of tens of nanometres to micrometres under thermal aging, which often results in a significant decrease in device efficiency and stability. To overcome this thermally induced performance degradation, many methods have been reported to date such as the introduction of hydrogen, halogen bonding, thermally or photochemically crosslinkable groups onto the fullerene, and the suppression of nucleation and growth of fullerene crystallites under thermal aging has been successfully demonstrated. Even though those methods are highly useful for the suppression of aggregation, we successfully demonstrated another one simple method for the same: Introduction of bulkier groups onto the fullerene, which can act as anchoring group to suppress the aggregation. In an extension of our previous work, quinoxaline (TQT), benzothiadiazole (TBTT) and benzoselenadiazole (TBST) based bulkier groups are linked to the fullerene, denoted as TQT‐C60, TBTT‐C60 and TBST‐C60, respectively, through the 1,3‐dipolar cycloaddition of corresponding azomethine ylides with fullerene. Single junction bulk heterojunction polymer solar cells were fabricated with the configuration ITO/PEDOT:PSS/P3HT:dyad/Ca/Al. The morphological stability of the active layer was monitored by transmission electron microscopy and optical microscopy. Independent of heteroatoms, all the dyads show excellent morphological stability under thermal aging compared to the archetypal acceptor PCBM due to the anchoring of substituent groups. © 2018 Society of Chemical Industry

Progress in Stability of Organic Solar Cells

“…linked three types of bulkier qulnoxaline (TQT), benzothiadiazole (TTBT), and benzoselenadiazole (TBST) to the fullerene acceptor and designed three modified novel fullerene acceptors TQT‐C 60 , TBTT‐C 60 , and TBST‐C 60 (as shown in Figure ), respectively. [ 196 ] When paired with donor P3HT, they found that all three types of modified fullerene based devices showed excellent thermal stability which all maintained over 90% of its initial PCE after being heated at 130 °C for 5 h. They proved that those added bulkier groups could act as an anchoring group to suppress the aggregation of fullerene acceptors in the active layer during the aging. Recently, Brabec et al.…”

“…Figure 20. Chemical structure diagrams of modified novel fullerene acceptors TQT-C 60 , TBTT-C 60 , and TBST-C 60 .Reproduced with permission [196]. Copyright 2018, John Wiley and Sons.…”

Quinoxaline derivatives as attractive electron-transporting materials

“…The researchers found that TQT-C 60 demonstrated enhanced morphological stability and thermal resistance compared to the phenyl-C61butyric acid methyl ester (PCBM) acceptor when used in bulk heterojunction polymer solar cell devices with poly(3-hexylthiophene) (P3HT) as the donor material. This improvement was attributed to the anchoring effect of the bulkier groups present in TQT-C 60 , which hindered the movement and aggregation of fullerene molecules within the polymer matrix [25]. The introduction of functional groups provided a strategic means to tailor the molecular structure, resulting in improved photovoltaic properties and overall PCEs (12.12-13.3%) [29].…”