A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

Abstract

Cathodic electrochromic materials realized by n-type doping of conducting polymers are scarce. Even with limited cases reported in the literature, long-term stability is an urgent problem to be solved. Herein, we report a high performance and stable cathodic electrochromic material, poly(Th-Cl-PBI), based on a perylene bisimide function core. Due to its high electropolymerization efficiency and low steric hindrance of thiophene groups, perylene bisimide, which generally does not dissolve and form film easily, can grow to the sufficient thickness of 350 nm for wide-range spectral modulation and large-capacity energy storage. The optical contrast of optimized film with a thickness of 240 nm reaches as high as 69.1% at 520 nm, 94.1% at 760 nm, and 95.7% at 680 nm. Theoretical simulation based on the Lambert-Beer law also verifies this optical contrast dependent on film thickness. Besides, during the transition between the neutral state and radical anion state, it maintains 90.2% of the electrochemical activity after 4000 cycles, and the transmittance spectrum remains stable after 2000 cycles. The cation size effect on cathodic electrochromic process and cyclic stability has been investigated.

Enhanced Long-Term Stability of Organic Electrode Materials by a Trap Filler Strategy

“…The results (Figure S13) revealed that for BthCz and AQCz, there was no Bth or AQ anion peak even though the concentration ratio was as high as 1:50. As for PBICz, when the concentration ratios of PBICz and DMC were up to 1:30 and 1:50, two new peaks attributed to the PBI anion appeared at 761 and 922 nm, 34 and the intensity of those were higher at a ratio of 1:50 (Figure S13d inset). The results above illustrated that the electron transfer from DMC to electrode materials is closely related to their energy difference, concentration ratio, and the competition between electrode materials and water/oxygen traps.…”

Recent Advance in Electrochromic Materials and Devices for Display Applications

“…ECMs can be further classified into two categories, namely inorganic ECMs and organic ECMs. [32,33] Inorganic ECMs have been widely used since they possess better stability and mature processing techniques. Organic ECMs can achieve color changes throughout the full spectrum from UV to IR, while the color changes of inorganic ECMs typically only occur in the visible range.…”

“…ECMs can be further classified into two categories, namely inorganic ECMs and organic ECMs [32,33] . Inorganic ECMs have been widely used since they possess better stability and mature processing techniques.…”

Cyclic secondary amine functionalized perylene diimide polymers for solution processed electrochromic devices

“…22 Consequently, within the various conjugated organic polymeric and small molecule available, anodically colored materials are typically based on electron-rich polythiophenes, 23–25 polyaniline (PANI), 26–28 polypyrrole (PPy), 29–31 carbazole, 32,33 and triarylamine, 34,35 while cathodically colored materials are based on electron-deficient viologens 36–38 and rylenimide derivatives. 39–42…”

“…22 Consequently, within the various conjugated organic polymeric and small molecule available, anodically colored materials are typically based on electronrich polythiophenes, [23][24][25] polyaniline (PANI), [26][27][28] polypyrrole (PPy), [29][30][31] carbazole, 32,33 and triarylamine, 34,35 while cathodically colored materials are based on electron-deficient viologens [36][37][38] and rylenimide derivatives. [39][40][41][42] Self-assembly in organic conjugated materials can significantly influence their solubility, optical absorptivity, charge-transfer, and ion-transport properties. [43][44][45] For instance, planarization of the conjugated backbone can promote aggregation, leading to an improved absorption coefficient and charge-transfer.…”