Layer‐by‐Layer 2D Ultrathin Conductive Cu₃(HHTP)₂ Film for High‐Performance Flexible Transparent Supercapacitors

Abstract

2D conductive metal–organic frameworks (2D c‐MOFs) naturally possess high active sites, large specific surface areas, and fast ion transport for energy‐storage devices. However, the intelligent exploration of 2D c‐MOFs for the emerging flexible transparent supercapacitors (FTSCs) with excellent photoelectric property and electrochemical activity is rarely implemented. Herein, 2D conductive ultrathin Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11‐hexahydroxytriphenylene) film is synthesized on the indium tin oxide/polyethylene terephthalate (ITO/PET) substrate for flexible transparent conductive electrodes (FTCEs) through the layer‐by‐layer assembly method. The interconnected conductive frameworks possess the cooperative superiority of low internal resistance, fast electrolyte ion diffusion, and quick electron transfer. Cu3(HHTP)2‐15/ITO/PET FTCEs show high photoelectric property of T550 nm = 82.2% and Rs = 49.1 Ω sq−1, and high areal capacitance (CA) of 1700 µF cm−2. The corresponding symmetrical FTSCs (T550 nm = 62.1%) exhibit excellent CA of 939.2 µF cm−2 at the current density of 7 µA cm−2, superior rate capability (63.9% at 150 µA cm−2), long‐term cycling stability (85% after 3000 cycles), and mechanical flexibility under different bending angles. This work provides key insights into the design and synthesis of 2D c‐MOF films for flexible transparent energy‐storage devices.

Approaches to Enhancing Electrical Conductivity of Pristine Metal–Organic Frameworks for Supercapacitor Applications

“…Recently, Zhao et al fabricated Cu 3 (HHTP) 2 transparent film on indium tin oxide/polyethylene terephthalate (ITO/PET) substrate. [134] To ensure the strong bonding between Cu 3 (HHTP) 2 and the substrate, a layer-by-layer assembly method was employed. Briefly, the ITO/PET substrate was alternatively immersed in Cu ion and HHTP linker containing ethanolic solutions for certain cycles to achieve a layer-by-layer growth of Cu 3 (HHTP) 2 .…”

Recent Progress of Electric Conductive Metal-Organic Frameworks Thin Film

“…电化学双 电层超级电容器通过电极和电解质的电荷分离产生电 容, 与之不同的是赝电容超级电容器通过可逆的氧化还 原反应储存能量. 2021 年, 赵等 [95] 利用层层自组装法在 ITO/PET 基底上获得超薄的 Cu 3 (HHTP) 2 薄膜并应用于 柔 性 透 明 导 电 电 极 (FTCEs) 和 柔 性 透 明 超 级 电 容 器 (FTSCs). Cu 3 (HHTP) 2 /ITO/PET FTCEs 具有优异的光电 特性(透光率 T 550 nm ＝82.2%, 电阻 Rs＝49.1 Ω•sq -1 )和电 化学性能(面积电容 C A ＝1700 µF•cm -2 ).…”

“…改编自文献[95] Figure 12 The electrochemical performance of symmetrical Cu 3 (HHTP) 2 FTSCs: (a) optical transmittance of Cu 3 (HHTP) 2 -15 FTCEs and symmetrical FTSCs (Inset: optical image of the bent device); (b) CV curves measured at different scan rates; (c) GCD curves measured at different current densities; (d) cycling performance measured at the current density of 70 µA•cm-2 (Inset: GCD curves at 1st and 3000th cycles); (e) capacitance retention at different bending angles (Inset: CV curves in different bent states); (f) cycling performance measured at the bending angle of 60° (Inset: GCD curves at 1st and 1800th cycles). Adapted from the literature[95]…”

Flexible Cu3(HHTP)2 MOF Membranes for Gas Sensing Application at Room Temperature

“…Other gases, such as acetone vapor and NO 2, have also been investigated for sensing, using MOF materials [ 27 , 28 ]. Cu-MOF has also been used as photocatalysts [ 29 ] and supercapacitors [ 30 ] for a wider range of applications. There have been a variety of device fabrication methods employed, such as coating MOF on electrodes, using solvated “paste” [ 31 ], drop-casting [ 24 , 25 ], solvent-free mechanical abrasion [ 25 ], and in-situ film growth [ 26 ].…”