"All-organic" electrode materials toward high-performing rigid to flexible supercapacitor devices

Donor-acceptor pi-conjugated organic materials have emerged as intriguing electrode materials for reversible energy storage applications owing to their excellent charge transfer ability, high electrical dipole moment, and good electrical conductivity. Such redox behavior can be utilized in designing and fabricating hybrid supercapacitor devices. We herein fabricate low-cost, rigid to flexible, and symmetrical supercapacitors (SSCs) using perylene diimide-2-amino benzimidazole (PDI-AB, 1) with a device configuration of (ITO/PDI-AB//PMMA-LiClO4-PC//PDI-AB/ITO), where poly(methyl methacrylate)-based PC-LiClO4 gel is used as the electrolyte-cum separator. The as-fabricated PDI-AB-based rigid supercapacitors exhibit a specific capacitance (CS) of 33.87 +/- 0.66 mF g-1 at a 0.5 mA g-1 current density with a significant energy density of 12.04 +/- 0.23 mW h kg-1 at a power density of 1.6 +/- 0.03 W kg-1. The devices show nearly 93.9% retention of CS even after 2000 cycles, indicating the excellent cyclic stability and robustness of the devices. Similarly, the flexible SCs show a CS of 32.68 +/- 0.44 mF g-1 with energy density and power density values of 11.62 +/- 0.15 mW h kg-1 and 1.6 +/- 0.02 W kg-1, respectively. PDI-AB exhibits a lower bandgap of 2.45 eV in comparison to pristine PDI (2.99 eV) resulting in enhanced redox behavior owing to the extended pi-conjugation. The same devices were tested for photocurrent generation, showing a responsivity of 0.8 mu A W-1 under white light illumination (439 mW cm-2). The current study will offer new avenues toward 'all-organic' active electrode materials for flexible, compact, lightweight, 'on-chip' supercapacitors and optoelectronic devices. Perylene diimide-2-amino benzimidazole, a donor-acceptor pi-conjugated organic molecule, is utilized in fabricating rigid to flexible hybrid symmetric supercapacitor devices which exhibit nearly 96% retention of capacitance even after 2000 cycles.