Abstract
A novel electrochromic device (ECD) based on an electroactive ambipolar system was constructed and designed through an absorption-complementary approach. The system consisted of electroactive polyamides (PAs) with N,N,N′,N′-tetraphenyl-p-phenylenediamine (TPPA) and tetraphenylbenzidine (TPB) units in the backbone and heptyl viologen (HV) in the supporting electrolyte. Each of the electrochromic materials (ECMs), including TPPA-PA, TPB-PA and HV, provided one of the three primary colors that merged into a black color. Because of the suitable counter electrode materials used in this study, the overall operating voltage was effectively reduced; thus, the electrochemical stability and lifetime of the ECD were greatly enhanced. Furthermore, the whole system was completely transparent in its neutral or bleaching state, and the transmittance was reduced to only 6% in the colored state in both the visible and near-infrared (NIR) regions. The ECD demonstrated a high L* change (ΔL*) of 81 and a significant transmittance change (ΔT) of 60% in the visible region. Thus, through the excellent combination of the electrochromic and ambipolar characteristics of the system, a genuine ‘highly transparent to truly black’ ECD was successfully fabricated, implying the great potential of this device as a shutter in transparent displays and related devices.
Highlights
Display technology has developed for nearly a century
Since the 1920s, the majority of display materials were based on cathode ray tubes that lasted for several decades until they were replaced by plasma liquid crystal displays and solid-state devices, such as organic lightemitting diodes[1,2] and light-emitting diodes
This excellent performance is attributed to the increased thickness of Blending-O film. Despite this electrochromic devices (ECDs) showing excellent visible light absorption at its colored state, the transmittance over the visible spectrum was reduced to only 55% in the neutral form, indicating that the transparency of the ECD was obviously sacrificed at the bleached state
Summary
Display technology has developed for nearly a century. Since the 1920s, the majority of display materials were based on cathode ray tubes that lasted for several decades until they were replaced by plasma liquid crystal displays and solid-state devices, such as organic lightemitting diodes[1,2] and light-emitting diodes. Most of the ECMs with high contrast have been reported based on conducting polymers,[14,15,16,17,18,19,20,21] with only a minor amount of studies using small molecules[22,23] or metallo-supramolecular polymers.[24] there are many research groups dedicated to this research area, so far, a ΔL* of 460 over the whole visible spectrum has not been obtained This goal is especially important for ECDs that are highly transparent and colorless in their neutral states without any applied potential. The thermal properties, solubility behaviors, molecular weights and inherent viscosities of the resulting PAs are listed in the Supplementary Information
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