Electrosynthesis of electrochromic polymers based on bis-(4-(N-carbazolyl)phenyl)-phenylphosphine oxide and 3,4-propylenedioxythiophene derivatives and studies of their applications in high contrast dual type electrochromic devices

Five phenylphosphine oxide-containing polymers (PBCPO (poly(bis-(4-(N-carbazolyl)phenyl)-phenylphosphine oxide)), P(BCPO-co-ProD-Me₂), P(BCPO-co-ProD-Et₂), P(BCPO-co-ProD-Bz₂), and P(BCPO-co-ProD)) are electrodeposited on indium tin oxide (ITO) coated glass slide and their electrochromic performances are characterized. The optical band gap of PBCPO is 3.14 eV. P(BCPO-co-ProD-Bz₂) attains a high transmittance change (ΔT = 55% at 740 nm) and shows multicolored electrochromism from light tan (0.0 V), grayish-green (0.4 V), greenish-gray (1.1 V) to deep gray (1.2 V). Electrochromic devices (ECDs) containing phenylphosphine oxide-based polycarbazoles and poly(3,4-ethylenedioxythiophene) (PEDOT) as active electrode layers are constructed. PBCPO/PEDOT ECD displays light gray, gray, and greenish-gray at 0.0, 0.8, and 1.9 V, respectively. P(BCPO-co-ProD-Bz₂)/PEDOT ECD displays a high optical contrast (ΔT = 42.5% at 630 nm) and P(BCPO-co-ProD)/PEDOT ECD shows a high coloration efficiency (η = 454.1 cm²•C⁻¹ at 630 nm). In addition, P(BCPO-co-ProD derivatives)/PEDOT ECDs have adequate optical memories and long-term redox cyclic stability. Background: Polycarbazoles can create considerably stable radical cations (polarons) and dications (bipolarons) when increasing potentials or doping chemicals. Moreover, carbazole and phenylphosphine oxide are donor (D) and acceptor (A) units in BCPO, respectively. The incorporation of phenylphosphine oxide in polycarbazoles gives rise to the improvement of charge balances and carrier mobilities. It is interesting to investigate the absorption spectra and multicolored electrochromisms of five phenylphosphine oxide-containing polycarbazoles and their corresponding ECDs upon undergoing a redox process. Methods: A series of phenylphosphine oxide-containing anodic polymers (PBCPO, P(BCPO-co-ProD-Me₂), P(BCPO-co-ProD-Et₂), P(BCPO-co-ProD-Bz₂), and P(BCPO-co-ProD)) are electrodeposited on ITO coated glass. The absorption spectra, color variations, response time, and long-term electrochemical stability of PBCPO/PEDOT, P(BCPO-co-ProD-Me₂)/PEDOT, P(BCPO-co-ProD-Et₂)/PEDOT, P(BCPO-co-ProD-Bz₂)/PEDOT, and P(BCPO-co-ProD)/PEDOT ECDs are investigated comprehensively. Significant findings: The as-prepared phenylphosphine oxide-containing polycarbazoles exhibit multicolored electrochromism and high transmittance change (ΔT = 55% at 740 nm), which provide new structural insights to develop new generation electrochromic electrodes.