Optical and electrical properties of semi-conducting calix[5,9]arene thin films with potential applications in organic electronics

Abstract

Indium tin oxide (ITO) substrates have been functionalized by several substituted calix [n]arene (n = 5 or 9) derivatives using spin coating to fabricate organic diode devices. The effect of rim size and side substituents has been investigated by UV-visible absorption spectrophotometry. The energy band gaps of these calixarene derivative thin films have been found in the 1.166-1.450 eV range. The electrical properties of ITO/calix[n]arene/Al diodes have been studied by current-voltage measurement showing an ohmic behaviour at low voltage. The I(V) characteristics could be modelled by a space-charge-limited current (SCLC) mechanism at high applied bias voltage. The ac electrical transport of calix[5,9]arene derivatives has been studied over a wide range of bias voltage and frequency by impedance spectroscopy. The device had been accurately modelled, for a frequency between 100 Hz and 10 MHz, by a single parallel resistor and capacitor network in series with a resistance. A dielectric relaxation time in the ms range and a transport mechanism controlled by an exponential trap distribution were deduced from the fit of the experimental data. The evolution of electrical parameters with chemical structure (rim size and substituent) has been discussed. The conductivity σ (ω) evolution with frequency and bias voltage was studied for ITO/calix[n]arene/Al devices. The dc conductivity σ dc for these devices has been determined. The ac conductivity σ ac showed a variation in angular frequency as A.ω s with a critical exponent s < 1 suggesting a hopping conduction mechanism at high frequency and a microscopic picture of the relaxation and hopping processes has been proposed.

Electrical characterization of Al/PTF/PEDOT:PSS/ITO heterojunction structure

“…As can be seen from Fig. 3 poly(pentachlorophenyl methacrylate) shows two absorption peaks at about 251 and 274 nm in the UV region and these peaks are associated with a band gap (pp* electronic transition) [2,5,[12][13][14]. There are two kinds of optical transitions at crystalline and noncrystalline materials: direct band and indirect band transitions.…”

“…There are two kinds of optical transitions at crystalline and noncrystalline materials: direct band and indirect band transitions. The optical band gap of polymer was estimated by fundamental relation given by [2,4,5,12,13,[15][16][17][18][19]:…”

Langmuir–Blodgett thin film for chloroform detection

“…3 shows the UV-vis absorption spectrum of C11TEA solution in chloroform and the major absorption peak being observed at 280 nm. This is a typical UV spectra for calixarenes and calixresorcinarenes [1] although substitution can extend the absorption peak, for example azobenzene calixarenes display UV-vis spectra with strong absorption regions around 300-400 nm [19]. The inset in Fig.…”

Study of charge transport in P3HT:SiNW-based photovoltaic devices

“…The J -V characteristics, for pure P3HT To study the mechanism of charge injection in the forward bias, we have first checked the (Space Charge Limited Current) (SCLC) behavior. Nevertheless, we have not found the classical ln J = V n behavior for J -V characteristics [36][37][38][39][40][41][42], characterized by an ohmic contact for low bias, followed by a segment with n = 2 and (sometimes) a third segment with n > 2 with increasing voltage. Several publications and reports have shown for different polythiophene derivative-based sandwich structures that, in the low field domain, thermionic emission can occur [22,[43][44][45].…”