Photorefractive performance of polymer composite sensitized by CdSe nanoparticles passivated by 1-hexadecylamine

Abstract

The performance of a photorefractive polymer composite sensitized by 1-hexadecylamine capped CdSe nanoparticles is reported. The polymer composite also comprises the charge transporting matrix poly(N-vinylcarbazole) and the electro-optic chromophore 1-(2-ethylhexyloxy)-2,5-dimethyl-4-(4-nitrophenylazo) benzene. At an applied field of 70 V mm À1 two beam coupling gain of 13.2 cm À1 was observed, confirming the photorefractive nature of the induced grating. At the same field, a holographic contrast of 9:12 Â 10 À4 AE 6 Â 10 À6 , a photorefractive sensitivity of 5:1 Â 10 À4 AE 0:2 Â 10 À4 cm 3 J À1 and a space-charge field rise time of 13 AE 1 s were obtained.

Organic Photorefractive Materials and Applications

“…However, a relatively thin shell of the small molecule 4-methylbenzenethiol was ascribed to present only a thin barrier to charge transfer between host and QD, which resulted in astonishing fast PR-response [ 133 ] (see Table 3 ). Contrarily, the direct comparison of 1-hexadecylamine (HDA) capped CdSe QD [ 134 ] yielded two orders of magnitude higher sensitivity compared to tris-n -octylphosphine oxide (TOPO)-capped CdSe particles, [ 141 ] the former molecule forming the thicker capping. Photoluminescence studies on both particles exhibited bathochromic shifted spectral features regarding the excitonic peak for TOPO capped CdSe QD only, which indicates the presence of detrimental charge traps on the dot surface.…”

Shape dependent properties of CdSe nanostructures

“…Charge generation efficiency can be controlled by modifying the nanoparticle surface, either by using a different synthesis route [14] or by modifying the nanoparticle surface by growing a shell of a higher band gap material around a central core or by attaching ligands to the surface [15]; these ligands reduce the number of dangling bonds, hence reducing the number of surface traps. Charge carriers caught in one of these traps increase the potential barrier for charge transfer to the surrounding matrix and thereby reduce the photogeneration efficiency.…”

Type-II core/shell nanoparticle induced photorefractivity

“…[8][9][10][11][12][13] So far the reported photorefractive performances of almost all QD-polymer composites have been low with response times of several seconds and diffraction efficiencies less than one percent at modest biases. 8,[14][15][16] Limited success has been reported by growing a wide band gap shell material on the surface of core QDs. While these type-I core/shell QDs led to an enhanced refractive-index modulation, it came at the cost of slow response times.…”