A nanocomposite ultraviolet photodetector based on interfacial trap-controlled charge injection

Abstract

Ultraviolet photodetectors have applications in fields such as medicine, communications and defence, and are typically made from single-crystalline silicon, silicon carbide or gallium nitride p-n junction photodiodes. However, such inorganic photodetectors are unsuitable for certain applications because of their high cost and low responsivity (<0.2 A W(-1)). Solution-processed photodetectors based on organic materials and/or nanomaterials could be significantly cheaper to manufacture, but their performance so far has been limited. Here, we show that a solution-processed ultraviolet photodetector with a nanocomposite active layer composed of ZnO nanoparticles blended with semiconducting polymers can significantly outperform inorganic photodetectors. As a result of interfacial trap-controlled charge injection, the photodetector transitions from a photodiode with a rectifying Schottky contact in the dark, to a photoconductor with an ohmic contact under illumination, and therefore combines the low dark current of a photodiode and the high responsivity of a photoconductor (∼721-1,001 A W(-1)). Under a bias of <10 V, our device provides a detectivity of 3.4 × 10(15) Jones at 360 nm at room temperature, which is two to three orders of magnitude higher than that of existing inorganic semiconductor ultraviolet photodetectors.

Fabrication and characterisation of hybrid photodiodes based on PCPDTBT–ZnO active layers

“…Minimization of dark current is imperative, as this limits the minimum detectable power and also the dynamic range of the HPD, as the on/off ratio can be enhanced by reducing the dark current [15]. When compared to other HPD devices in the literature, the HPD in Figure 2 exhibits relatively low dark current [16].…”

An ultraviolet photodetector with an active layer composed of solution processed polyfluorene:Zn0.71Cd0.29S hybrid nanomaterials

“…Recently, Guo et al have shown that the electrons transferred from the polymer to the QD are trapped in the QD and under illumination those electrons shift to the LUMO energy level of the polymer and align the Fermi energy level of the active layer with that of the cathode [8]. This explanation is supported by (i) the lifetime measurements performed in this study; both in solution and film phase the AV value of ADS231BE was not effected from the increase in Zn 0.71 Cd 0.29 S concentration (Table 2) 365 nm UV illumination.…”

“…In recent years, due to the possibility to change the photo physical properties through simplified chemical synthesis and easy thin film processing, quantum dots (QD) and polymer:QD hybrids attract a lot of attention in UV-PD applications [1][2][3][4][5][6][7][8], as well as the other photonic applications, such as biological imaging and contrast agents [9,10], light-emitting devices (LEDs) [11,12] photovoltaic [13][14][15], etc. Most of the QDs used in UV-PDs are binary systems, the band gap of which are tuned by varying the diameter of the nanoparticle [1][2][3][4][5]7,8,16].…”

“…Most of the QDs used in UV-PDs are binary systems, the band gap of which are tuned by varying the diameter of the nanoparticle [1][2][3][4][5]7,8,16]. However in ternary QDs, the band gap may be tuned by the relative composition of materials used as well [6,17].…”

“…CuInSe 2 , in a hybrid UV-PD [6]. Likewise, the studies focusing on the photophysical interactions between the polymer and QD nanoparticles are also limited [7,8].…”