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.

photodetector; the corresponding responsivity and normalized detectivity were 0.5 A/W and 2.3 × 10 9 Jones, respectively. [ 19 ] It is reasonable to anticipate a better detector performance if the photon-to-current conversion effi ciency can be further improved.In this manuscript, we report a PbS-based NIR hybrid photodetector with an EQE above 100% by the integration of zinc oxide (ZnO) QDs to induce a photoconductive gain. The active layer of the photodetector can be prepared by a single cycle of spin-coating. Moreover, the photodetector shows a tenfold higher responsivity than that of commercial SiC and Si photodetectors in the UV-visible range at room temperature.The structure of the dual-QD hybrid photodetector is presented in Figure 1 a. The device structure is similar to bulk heterojunction solar cells with indium tin oxide (ITO) and aluminium used as the anode and cathode, respectively. Both PbS and ZnO QDs were introduced into the polymer blends. The PbS QDs in this study were synthesized by a hot-injection technique involving the quick injection of bis(trimethylsilylsulphide) into a hot lead precursor. [21][22][23] The average diameter of PbS QDs was about 3.3 nm (maximum 3.7 nm), calculated from the absorption curve. Ligand exchange was processed in the solution phase, and the obtained butylamine-capped PbS QDs were dissolved in 1,2-dichlorobenzene (DCB).ZnO QDs were prepared by the hydrolysis method developed by Pacholski, [24][25][26] where ZnO QDs are obtained by quickly adding potassium hydroxide solution into zinc acetate methanol solution. The diameter of the ZnO QDs was approximately 5 nm and the obtained ZnO QDs were also dissolved in DCB. The synthesis method is highly reproducible and reliable, and the ZnO QD solution is almost transparent and can be kept at room temperature for more than three weeks.The polymer blend consists of hole conductor P3HT and electron conductor PCBM which has been extensively studied in an organic solar cell. [ 27,28 ] ZnO QDs and PbS QDs were mixed with a P3HT:PCBM polymer blend separately, and then mixed together right before the coating of the quartenary blend fi lms to avoid the aggregation of ZnO and PbS QDs. Solvent and post-thermal annealing were performed in order to obtain an optimized fi lm morphology for better carrier separation and transportation in a polymer matrix (see the Experimental Section for details). Optical sensing from the ultraviolet (UV) to the near infrared (NIR) range have broad applications including imaging, telecommunications, biomedicine, environmental monitoring and defence sensing. [1][2][3] It is desirable to have a photodetector with a response spectrum covering a broad spectral range from UV to NIR. However, commercially available solid-state photodetectors have relatively narrow response spectra. For example, silicon photodetectors are only good for the visible/ NIR range, while high-end photodetectors made of SiC are generally selected for UV sensing. Organic/polymer photodetectors are attractive low-cost, uncooled candidates ...

A solution-processed fullerene-based organic Schottky junction photovoltaic device is fabricated to produce a large open circuit voltage, 0.85-0.95 V, which is higher than that of most organic bulk-heterojunction devices. A power conversion efficiency of 5% is achieved in fullerene-derivative [6,6]-phenyl-C71-butyric acid methylester-based Schottky junction devices.

White organic light-emitting diodes made of two electroluminescent (EL) units connected by a charge generation layer were fabricated. Thus, with a tandem structure of indium tin oxide/N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB)/9,10-bis-(β-naphthyl)-anthrene (ADN)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(8-hydroxyquinoline) aluminum (Alq3)∕BCP:Li∕V2O5∕NPB∕Alq3:4-(dicyanomethylene)-2-t-butyle-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)4H-pyran (DCJTB)∕Alq3∕LiF∕Al, a stable white light with Commission Internationale De L’Eclairage chromaticity coordinates from (0.35, 0.32) at 18V to (0.36, 0.36) at 50V was generated. It was clearly seen that the EL spectra consist of red band at 600nm due to DCJTB, green band at 505nm due to Alq3, and blue band at 435nm due to ADN, and the current efficiency and brightness equal basically to the sum of the two EL units. As a result, the tandem devices showed white light emission with a maximum brightness of 10200cd∕m2 at a bias of 40V and a maximum current efficiency of 10.7cd∕A at a current density of 3.5mA∕cm2.