Doping Molar Research Articles

White-Emissive Self-Assembled Organic Microcrystals.

Organic semiconductor micro-/nanocrystals with regular shapes have been demonstrated for many applications, such as organic field-effect transistors, organic waveguide devices, organic solid-state lasers, and therefore are inherently ideal building blocks for the key circuits in the next generation of miniaturized optoelectronics. In the study, blue-emissive organic molecules of 1,4-bis(2-methylstyryl)benzene (o-MSB) can assemble into rectangular microcrystals at a large scale via the room-temperature solution-exchange method. Because of the Förster resonance energy transfer, the energy of the absorbed photons by the host matrix organic molecules of o-MSB can directly transfer to the dopant organic molecules of tetracene or 1,2:8,9-dibenzopentacene (DBP), which then emit visible photons in different colors from blue to green, and to yellow. More impressively, by modulating the doping molar ratios of DBP to o-MSB, bright white-emissive organic microcrystals with well-preserved rectangular morphology can be successfully achieved with a low doping ratio of 1.5%. These self-assembled organic semiconductor microcrystals with multicolor emissions can be the white-light sources for the integrated optical circuits at micro-/nanoscale.

Enhanced peroxidase activity and tumour tissue visualization by cobalt-doped magnetoferritin nanoparticles

Magnetoferritin (M-HFn) is a biomimetic magnetic nanoparticle with a human heavy-chain ferritin (HFn) shell, trapping a magnetite (Fe3O4) core that has inherited peroxidase-like activity. In this study, cobalt-doped M-HFn nanoparticles (M-HFn-CoxFe3–xO4) with different amounts of cobalt were successfully synthesized. Experimental results indicate that the controlled doping of a certain amount of cobalt into the magnetite cores of M-HFn nanoparticles enhances its peroxidase-like catalytic activity and efficacy for visualizing tumour tissues. For example, compared with sample Co0 (without cobalt doping), the peroxidase-like activity of the cobalt-doped nanoparticle sample Co60 (with a cobalt doping molar percentage of ∼34.2%) increases 1.7 times, and has the maximal reaction velocity (Vmax) values. Moreover, after a one-step incubation with Co60 nanoparticles, and using the peroxidase substrate 3,3′-diaminobenzidine tetrahydrochloride (DAB) for colour development, the tumour tissues of breast, colorectal, stomach and pancreas tumours showed a deeper brown colour with clear boundaries between the healthy and tumourous cells. Therefore, this suggests that the cobalt-doped magnetoferritin nanoparticles enhance peroxidase activity and tumour tissue visualization.

Development of metallic element-stabilized Li4SiO4 sorbents for cyclic CO2 capture

Lithium orthosilicate (Li4SiO4) doped with different metallic elements, K, Mg, Cr, or Ce, was prepared by a sol–gel method for high-temperature CO2 capture. The doped sorbents were systematically studied and compared with non-doped Li4SiO4. The influence of element doping on the crystal, textural and microscopic structure of Li4SiO4 was characterized using X-ray diffraction (XRD), nitrogen adsorption and scanning electron microscopy (SEM). The CO2 absorption properties were assessed by thermogravimetric analysis, and the cyclic absorption–desorption properties were analyzed on a fixed-bed reactor. All the metallic elements could insert into the crystal lattice. In particular, Ce doping effectively inhibited the growth of crystal aggregation, resulting in a foam-like morphology with small particle size. Thus, significantly improved CO2 chemisorption properties were achieved with higher capacity and faster absorption kinetics. The optimal doping molar content of Ce/Li4SiO4 was 0.02, with a maximum absorption capacity of 34.57 wt%. Moreover, this improved performance was maintained for 10 sorption/desorption cycles.

Fabrication of novel Ba4Y3F17:Er3+ nanofibers with upconversion fluorescence via combination of electrospinning with fluorination

PVP/[Ba(CH3COO)2 + Y(NO3)3 + Er(NO3)3] composite nanofibers were prepared via electrospinning, and then mixed oxide nanofibers were obtained by calcining the composite nanofibers in air, and finally Ba4Y3F17:Er3+ nanofibers were successfully synthesized by fluorination of the as-prepared mixed oxide nanofibers used as precursor via a double-crucible method applying NH4HF2 as fluorinating agent. X-ray diffraction (XRD) analysis reveals that Ba4Y3F17:Er3+ nanofibers are pure rhombohedral phase. The diameter of Ba4Y3F17:Er3+ nanofibers is 84.3 ± 4.9 nm under the 95 % confidence level. Upconversion emission spectra analysis manifests that Ba4Y3F17:Er3+ nanofibers emit strong green and weak red upconversion emissions centering at 523 (2H11/2 → 4I15/2), 541 (4S3/2 → 4I15/2) and 652 (4F9/2 → 4I15/2) nm, respectively, and the emitting colors of Ba4Y3F17:Er3+ nanofibers are located in the green region in CIE chromaticity coordinates diagram. The optimum doping molar concentration of Er3+ ions is found to be 9 %. Moreover, the formation mechanism and upconversion luminescence of the Ba4Y3F17:Er3+ nanofibers are also investigated. This novel preparation technique can be applied to prepare other rare earth fluoride one-dimensional nanomaterials.

A new scheme to acquire BaY2F8:Er3+ nanofibers with upconversion luminescence

PVP/[Ba(CH3COO)2 + Y(NO3)3 + Er(NO3)3] composite nanofibers were prepared via electrospinning, and then the mixed oxide nanofibers were obtained by calcination of the above composite nanofibers. BaY2F8:Er3+ nanofibers were successfully fabricated via a double-crucible fluorination method by using the prepared mixed oxide nanofibers as precursor. X-ray diffraction analysis reveals that BaY2F8:Er3+ nanofibers are pure monoclinic phase with space group of C2/m. The diameter of BaY2F8:Er3+ nanofibers is 159.9 ± 15.9 nm under the 95 % confidence level. Upconversion fluorescent spectroscopy analysis manifests that BaY2F8:Er3+ nanofibers emit strong green and weak red upconversion emissions centering at 523 (2H11/2 → 4I15/2), 540 (4S3/2 → 4I15/2) and 652 (4F9/2 → 4I15/2) nm, respectively, and the emitting colors of BaY2F8:Er3+ nanofibers are located in the green region in CIE chromaticity coordinates diagram. The optimum doping molar concentration of Er3+ ions in the BaY2F8:Er3+ nanofibers is found to be 5 %. The formation process and upconversion luminescence mechanism of the BaY2F8:Er3+ nanofibers are also studied. This novel preparative technique can be applied to fabricate other rare earth fluoride one-dimensional nanomaterials.

Er3+ doped BaYF5 nanofibers: facile construction technique, structure and upconversion luminescence

Er3+ doped BaYF5 nanofibers have been successfully fabricated by electrospinning combined with a double-crucible fluorination method we recently proposed. For the fabrication process, the first step is to prepare PVP/[Ba(CH3COO)2 + Y(NO3)3 + Er(NO3)3] composite nanofibers via electrospinning, the next step is calcining the composite nanofibers into mixed oxide nanofibers in air, and finally BaYF5:Er3+ nanofibers are successfully synthesized by fluorination of the as-prepared mixed oxide nanofibers used as precursor via a double-crucible method applying NH4HF2 as fluorinating agent. X-ray diffractometry analysis reveals that BaYF5:Er3+ nanofibers are pure tetragonal phase with space group of P/421m. The diameter of BaYF5:Er3+ nanofibers is 109.9 ± 10.9 nm under the 95 % confidence level. Upconversion emission spectra analysis manifests that BaYF5:Er3+ nanofibers emit strong green and weak red upconversion emissions centering at 522 (2H11/2 → 4I15/2), 540 (4S3/2 → 4I15/2) and 651 (4F9/2 → 4I15/2) nm, respectively. Moreover, the emitting colors of BaYF5:Er3+ nanofibers are located in the green region in CIE chromaticity coordinates diagram. The optimum doping molar concentration of Er3+ ions is found to be 5 %. The formation mechanism of the BaYF5:Er3+ nanofibers is also studied. This preparation technique can be applied to fabricate other rare earth fluoride nanofibers.

The preparation of GaN:Er3+ nanoparticles and the optical performance analysis

GaN:Er3+ nanoparticles are synthesized by ammonification of a mixture of Ga2O3 and Er2O3 in three steps. The XRD result shows that three groups of samples predominantly presents hexagonal phase of GaN and its average grain size is 25.9nm. SEM images show that the sizes of the particles are almost uniform. The sizes of the particles is 20–50nm. The optic characteristics of the samples is tested in 380nm photoluminescence(PL). From PL spectra, three characteristic peaks of Er3+ions are clearly observed in visible light region (375–650nm), this prove the GaN:Er3+ nanoparticles possess good optical properties. Simultaneously, analyze the three samples in the 520nm excitation spectrum. Among them, the sample of the doping molar concentration 6.25% achieved the most excellent optical properties.

Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution

BackgroundUn-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol–gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV–visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated.ResultsThe results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10-2 min−1.ConclusionsThe high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.Electronic supplementary materialThe online version of this article (doi:10.1186/s40201-016-0242-2) contains supplementary material, which is available to authorized users.

Ba-doping effects on structural, magnetic and vibrational properties of disordered La2NiMnO6

Barium-doped La2NiMnO6 double perovskites have been investigated in order to elucidate the role of the B-site doping on its magnetic, dielectric and vibrational properties. In all cases, we have obtained a non-linear dependence with the Barium content signaling that a 5% molar doping renders the maximum B-site ordering. By analyzing a series of gradually doped samples, we have found that the effective magnetic moment in the B-site can be enhanced by a factor of nearly 100% by 5% Ba doping. In order to exclude oxidation state induce changes, XPS and XANES measurements have been carried out concluding that nickel or manganese oxidation states ratio are not modified by the Ba doping. Raman spectroscopy correlates Ba doping with vacancies thus attributing to the latter the role of primary source for structural defects in Ba–La2NiMnO6 samples. This manuscript summarizes key consequences of the B-site ordering which are crucial to address the optimization of the magneto-electric coupling in Ba–La2NiMnO6 double perovskites.

Facile synthesis of Ca0.68Si9Al3(ON)16:Eu2+ microbelts mat with the enhanced fluorescence and mechanical performance

Yellow-emitting phosphor mat consisting of Ca0.68Si9Al3(ON)16:Eu2+ microbelts was prepared by electrospinning and subsequent nitridation. The as-prepared fiber precursor is smooth and uniform with diameter of 800 to 900nm. After removing organic templates and nitridation, the morphology of the fiber is well retained and thus a smooth microbelts phosphor mat was obtained. X-ray diffraction and the photoluminescence (PL) spectra reveals that a relatively pure Ca0.68Si9Al3(ON)16 phase and the highest spectral intensity could be obtained at a relatively low temperature of 1500°C and Eu2+ doping molar concentration of 0.1. The excitation spectra exhibits a broad band, ranging from 300 to 550nm, which could be excited by blue LED chip at room temperature. The emission spectra of all exhibits a single broad band in the 400 to 700nm region, with the maximum intensity always being at 580nm. The Ca0.68Si9Al3(ON)16:Eu2+ microbelts phosphor mat has the bending strength about 4.5MPa with a photoluminescence quantum yield as high as 65%. By employing it as yellow phosphor, a high-performance warm white LED could be fabricated with low correlated color temperature (2985K), high-color-rendering index (Ra=86) and luminous efficacy of 129.5lmW−1. Different color temperatures also could be tuned by employing microbelts phosphor mats with different thicknesses.

Synthesis and Luminescence Properties of Terbium-Doped Lanthanum Oxychloride Nanostructures.

LaOCl:Tb3+ nanofibers, nanotubes and nanobelts were prepared via electrospinning combined with a double-crucible chlorination technique using NH4Cl powders as chlorinating agent. Different morphologies of LaOCl:Tb3+ nanostructures were obtained through adjusting some of the electrospun parameters. The as-prepared LaOCl:Tb3+ nanostructures are tetragonal in structure with space group of P4/nmm. The diameters of LaOCl:Tb3+ nanofibers, nanotubes and the width of LaOCl:Tb3+ nanobelts are respectively 133.99 ± 16.95 nm, 140.57 ± 17.82 nm and 5.32 ± 0.63 μm under the 95% confidence level. Under the excitation of 230-nm ultraviolet light, the LaOCl:Tb3+ nanostructures emit the predominant emission peaks at 544 nm originated from the energy levels transition of 5D4 --> 7F5 of Tb3+ ions. The optimum molar percentage of Tb3+ in the LaOCl:Tb3+ nanofibers is 7%. LaOCl:Tb3+ nanobelts exhibit the strongest PL intensity of the three nanostructures under the same doping molar concentration. The possible formation mechanisms of LaOCl:Tb3+ nanostructures are also proposed.

Electrospinning Preparation and Photoluminescence Properties of Y3Al5O12:Eu3+ Nanobelts

Novel structures of Y3Al5O12: Eu3+ (denoted as YAG: Eu3+ for short) nanobelts were fabricated by calcination of the electrospun PVP/[Y(NO3)3+Eu(NO3)3+Al(NO3)3] composite nanobelts. X-ray powder diffraction (XRD) analysis showed that YAG: Eu3+ nanobelts were cubic in structure with space group Ia3d. Fourier transform infrared spectroscopy (FTIR) analysis manifested that pure YAG: Eu3+ nanobelts were formed at 900 °C. Scanning electron microscope (SEM) analysis indicated that the YAG: Eu3+ nanobelts have coarse surface. The width and thickness of YAG: Eu3+ nanobelts were ca. 3.25 µm and ca. 220 nm, respectively. Fluorescence spectra analysis revealed that YAG: Eu3+ nanobelts emitted the main strong emission centering at 592 nm under the ultraviolet excitation of 235 nm, which was attributed to 5D0→7F1 of Eu3+, and the optimum doping molar concentration of Eu3+ ions was 5%. CIE analysis demonstrated that the emitting colors of YAG: Eu3+ nanobelts could be tuned by adjusting doping concentration of Eu3+. The possible formation mechanism of YAG: Eu3+ nanobelts was also proposed.

Doped Organic Semiconductors: Trap‐Filling, Impurity Saturation, and Reserve Regimes

A typical human being carries billions of silicon‐based field‐effect transistors in his/her pockets. What makes these transistors work is Fermi level control, both by doping and field effect. Organic semiconductors are the core of a novel flexible electronics age, but the key effect of doping is still little understood. Here, precise handling is demonstrated for molar doping ratios as low as 10−5 in p‐ and n‐doped organic thin‐films by vacuum co‐sublimation, allowing comprehensive studying of the Fermi level control over the whole electronic gap of an organic semiconductor. In particular, dopant saturation and reserve regimes are observed for the first time in organic semiconductors. These results will allow for completely new design rules of organic transistors with improved long term stability and precise parameter control.

Quantum dot based photocatalytic decolorization as an efficient and green strategy for the removal of anionic dye

In this study, zinc sulfide (ZnS) quantum dots (QDs), as a pure and iron doped were synthesized using a chemical precipitation method in aqueous solution, in the presence of 2-hydroxyethanthiol as a capping agent. Optical and structural properties of the pure and Fe3+ ion doped (i.e. Zn(1−x)FexS) QDs were investigated by various techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–vis absorption spectroscopy. In addition, the prepared ZnS QDs, as pure and doped with various mole fractions of Fe3+ ion were used for photodecolorization of thymol blue (TB) as an anionic and pollutant dye, under UV light irradiation. In photodecolorization studies, the effect of main experimental parameters on the decolorization efficiency (DE) of QDs as green nano-semiconductors were studied and optimized. The results indicated that DE is affected by some parameters such as dopant mole fraction; the pH of initial dye solution, nanophotocatalyst amount, irradiation time, and initial dye concentration. The maximum decolorization efficiency of 100% and 99.88% was obtained at pH 9.5 of dye solution for 10ppm of TB dye, in the presence of 10mg of undoped and doped (for 5% of Fe3+) ZnS QDs, respectively.

Electrospinning preparation and photoluminescence properties of Y3Al5O12:Tb3+ nanostructures.

Novel nanostructures of Y3Al5O12:Tb(3+) (denoted as YAG:Tb(3+) for short) nanobelts and nanofibers were fabricated by calcination of the respective electrospun PVP/[Y(NO3)3 + Tb(NO3)3 + Al(NO3)3] composite nanobelts and nanofibers. YAG:Tb(3+) nanostructures are cubic in structure with a space group of Ia 3d. The thickness and width of the YAG:7%Tb(3+) nanobelts are respectively ca. 125 nm and 5.9 ± 0.3 m, and the diameter of YAG:7%Tb(3+) nanofibers is 166.0 ± 20 nm (95% confidence level). The YAG:Tb(3+) nanostructures emit predominantly at 544 nm from the energy levels transition of (5) D4 → (7) F5 of Tb(3+) ions under the excitation of 274-nm ultraviolet light. It was found that the optimum doping molar concentration of Tb(3+) ions for YAG:Tb(3+) nanostructures was 7%. Compared with YAG:7%Tb(3+) nanofibers, YAG:7%Tb(3+) nanobelts exhibit a stronger photoluminescence (PL) intensity under the same doping concentration. Commission International de l'Eclairage (CIE) analysis demonstrates that the emitting colors of YAG:Tb(3+) nanostructures are located in the green region and color-tuned luminescence can be obtained by changing the doping concentration of Tb(3+) and morphologies of the nanostructures, which could be applied in the field of optical telecommunication and optoelectronic devices. The possible formation mechanisms of YAG:Tb(3+) nanobelts and nanofibers are also proposed.

A novel strategy to synthesize Gd2O2S:Eu3+ luminescent nanobelts via inheriting the morphology of precursor

Gd2O3:Eu3+ nanobelts were fabricated by calcination of the electrospun PVP/[Gd(NO3)3 + Eu(NO3)3] composite nanobelts. For the first time, Gd2O2S:Eu3+ nanobelts were successfully prepared via inheriting the morphology and sulfurization of the as-prepared Gd2O3:Eu3+ nanobelts precursor using sulfur powders as sulfur source by a double-crucible method we newly proposed. X-ray diffraction analysis indicated that Gd2O2S:Eu3+ nanobelts were pure hexagonal in structure with space group P\( \bar{3} \)m1. Scanning electron microscope analysis results showed that the width and thickness of the Gd2O2S:Eu3+ nanobelts were ca. 2.1 μm and 129 nm, respectively. Under the excitation of 330-nm ultraviolet light, Gd2O2S:Eu3+ nanobelts emitted red emissions of predominant peaks at 628 and 618 nm which were attributed to the 5D0 → 7F2 energy levels transitions of the Eu3+ ions. It was found that the optimum doping molar concentration of Eu3+ ions in Gd2O2S:Eu3+ nanobelts was 5 %. Possible formation and sulfurization mechanisms of Gd2O2S:Eu3+ nanobelts were also proposed. This new sulfurization technique is of great importance, not only can inherit the morphology of rare earth oxides, but also can fabricate pure-phase rare earth oxysulfides at low temperature compared with conventional sulfurization method.

Controlled Synthesis and Near-Infrared Luminescence of LaOBr:Nd<SUP>3+</SUP> Nanofibers and Nanobelts

LaOBr:Nd(3+) nanofibers and nanobelts were synthesized for the first time via calcinating the electrospun PVP/[La(NO3)3 + Nd(NO3)3 + NH4Br] composites. X-ray diffraction (XRD) analysis revealed that LaOBr:Nd(3+) nanofibers and nanobelts are tetragonal in structure with the space group of P4/nmm. The morphologies and sizes of LaOBr:Nd(3+) nanostructures were investigated by scanning electron microscope (SEM). The mean diameter of the LaOBr:Nd(3+) nanofibers is 192.41 ± 18.97 nm. The width and thickness of the LaOBr:Nd(3+) nanobelts are 5.50 ± 0.48 μm and 112 nm, respectively. Under the excitation of 532-nm laser, LaOBr:Nd(3+) nanostructures exhibit the characteristic emissions of predominant peaks at 922, 1072 and 1345 nm, attributed to (4)F3/2 --> (4)I9/2, (4)F3/2 --> (4)I11/2 and (4)F3/2 --> (4)I13/2 energy levels transitions of Nd(3+) ions, respectively. The optimum doping molar concentration of the Nd(3+) ions in the LaOBr:Nd(3+) nanofibers is 1.0%. Interestingly, we found that the luminescence intensity of nanobelts is obviously greater than that of the nanofibers for LaOBr:Nd(3+) under the same measuring conditions. The formation mechanisms of LaOBr:Nd(3+) nanofibers and nanobelts were also proposed.

Study on terbium doped lanthanum oxybromide luminescent nanoribbons and nanofibers

Terbium doped lanthanum oxybromide (LaOBr:Tb3+) nanoribbons and nanofibers were successfully synthesized by double-crucible bromination of the electrospinning-derived La2O3:Tb3+ nanoribbons and nanofibers using NH4Br powders as the bromine source. The structure and morphology of the samples were investigated by X-ray diffractometry and scanning electron microscopy. The results indicated that LaOBr:Tb3+ nanoribbons and nanofibers were pure tetragonal in structure with space group of P4/nmm. The width of LaOBr:Tb3+ nanoribbons were 2.33 ± 0.33 μm and the diameter of LaOBr:Tb3+ nanofibers was 90.08 ± 15.19 nm. The photoluminescent properties of LaOBr:Tb3+ nanoribbons and nanofibers were also characterized systematically. Under the excitation of 253-nm ultraviolet light, LaOBr:Tb3+ nanostructures exhibit the green emission of predominant peak at 543 nm. The optimum doping molar concentration of Tb3+ ions in the LaOBr:Tb3+ nanoribbons is 5 %. Interestingly, the luminescence intensity of LaOBr:5 %Tb3+ nanofibers is obviously greater than that of LaOBr:5 %Tb3+ nanoribbons under the same measuring conditions. Moreover, the luminescence colors of LaOBr:Tb3+ nanostructures are located in the green region in Commission Internationale de L’Eclairage chromaticity coordinates diagram. The mechanism of double-crucible bromination method was also proposed. This new bromination technique not only can inherit the morphology of rare earth oxides precursor, but also can be used to fabricate pure-phase rare earth oxybromide at low temperature compared with conventional high temperature solid state bromination reaction method. LaOBr:Tb3+ nanostructures are promising nanomaterials for applications in the fields of light display systems and optoelectronic devices.

Preparation and Luminescence Properties of ZnO–SiO<sub>2</sub>–B<sub>2</sub>O<sub>3</sub>–Na<sub>2</sub>O:Sm<sup>3+</sup> Glass

The 40ZnO-30SiO2-20B2O3-10Na2O:Sm3+ glass was prepared by high-temperature melting method. The structure and composition of the glass matrix was investigated by Infrared spectrum (IR). The absorption, excitation and emission spectra of the samples were tested, and the results showed that the glass can emit orange shade under light excitation. The emission peaks at 565nm, 604nm and 650nm wavelength were corresponding to the 4G5/26H5/2, 4G5/26H7/2 and 4G5/26H9/2 transition emission of Sm3+, while the 4G5/26H7/2 transition emission was the strongest. So the best Sm3+-doping molar concentration was 0.4%. The spectroscopic properties indicated that 40ZnO-30SiO2-20B2O3-10Na2O: Sm3+ was expected to become a new conversion material.

Quantification of deep hole-trap filling by molecular p-doping: Dependence on the host material purity

The p-doping effect of the fluorinated fullerene C60 F36 doped into organic thin films of N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD) of different purification grades is systematically investigated by photoemission spectroscopy. By reducing the molar doping ratio to MR=2.9×10−4, the Fermi-level shift upon doping is resolved in particular at very low doping concentrations. In comparison to four times sublimated MeO-TPD, 5 times more C60F36 molecules have to be doped into unpurified MeO-TPD films to shift the Fermi-level just above its intrinsic position. This finding is discussed in terms of a statistical model, showing that narrow deep hole-trap states are additionally present in the unpurified host material which are hindering an efficient generation of free charge carriers at molar doping ratios below MR=0.002.