MgxZn1 xO Research Articles

Enhancement of Cd‐Free All‐Dry‐Processed Cu(In1‐x,Gax)Se2 Thin‐Film Solar Cells by Simultaneous Adoption of an Enlarged Bandgap Absorber and Tunable Bandgap Zn1‐xMgxO Buffer

Attempts to remove environmentally harmful materials in mass production industries are always a major issue and draw attention if the substitution guarantees a chance to lower fabrication cost and to improve device performance, as in a wide bandgap Zn1‐xMgxO (ZMO) to replace the CdS buffer in Cu(In1‐x,Gax)Se2 (CIGSe) thin‐film solar cell structure. ZMO is one of the candidates for the buffer material in CIGSe thin‐film solar cells with a wide and controllable bandgap depending on the Mg content, which can be helpful in attaining a suitable conduction band offset. Hence, compared to the fixed and limited bandgap of a CdS buffer, a ZMO buffer may provide advantages in Voc and Jsc based on its controllable and wide bandgap, even with a relatively wider bandgap CIGSe thin‐film solar cell. In addition, to solve problems with the defect sites at the ZMO/CIGSe junction interface, a few‐nanometer ZnS layer is employed for heterojunction interface passivation, forming a ZMO/ZnS buffer structure by atomic layer deposition (ALD). Finally, a Cd‐free all‐dry‐processed CIGSe solar cell with a wider bandgap (1.25 eV) and ALD‐grown buffer structure exhibited the best power conversion efficiency of 19.1%, which exhibited a higher performance than the CdS counterpart.

Metal oxides for electronics and the SPQEO journal

This article discusses the main trends in the physics and preparation of metal oxides and summarizes the results of research published by SPQEO in this area over the past decade. The main metal oxides studied include ZnO, Zn1-xCdxO, Zn1-xCoxO, MgxZn1–xO, ZnO:Mn, VO2, ZrO2–Y2O3, TiO2, WO3, Gd2O3, Er2O3, WO3–CaO–SiO2–B2O3: Tb3+, Dy2O3, NiO, FexOy, Ga2O3, Al2O3, ITO, Ag2O and graphene oxide. These oxides were obtained by the following methods: sintering in air or in a stream of various gases, magnetron sputtering, atomic layer deposition, explosive evaporation, sol-gel, spin coating, spray pyrolysis, rapid thermal annealing, green synthesis from plant solutions, melt quenching, rapid thermal annealing, self-ignition, ion-plasma co-sputtering, vacuum sputtering, reactive ion beam sputtering, and the Hammer method. The electrical and optical properties of the studied oxides are illustrated.

Strong nonlinear-polarization in ZnMgO epitaxial thin-films with Li incorporation

The second-order nonlinear-polarization originated from the interaction between thin-film materials with second-order nonlinear susceptibility (χ (2)) and high-power laser is essential for integrated optics and photonics. In this work, strong second-order nonlinear-polarization was found in a-axis oriented Zn1-x Mg x O (ZnMgO) epitaxial thin-films with Li incorporation, which were deposited by radio-frequency magnetron sputtering. Mg incorporation (x > 0.3) causes a sharp fall in the matrix element χ 33 of χ (2) tensor, although it widens optical bandgap (E opt). In contrast, moderate Li incorporation significantly improves χ 33 and resistance to high-power laser pulses with a little influence on E opt. In particular, a Zn0.67Mg0.33O:Li [Li/(Zn + Mg + Li) = 0.07] thin-film shows a |χ 33| of 36.1 pm V−1 under a peak power density (E p) of 81.2 GW cm−2, a resistance to laser pulses with E p of up to 124.9 GW cm−2, and an E opt of 3.95 eV. Compared to that of ZnO, these parameters increase by 37.8%, 53.4%, and 18.6%, respectively. Specially, the Zn0.67Mg0.33O:Li shows higher radiation resistance than a Mg-doped LiNbO3 crystal with a comparable E opt. First-principle calculations reveal the Li occupation at octahedral interstitial sites of wurtzite ZnO enhances radiation resistance by improving structural stability. X-ray photoelectron spectroscopy characterizations suggest moderate Li incorporation increases χ 33 via enhancing electronic polarization. These findings uncover the close relationship between the octahedra interstitial defects in wurtzite ZnMgO and its nonlinear-polarization behavior under the optical frequency electric field of high-power laser.

Suppressing interface recombination via element diffusion regulation towards high-efficiency Cd-free Cu(In,Ga)Se2 solar cells

Magnetron-sputtered Zn1-xMgxO (ZMO) films suffer from severe elemental diffusion to Cu(In,Ga)Se2 (CIGS), which limits the further improvement of device performance. Herein, we introduced Zn(O,S) (ZOS) as a barrier layer, and we controlled the diffusion of Zn within an appropriate range by adjusting the annealing temperature of ZOS. The results indicate that Zn can occupy copper vacancies (VCu) in CIGS and easily diffuse through VCu. A moderate amount of Zn at the interface acts as a charge compensator, reducing the band tailing effect and promoting the carrier collection efficiency of photovoltaic (PV) devices. However, excessive Zn doping induces additional defects dominated by ZnCu, ZnGa and ZnIn, leading to severe nonradiative recombination. Consequently, the Cd-free CIGS solar cell produced based on these insights exhibited a 49.4-mV reduction in the Voc deficit (Voc,def) as well as a notable increase in the power conversion efficiency (PCE) to 18.0 %. This study is the first to reveal the mechanism of defects caused by Zn diffusion, and these findings provide theoretical support for the study of Cd-free thin-film solar cells.

The dependence of electrical conductivity of MgxZn1–xO ceramics on phase composition

The structural and electrical characteristics of (Mg,Zn)O ceramics produced using the solid state reaction at 1100 °C for 3 hours were studied applying X-ray diffraction and IR reflection spectroscopy as well as means of direct current measurements versus MgO content in initial charge (varied from 0 to 100 mol.%). It has been shown that electrical conductivity extracted from the IR reflection spectra corresponds to that of hexagonal phase in a solid solution, while plasmon in cubic phase was not observed. The electron concentration in the hexagonal grains of solid solution prepared with MgO content below 30 mol. % in the charge was found to be close to that of ZnO grains. It shows the tendency to decrease with further growth of the MgO content, which was explained by extraction of zinc interstitials, responsible for ZnO conductivity, from ZnO under formation of the MgZnO cubic phase. The direct current measurements have shown the lower conductivity as compared to the value estimated from IR reflection spectra. This fact along with the superlinearity of current-voltage characteristics has been explained by the presence of intergranular barriers, which does not allow obtaining information on the concentration of free electrons in the grain by this method. The possible nature of intergranular barriers as well as the role of grain boundaries in the DC conductivity of samples has been discussed.

A comprehensive study on the influence of Mg doping on structural, AC conductivity, and dielectric behavior of ZnONPs

In this research magnesium (Mg) doped zinc oxide nanoparticles (Zn1-x MgxO, where x = 0 for pure ZnO) were synthesized using a simple chemical route. Their structure and morphology was characterized using different methods, such as X-ray diffraction, scanning electron microscopy, Fourier Transform spectroscopy, photoluminescence. Nanoparticles (NPs) were synthesized and analyzed for their structure, shape, chemical content, and optical and dielectric activity with Zn1-x MgxO (where x = 5,15,50 wt%). The crystalline, hexagonal ZnO was verified by X-ray diffraction, with an average grain size of 45 nm for ZnO and 28 nm for Mg doping and a more interplane spacing that ranges from 2.9 nm to 18 nm. In the nanoscale domain, with a hexagonal crystalline shape between 30 and 80 nm, Zn1-x MgxO were analyzed in scanning electron microscopy (SEM) pictures. Transmittance rises with doping, as shown by optical characterization, and UV–vis spectroscopy reveals low absorbance in the visible area. Absorption values drop dramatically for all samples in the UV region, and when magnesium content rises, the absorption peak moves to shorter wavelengths. As the Mg content increased from 5 % to 50 %, the optical absorption spectra of ZnO switched to red. The UV emission peak in PL spectra was seen between 389 and 700 nm. It revealed that up to 50 % Mg doping, the strength of the emission bands at 405 and 525 nm decreases. According to fluorescence emission, zinc oxide has interaction with porphyrin, which results in a new peak at 389 nm. This 389 nm peak is thus specific to ZnO and Zn1-x MgxO nanoparticles as a result of the electron transport between the two materials. The Zn1-x MgxO samples show low dielectric losses and high dielectric constants in the middle and high-frequency ranges. The Mg doping at 5 % concentration is particularly intriguing since it shows enormous dielectric constant across a broad frequency range. At low frequencies, all the samples suffer from a significant loss factor. In the high-frequency range, it stabilizes.

Energy Band Alignment at p–n Heterojunction Interface in CZTSSe Solar Cells with Novel ZnMgO Buffer Layer

By substituting Zn1−xMgxO (ZMO) for the conventional CdS buffer layer, the CZTSSe solar cells with the efficiency of 11.2% are obtained herein, which can be attributed to the conduction band regulation in the heterojunction. An appropriate conduction band offset (CBO) value can effectively reduce nonradiative recombination loss of charge carriers at the interface, thereby improving the open‐circuit voltage (Voc). Herein, ZMO buffer layer with the optical bandgap ranging from 3.34 to 3.90 eV is applied to enhance the CBO in the heterojunction from 0.14 to 0.72 eV. The ZMO‐buffered solar cells exhibit higher Voc and short‐current density (Jsc) compared to CdS‐buffered cells. The optimal efficiency of 11.2% is obtained in CZTSSe solar cell with the CBO of 0.27 eV, Jsc of 39.0 mA cm−2, fill factor of 69.6%, and Voc of 412 mV.

Applications of spectroscopic ellipsometry for multilayer analysis of CdTe solar cell structures incorporating Magnesium–Zinc oxide high resistivity transparent layers

An optical function parameterization of polycrystalline MgxZn1-xO (MZO) thin films as a function of bandgap Eg has been utilized in applications for the metrology of CdTe-based solar cell structures that incorporate MZO thin films as high resistivity transparent (HRT) layers. Parametric expressions are applied to facilitate mapping spectroscopic ellipsometry (M-SE) of device structures consisting of glass/SnO2:F/MZO. M-SE is shown to provide maps in the MZO effective thickness and bandgap within confidence limits of ± 1 nm and ± 0.003 eV, respectively. As a second application of these parametric expressions, an as-deposited glass/SnO2:F/MZO/CdS/CdTe device structure has been analyzed by through-the-glass spectroscopic ellipsometry (TG-SE). Such an analysis is also shown to provide the MZO effective thickness and bandgap. The outcome of the TG-SE analysis for this device structure enables simulations of the external quantum efficiency (EQE) spectrum of the resulting solar cell assuming different recombination losses within the individual layers of the structure. A comparison of these simulations with the experimental EQE spectrum reveals improved current collection from the front of the device incorporating an MZO HRT layer.

Micro-mechanism study of the effect of Cd-free buffer layers ZnXO (X = Mg/Sn) on the performance of flexible Cu2ZnSn(S, Se)4 solar cell

The traditional CdS buffer layers in flexible CZTSSe solar cells lead to light absorption losses and environmental pollution problems. Therefore, the study of Cd-free buffer layer is very important for the realization of environmentally friendly and efficient CZTSSe solar cells. The Zn1–x Mg x O (ZnMgO) and Zn1–x Sn x O (ZnSnO) alternate buffer layers are studied in this study using the simulation package solar cell capacitance simulator (SCAPS-1D) numerical simulation model, and the theoretical analysis is further verified by the results of the experiments. We simulate the performance of CZTSSe/ZnXO (X = Mg/Sn) heterojunction devices with different Mg/(Zn+Mg) and Sn/(Zn+Sn) ratios and analyze the intrinsic mechanism of the effect of conduction band offsets (CBO) on the device performance. The simulation results show that the CZTSSe/ZnXO (X = Mg/Sn) devices achieve optimal performance with a small “spike” band or “flat” band at Mg and Sn doping concentrations of 0.1 and 0.2, respectively. To investigate the potential of Zn0.9Mg0.1O and Zn0.8Sn0.2O as alternative buffer layers, carrier concentrations and thicknesses are analyzed. The simulation demonstrates that the Zn0.9Mg0.1O device with low carrier concentration has a high resistivity, serious carrier recombination, and a greater impact on performance from thickness variation. Numerical simulations and experimental results show the potential of the ZnSnO buffer layer as an alternative to toxic CdS, and the ZnMgO layer has the limitation as a substitute buffer layer. This paper provides the theoretical basis and experimental proof for further searching for a suitable flexible CZTSSe Cd-free buffer layer.

Effects of absorber near-interface compensation on Cd(Se,Te) solar cell performance

Arsenic (As) has been shown to be an effective p-type dopant for CdTe, although high performance in As-doped devices remains difficult to achieve. Arsenic is prone to self-compensation in CdTe, as evidenced by the accumulation of dopant atoms in CdTe/Cd(Se,Te) near the interface with MgxZn1-xO (MZO). In this study, we use SCAPS 1D modeling software to investigate the effect of near-interface compensation, helping elucidate loss pathways in present-day As-doped devices and informing future growth directions. We consider three possible results of As accumulation: shallow donors, deep recombination centers, and a thin layer of excess acceptor accumulation. The reduction in near-interface carrier concentration caused by shallow donors is shown to improve open-circuit voltages (Voc), whereas deep levels are detrimental to all performance parameters. The thin charge layer affects capacitance-voltage (CV) measurements by reducing the depletion width while maintaining the same carrier concentration, replicating CV behavior that has been observed in actual devices. These results illustrate the importance of monitoring dopant accumulation within 100 nm of the interface, and suggest that reducing or eliminating the As concentration in this region would be beneficial. An undoped Cd(Se,Te) layer at the interface is suggested as a possible device structure to boost performance.

Blocking Si‐Induced Visible Photoresponse in n‐MgxZn1–xO/p‐Si Heterojunction UV Photodetectors Using MgO Barrier Layer

Photodetectors based on n‐Mg0.25Zn0.75O/p‐Si heterojunctions are not only suitable for integration with existing semiconductor technology, but also circumvent the difficulty of stable p‐type doping in MgxZn1–xO. However, the use of Si leads to photoresponse in the visible part of the light spectrum, which renders n‐MgxZn1–xO/p‐Si heterojunction devices unsuitable for visible blind UV photodetection. Herein, it is demonstrated that the visible photoresponse in the n‐Mg0.25Zn0.75O/p‐Si photodetectors can be significantly suppressed by inserting a thin interlayer of MgO at the heterojunction. The MgO layer serves as a blocking layer for the drift of photo‐excited electrons from p‐Si to n‐Mg0.25Zn0.75O, thereby limiting the visible photoresponse. It is found that on increasing the thickness of the MgO interlayer from 3 to 15 nm, the UV to visible rejection ratio increases from ≈25 to 200. This enhancement in the UV to visible rejection ratio demonstrates that n‐Mg0.25Zn0.75O/p‐Si heterojunction devices with MgO interlayer are promising for visible‐blind UV photodetection applications.

Modeling and study of MgZnO/CdZnO MQW LED with p–GaN/AlGaN cladding/EB layer

We propose a multi–quantum–well (MQW) light–emitting–diode (LED) design including p–GaN/p–AlGaN/MgxZn1–xO/CdxZn1–xO/n– MgxZn1–xO /n–ZnO structure. The effect of different Mg and Cd molar fraction, thickness of quantum barrier, number of quantum well and carrier concentration of p–GaN layer on the performance of the proposed structure are studied through 2D simulation by ATLAS. The optimal xMg= 0.22 and xCd= 0.003 is determined through optimization process. Also, the optimal thickness of 5 nm for quantum barrier and the optimal number of 2 quantum wells is achieved for the proposed structure. To increase/decrease as much as possible the internal quantum efficiency/efficiency droop of the device, different affecting parameters are varied. The carrier concentration of p–GaN layer was revealed as the most affecting factor on the increase of quantum efficiency and reduction of the efficiency droop.

Bandgap tunability and local structure of MgxZn1–xO (0 ≤ x ≤ 1) thin films grown by RF magnetron co-sputtering

Bandgap tunability and local structure of MgxZn1–xO (0 ≤ x ≤ 1) thin films grown by RF magnetron co-sputtering

Fabrication of Zn1-xMgxO/AgyO heterojunction diodes by mist CVD at atmospheric pressure

We report on the preparation of heterojunction based on Zn1-xMgxO/p-AgyO semiconductor heterostructure. A series of multi-layers, containing Zn1-xMgxO (ZnMgO) films stacked on InSnO (ITO) films, were prepared using mist chemical vapor deposition system with different flow rates for the Mg carrier gas/dilution gas (c.g./d.g.). AgyO films then were deposited on the ZnMgO/ITO substrates. It was found that as the flow rate of the Mg c.g./d.g. increased, the morphology and crystallinity of the ZnMgO films were extensively impacted by the Mg content and the cross-section images of the ZnMgO/AgyO HJDs showed spontaneous order of the random alloys and partial inclinations of the multi-layers, the band gaps of ZnMgO broadened from 3.3 to 3.7 eV, and resistivity increased to 1.58 × 108 Ω·cm; the work function of AgyO films increased to 5.6 eV at the highest O2 flow rate (R[O2] = 30%) during the sputtering process. Although the energy gap variations caused abrupt interfaces, these ZnMgO/AgyO HJDs demonstrated rectifying behavior with a barrier height of around 0.98 eV, which is comparable to that achieved using similar but more expensive preparation methods.

Mg Content Impact of a Sputtered Zn1–xMgxO:Al Transparent Electrode on Photovoltaic Performances of Flexible, Cd-Free, and All-Dry-Process Cu(In,Ga)(S,Se)2 Solar Cells

Development of flexible, Cd-free, and all-dry-process Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells on stainless-steel (SUS) substrates has been conducted with sputtered Zn0.84Mg0.16O buffer and sputtered Zn1–xMgxO:Al transparent conductive oxide (TCO). The conduction band minimum (EC) difference between the CIGSSe absorber and Zn1–xMgxO:Al TCO layer, which is called ΔEC-TA, is examined as the promising parameter to enhance conversion efficiency (η). According to photoelectron yield spectroscopy, actual valence band maximum (EV) of Zn1–xMgxO:Al is almost constant from −7.54 to −7.57 eV under the increased Mg contents from 0 to 0.19, where the band gap (Eg) is changed from about 3.5 to 3.9 eV, respectively. Namely, Mg content variation in Zn1–xMgxO:Al primarily changes the EC value, thereby giving rise to the adjustment of ΔEC-TA. It is disclosed that ΔEC-TA plays an important role in increasing η. In theoretical results, optimized ΔEC-TA for high performances is in a range from +0.07 to +0.57 eV. In experimental results, the η values are clearly enhanced from 13.7% with a ΔEC-TA of −0.06 eV (for ZnO:Al TCO) to 16.1% (and the highest η of 16.5%) with the optimal ΔEC-TA from +0.16 eV to +0.22 eV (for Zn1–xMgxO:Al TCO) under an optimal Mg content from 0.12 to 0.16, well consistent with the theoretical results.

Luminescence of ZnO/MgO phosphors

Zn1–xMgxO phosphors has been synthesized through solid-state chemical reaction method and their structural and optical properties investigated. XRD results confirm that synthesized samples are polycrystalline with hexagonal wurtzite structure. MgO phase appears for x ≥ 0.2 and becomes dominant when x > 0.6. The absorption edge was found continuously to shift to the shorter wavelength, indicating an increase of the optical band gap with content (x) of magnesium. In addition, the intensity of the emission band drops down with x. At low temperatures, two sets of exciton lines and their phonons were observed. The first one at longer wavelengths may be associated with shallow donors near zinc (Zn) and the second lines at shorter wavelengths may be related with shallow donors near magnesium (Mg). In view of the band gap, Zn1–xMgxO phosphors are a promising material for ultraviolet light emitting devices.

CdTe‐Based Solar Cells with Variations in Mg Concentration in the MgZnO Emitter

The optimal fraction of Mg incorporation in sputter‐deposited MgXZn1−XO (MZO) emitters for thin‐film CdTe‐based solar cells is evaluated by varying it over a range of x from 0 to 0.35. This range allows a variation in the conduction band offset from −0.1 eV (cliff like) to +0.32 eV (spike like). A maximum efficiency of 18.5% for cells with the bilayer CdSeTe/CdTe absorber occurs at x = 0.15, which corresponds to a spike‐like band offset near 0.2 eV, as confirmed by X‐ray photoelectron spectroscopy. In addition, good cell performance is seen over a fairly broad range of x extending from 0.1 to 0.25. The MZO optical bandgap increases with the Mg fraction, consistent with an increasing conduction band offset. Temperature‐dependent current−voltage measurements and time‐resolved photoluminescence show improvement in the emitter/absorber interface with the incorporation of Mg. Capacitance−voltage measurements show that the depletion region extends further into the absorber with more Mg, and X‐ray diffraction confirms a change from a hexagonal‐dominant crystal structure toward zinc blende at x = 0.35.

Effect of Mg doping on morphology, photocatalytic activity and related biological properties of Zn1-xMgxO nanoparticles.

The objective of this study is to synthesize ZnO and Mg doped ZnO (Zn1−xMgxO) nanoparticles via the sol-gel method, and characterize their structures and to investigate their biological properties such as antibacterial activity and hemolytic potential.Nanoparticles (NPs) were synthesized by the sol-gel method using zinc acetate dihydrate (Zn(CH3COO)2.2H2O) and magnesium acetate tetrahydrate (Mg(CH3COO)2.4H2O) as precursors. Methanol and monoethanolamine were used as solvent and sol stabilizer, respectively. Structural and morphological characterizations of Zn1−xMgxO nanoparticles were studied by using XRD and SEM-EDX, respectively. Photocatalytic activities of ZnO and selected Mg-doped ZnO (Zn1−xMgxO) nanoparticles were investigated by degradation of methylene blue (MeB). Results indicated that Mg doping (both 10% and 30%) to the ZnO nanoparticles enhanced the photocatalytic activity and a little amount of Zn0.90 Mg0.10 O photocatalyst (1.0 mg/mL) degraded MeB with 99% efficiency after 24 h of irradiation under ambient visible light. Antibacterial activity of nanoparticles versus Escherichia coli ( E. coli ) was determined by the standard plate count method. Hemolytic activities of the NPs were studied by hemolysis tests using human erythrocytes. XRD data proved that the average particle size of nanoparticles was around 30 nm. Moreover, the XRD results indicatedthat the patterns of Mg doped ZnO nanoparticles related to ZnO hexagonal wurtzite structure had no secondary phase for x ≤ 0.2 concentration. For 0 ≤ x ≤ 0.02, NPs showed a concentration dependent antibacterial activity against E. coli . While Zn0.90Mg0.10 O totally inhibited the growth of E. coli , upper and lower dopant concentrations did not show antibacterial activity.

Zn1−xMgxO second buffer layer of Cu2Sn1−xGexS3 thin-film solar cell for minimizing carrier recombination and open-circuit voltage deficit

Zn1−xMgxO (ZMO) second buffer was applied to replace conventional ZnO second buffer layer of Cu2(Sn,Ge)S3 (CTGS) solar cells to reduce interface carrier recombination and open-circuit voltage deficit (VOC,def). Structure of the solar cell is glass/Mo/CTGS/CdS first buffer/ZMO second buffer/ZnO:Al (AZO)/Ni-Al. Bandgap energy (Eg) of the ZMO films is changed from 3.20 to 3.65 eV by varying Mg/(Mg + Zn) ratio from 0 (for pure ZnO) to 0.26. The increase in the Eg of ZMO films is attributable to the move of conduction band minimum (EC). It is determined that ZMO second buffer with increase in Eg from 3.20 to 3.55 eV yields the smoothing conduction band offset (CBO) at ZMO/CdS interface varying from −0.26 to +0.09 eV. Saturation current density (J0) is therefore reduced to the lowest value, and activation energy of recombination (EA) is the closet to the Eg of the CTGS absorber layer, implying the lowest interface carrier recombination (reduced VOC,def), and thereby increasing conversion efficiency (η) to 4.5% (Eg of ZMO: 3.55 eV). On the other hand, the ZMO second buffer with Eg larger than 3.55 eV results in the CBO at ZMO/CdS interface of +0.19 eV (Eg of ZMO: 3.65 eV), making the well of EC structure in ZMO/CdS/CTGS stacking layers, thus increasing interface carrier recombination, and severely decreasing the η to about 0.2%.

Enhanced efficiency of quantum dot light-emitting diode by sol-gel derived Zn1-xMgxO electron transport layer

Abstract In this study, sol-gel derived Zn1-xMgxO (ZMO) is proposed as an electron transport layer (ETL) for solution-processed quantum-dot light-emitting diodes (QLEDs). It is demonstrated that the increase of Mg content in Zn1-xMgxO films from 0% to 20% causes a dramatic suppression of electron current, which is attributed to the lifting of conduction band minimum and reduction of electron mobility. As a result of Mg-doping, the charge carrier balance might be achieved in the QLED with the Zn0.85Mg0.15O layer resulting in maximum external quantum efficiency of 5.74% and current efficiency of 18 cd A−1, which are over 3-fold higher than in the case of the device with ZnO layer. Improved device performance is further explained by reduced exciton quenching at QDs/ZMO interface, which is confirmed by time-resolved PL experiments. Obtained results indicate that sol-gel derived ZMO is a promising candidate for ETL in quantum-dot based optoelectronic devices.