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Zn1−xMgxO/Cu2O heterojunctions were successfully fabricated in open-air at low temperatures via atmospheric atomic layer deposition of Zn1−xMgxO on thermally oxidized cuprous oxide. Solar cells employing these heterojunctions demonstrated a power conversion efficiency exceeding 2.2% and an open-circuit voltage of 0.65 V. Surface oxidation of Cu2O t...
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... the intrinsic nature of p-type con- ductivity in Cu 2 O makes the formation of a homojunction, and hence achieving maximum efficiency, difficult [2]. Most of the research effort has therefore been focused on heterojunction solar cells, pairing Cu 2 O with ZnO and its doped variations (see Table 1), although other wide band gap oxides such as In 2 O 3 :Sn (ITO), Ga 2 O 3 and TiO 2 have been investigated as well [3,4]. Fig. 1 and Table 1 present developments in Cu 2 O-based solar cell research over the past few years. ...
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... of the research effort has therefore been focused on heterojunction solar cells, pairing Cu 2 O with ZnO and its doped variations (see Table 1), although other wide band gap oxides such as In 2 O 3 :Sn (ITO), Ga 2 O 3 and TiO 2 have been investigated as well [3,4]. Fig. 1 and Table 1 present developments in Cu 2 O-based solar cell research over the past few years. One can note that the efficiencies and the open-circuit voltages of the devices have varied widely depending on the synthesis method used. ...
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... 2 O solar cells made with ZnO films deposited under standard ZnO AALD conditions (see Table 2 and Fig. 6, "standard") exhibited poor performance as compared to the values reported in literature for cells made by other methods (Table 1). The low open- circuit voltage in these devices was attributed to the presence of CuO and other copper compounds between the Cu 2 O and ZnO layers. ...
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... lower V oc s observed in Fig. 7(b) for ZnO deposited at 50 1C may be explained by the platen temperature not being sufficiently high for precursors to react on the substrate surface, leading to the ZnO film having poorer carrier properties. The best ZnO/Cu 2 O solar cell was obtained with ZnO deposited at 100 1C for 100 s, and showed a 6-fold higher power conversion efficiency of 1.46% (see Figs. 1 and 6, Tables 1 and 2) for an optimized sample as compared to a standard ZnO/Cu 2 O device. This performance is comparable with the MgF 2 /ITO/ZnO/Cu 2 O solar cell reported by Mittiga et al. [6], who deposited ZnO by ion beam sputtering on thermally oxidized Cu 2 O. On the contrary, in this work, the heterojunction interface was formed outside a vacuum. ...
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Citations
... 7 The typical structure of an all-oxide solar cell, shown in Figure 1, involves different layers, each with specific requirements: (i) back contact on glass substrate; (ii) p-doped absorber layer with high absorption coefficient optimally matching the solar spectrum; (iii) n-doped buffer layer forming the pn junction with the absorber with an optimal band alignment; (iv) highly transparent window layer with optimal conductivity; (v) top contact that can be a TCO with high conductivity and high transparency in order to extract the generated charges. Research by Ievskaya et al. 8 focused on ZnO/Cu 2 O heterojunction fabricated using the ALD (Atomic Layer Deposition) technique, obtaining an efficiency of 2.2 %. Indeed, Minami et al. 9 investigated three different structures of all-oxide solar cells: ZnAlO/ZnMgO/Cu 2 O, ZnAlO/Cu 2 O and ZnAlO/ZnO/Cu 2 O using PLD (Pulsed Laser Deposition) technique to deposit ZnO, ZnAlO and ZnMgO. ...
... ZnO-based heterostructures have nonetheless seen significant progress in significantly enhanced thermoelectric properties and achieving a high zT: ZnO/Cu 2 O heterostructures emerge as one of the most promising devices with significant potential in the future generations of the thermoelectricity modules [29]. These heterostructures were successfully fabricated in open-air at low temperatures via atmospheric atomic layer deposition [30][31][32] ...
In this study, we have performed Density Functional Theory calculations of ZnO, Cu2O, and ZnO/Cu2O heterostructures. First, we investigated the structural properties of ZnO and the three polymorphs of Cu2O named cubic, tetragonal, and hexagonal. To build a supercell of ZnO/Cu2O, we have justified that the structure of Cu2O(111) which grows on ZnO is a hexagonal structure. Second, we calculated and analyzed the electronic band structures and the density of states of ZnO, Cu2O polymorphs, and ZnO/Cu2O. Finally, to explore the thermoelectric properties of ZnO, Cu2O polymorphs, and ZnO/Cu2O, we combine all Density Functional Theory and Boltzmann transport theory
... Photovoltaic performance of η = 1.67% and V oc = 0.55V were obtained for the Zn 1−x Mg x O (x = 0.1) based solar cell with Cr/ITO/Cu 2 O/Zn 1−x Mg x O/AZO device structure [18]. Further, an efficiency as high as η = 2.2% with V oc = 0.65V was achieved in ITO/Zn 0.79 Mg 0.21 O/Cu 2 O solar cell device through the use of an electrodeposited Cu 2 O thin films as active layers [19]. Even better results were reported for AZO/Zn 0.91 Mg 0.09 O/Cu 2 O heterojunction cells reaching an efficiency of η = 4.31%, using thermally oxidized copper (Cu) sheets as active layers and AZO and Zn 0.91 Mg 0.09 O layers prepared by pulsed laser deposition method. ...
This study describes the fabrication of p-Cu2O/n-MZO/FTO heterojunctions by using a simple two-step electrodeposition method. Electronic, microstructural, morphological, optical, and electrical properties have been systematically investigated by using a variety of analysis techniques. Mott–Schottky analysis indicated p-type conductivity for Cu2O and n-type conductivity for ZnO. Analysis revealed the decrease of the conduction band offset at the Cu2O/MZO interface with the contribution of Mg doping approach, which accounts for the upward movement of the conduction band edges of MZO layers. X-ray diffraction indicated that Cu2O and ZnO films were polycrystalline in nature with strong cubic Cu2O(111) and wurtzite ZnO(002)-oriented phases. Morphological analyses revealed that Mg doping could produce finer microstructures and improve the surface flatness of films. The optical measurement indicated that Mg doping enable the band gap engineering of ZnO films and the design of high-performance photovoltaic window layers. Current–voltage plots showed that Au/p-Cu2O/n-ZnO(MZO)/FTO heterojunctions exhibited an excellent rectifying behavior and their electrical performance can be effectively controlled by using Mg doping approach.
... Among these oxides, cuprous oxide (Cu 2 O) is considered as one of the most promising p-type semiconductor materials, particularly for photovoltaic applications, thanks to its native p-type semiconductivity, its high majority carrier mobility, and its optical transparency [4][5][6]. As a result, over the past decade, many Cu 2 O-based solar cells that incorporated various n-type semiconductors with large band gap energy, such as aluminum-doped zinc oxide (AZO), have been fabricated with a power conversion efficiency (PCE) between 0.24 % and 3.21 % [7][8][9][10][11]. Despite efforts to fabricate high-performance Cu 2 O/AZO heterojunction solar cells, the achieved efficiencies remain significantly lower than the theoretical limit of 20 %, based on the Cu 2 O band gap [12]. ...
In the present work, titanium dioxide (TiO2) is sandwiched as a buffer layer between n-type aluminum-doped zinc oxide (AZO) and p-type cuprous oxide (Cu2O), increasing the efficiency of metal oxide-based solar cells. The effects of the device parameters such as thicknesses, carrier concentrations, and defect densities were investigated by numerical simulation to obtain optimal performance of Cu2O-based solar cells. Our findings reveal that by the incorporation of TiO2 thin film, the efficiency of the solar cell increases remarkably from 2.54 % to 5.02 %. The optimal thicknesses of the Cu2O and TiO2 layers are in the range of 10 μm and 0.1 μm, respectively. We obtained optimal photo-electric conversion efficiency of 10.17 % and open-circuit voltage of 1.35 V while achieving 8.90 mA/cm2 short-circuit current density and 84.12 % fill factor, using structure parameters of 0.2 μm AZO, 0.1 μm TiO2 and 10 μm Cu2O with optimal acceptor-type dopant density in Cu2O of 1E17 cm-3 and donor-type dopant density in TiO2 of 1E18 cm-3.
... Cu 2 O-based solar cell efficiency latest developments (until 2014). This table is based on that proposed by Ievskaya et al.[47]. ...
PV technology offers a sustainable solution to the increased energy demand especially based on mono- and polycrystalline silicon solar cells. The most recent years have allowed the successful development of perovskite and tandem heterojunction Si-based solar cells with energy conversion efficiency over 28%. The metal oxide heterojunction tandem solar cells have a great potential application in the future photovoltaic field. Cu2O (band gap of 2.07 eV) and ZnO (band gap of 3.3 eV) are very good materials for solar cells and their features completely justify the high interest for the research of tandem heterojunction based on them. This review article analyzes high-efficiency silicon-based tandem heterojunction solar cells (HTSCs) with metal oxides. It is structured on six chapters dedicated to four main issues: (1) fabrication techniques and device architecture; (2) characterization of Cu2O and ZnO layers; (3) numerical modelling of Cu2O/ZnO HTSC; (4) stability and reliability approach. The device architecture establishes that the HTSC is constituted from two sub-cells: ZnO/Cu2O and c-Si. The four terminal tandem solar cells contribute to the increased current density and conversion efficiency. Cu2O and ZnO materials are defined as promising candidates for high-efficiency solar devices due to the morphological, structural, and optical characterization emphasized. Based on multiscale modelling of PV technology, the electrical and optical numerical modelling of the two sub-cells of HTSC are presented. At the same time, the thermal stability and reliability approach are essential and needed for an optimum operation of HTSC, concerning the cell lifetime and degradation degree. Further progress on flexible HTSC could determine that such advanced solar devices would become commercially sustainable in the near future.
... The hetero-junction structure of Cu 2 O-based PV devices has been demonstrated to substantially improve PV performance. Cu 2 O-based PV devices with n-ZnO and p-Cu 2 O have been designed and fabricated recently [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The junction interface of these films has been established as an essential factor to influence the PV performance. ...
... The use of ZnO and Cu 2 O to produce PV devices has been extensively studied. Various approaches for the fabrication of ZnO and Cu 2 O films have been proposed, such as chemical vapor deposition [10,11], sputtering [12][13][14][15][16][17][18][19][20][21][22][23][24], thermal oxidation [15,16], and electrochemical deposition (ECD) [17][18][19][20][21][22][23][24][25][26][27]. The properties of ZnO and Cu 2 O films (e.g., crystallinity, morphology, and conductivity) and ZnO/Cu 2 O interface are affected by the fabrication method. ...
... The use of ZnO and Cu 2 O to produce PV devices has been extensively studied. Various approaches for the fabrication of ZnO and Cu 2 O films have been proposed, such as chemical vapor deposition [10,11], sputtering [12][13][14][15][16][17][18][19][20][21][22][23][24], thermal oxidation [15,16], and electrochemical deposition (ECD) [17][18][19][20][21][22][23][24][25][26][27]. The properties of ZnO and Cu 2 O films (e.g., crystallinity, morphology, and conductivity) and ZnO/Cu 2 O interface are affected by the fabrication method. ...
Herein, we designed and fabricated photovoltaic (PV) devices with optimal efficiency of Cu2O buffer layers (p-Cu2O/n-Cu2O/ZnO and p-Cu2O/p⁻-Cu2O/ZnO) through electrochemical deposition (ECD) processing. PV devices with two types of buffer layers, n-Cu2O and p⁻-Cu2O, were produced by ECD and consisted of a layer of nanorod ZnO on ITO, an n-Cu2O or a p⁻-Cu2O buffer layer, a p-Cu2O layer, and a sputtered Ag layer. Results revealed that the interface between the ZnO film and the Cu2O buffer, and thickness of the buffer layer were crucial factors to affect PV device performance. The nanorod structure of ZnO transformed into a flake structure during the ECD of n-Cu2O on ZnO. However, ZnO retained the same morphology during the ECD of p⁻-Cu2O on ZnO. The optimal thicknesses of the Cu2O buffer in the PV device were obtained to enhance the PV efficiency from 0.046 (p-Cu2O/ZnO) to 0.17% (p-Cu2O/p⁻-Cu2O/ZnO). The p-Cu2O/ZnO PV performance was improved through the fabrication and incorporation of Cu2O buffers.
Graphical abstract
... In early times, the efficiencies of photovoltaic devices using this oxide were way from this prediction, reporting values below 2%. Fortunately, its efficiency has increased in recent reports: Mittiga et al. [22] have reported a 2% efficiency for an MgF 2 /ITO/ZnO/Cu 2 O heterojunction, using thermal oxidation of copper; Minami et al. [23] have developed an AZO/n--Ga 2 O 3 /p-Cu 2 O from thermally oxidized copper sheets and obtained a 5.38% efficiency; Ievskaya et al. [24] have used atmospheric atomic layer deposition to make a Zn 0.79 Mg 0.21 O/Cu 2 O heterojunction with η=2.2%; Fujimoto et al. [25] have used electrodeposition to develop an FTO/ZnO/Cu 2 O/Au device with η=1.43%. ...
This work presents the fabrication of Cu2O thin films using electrodeposition at room temperature. These have been grown using a copper (II) sulfate electrolyte (pH=10) over the top of fluorine-doped tin oxide films. Thermal oxidation at standard atmosphere was applied to obtain CuO samples from Cu2O. The characterization of these copper oxide samples has revealed their morphological, compositional, crystalline, vibrational, and optical properties. The results should present the desired features for photovoltaic conversion applications. For this, their photocathodic current generation has been tested from the photoelectrochemical (chronoamperometry) technique. In addition, first-principles calculations based on generalized gradient approximation, in a Perdew-Burke-Ernzerhof parametrization, were performed to determine the structural, electronic, and optical properties of these copper oxides. These have helped the interpretation of the experimental results for these samples.
... The minority carriers have a greater distance to diffuse through to the depletion layer, and thus a smaller thickness is suitable while inducing illumination from this side to avoid recombination. Above 475 nm, the carriers are generated 4,9,12,54 deeper and, therefore, closer to the depletion region, which increases their probability to be collected. On the other hand, the bifacial illumination shows a high and constant EQE between 350 and 530 nm. ...
... Figure 8a shows the external quantum efficiency of the reference cell shown previously (Figure 2) with respect to experimental ZnO/Cu 2 O solar cell reported in the literature. 4,9,12,54 Ievskaya et al., Lee et al., and Zang have demonstrated that oxidation of a Cu 2 O surface due to the post-annealing process induces a defect at the interface and thus limits the output results. 9,12,54 Zang has also shown that the orientation of the film improves the diffusion length and therefore the output performance of the cell. ...
... 4,9,12,54 Ievskaya et al., Lee et al., and Zang have demonstrated that oxidation of a Cu 2 O surface due to the post-annealing process induces a defect at the interface and thus limits the output results. 9,12,54 Zang has also shown that the orientation of the film improves the diffusion length and therefore the output performance of the cell. 12 The effect of these parameters is observed in the evolution of the EQEs in Figure 8a with respect to the simulated results, especially in the dark purple and gray regions. ...
... In the literature, there are numerous preparation methods for Cu 2 O thin films, which include both chemical [7][8][9] and physical processes [10][11][12]. Few of the most commonly followed techniques include electrodeposition [13][14][15], thermal oxidation [16][17][18], magnetron sputtering [19][20][21] and, atomic layer deposition (ALD) [22][23][24]. Pulsed laser deposition (PLD) is another physical technique for high quality film deposition. ...
Cuprous oxide materials are of growing interest for optoelectronic devices and were produced by several chemical and physical methods. Here, we report on the structural, optical, and electrical properties of CuxO thin films prepared by the pulsed laser deposition technique. The substrate temperature, as well as the oxygen partial pressure in the deposition chamber, were varied to monitor the copper to oxygen ratio within the deposited films. The growth conditions were carefully optimized to provide the highest conductivity and mobility. Thus, 100 nm thick cuprous oxide films (Cu2O) deposited at 750 °C exhibited a resistivity of 16 Ω∙cm, high mobility of 30 cm²/(V∙s), and a bandgap of around 2 eV. The film deposited at the optimized deposition parameters on Nb:STO (001) substrate with Au top electrode showed a photovoltaic response with an open circuit voltage of 0.56 V. These results path the way to efficient solar cells made with Cu2O films via the pulsed laser deposition technique.
... Despite the significant effort being focused on cell efficiency improvement, the device stability/degradation issues have not yet been completely resolved [20]. So far, there are various methods have been used for the preparation of ZnO and CuO thin films such as sputtering [21][22][23], Solvothermal [24], Spray pyrolysis [25], Electron beam evaporation [26], chemical vapor deposition, and hydrothermal [27], Electrodeposition [28,29], pulsed laser deposition [30], Sol-gel and Doctor-blading [31], thermal evaporation [32], and spin coating [33], etc. Among them, the spin coating provides good quality and uniform deposition suitable for various applications in research and industries [34,35]. ...
Facile synthesis of completely inorganic Zinc oxide-Copper oxide (ZnO-CuO) based bulk heterojunction solar cells (BHJSCs) along with the impact of the film thickness on the different properties like morphological, structural, chemical, optical and electrical have been reported in this work. A simple spin-coating technique was used to fabricate the BHJSC. The elemental presence of ZnO and CuO with wurtzite and cubic phase was confirmed by EDX and XRD analysis correspondingly. The surface quality, optical transmittance and the resistivity of spin-coated BHJ films decrease with increasing the the film thickness revealed by morphological, optical and electrical study respectively. The photovoltaic parameters of FTO/ZnO-CuO/Al heterostructure SC like efficiency η, current density J sc and fill factor also decreased conspicuously, whereas the open circuit voltage was found to increase conversly. Moreover, experimental outcomes indicate, the thickness of the film has inescapable impact on inorganic BHJSCs performances and must take in consideration during cell fabrication.
