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An excellent candidate for an earth abundant absorber material is WSe2 which can be directly grown as a p-type semiconductor with a band gap near 1.4 eV. In this work we present the structural, optical, and electrical properties of thin film WSe2 grown via the selenization of sputter deposited tungsten films. We will show that highly textured films...
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Low resistivity (~3-24 mOhm.cm) with tunable n- and p-type phase pure Cu2O thin films have been grown by pulsed laser deposition at 25-200 0C by varying the background oxygen partial pressure (O2pp). Capacitance data obtained by electrochemical impedance spectroscopy was used to determine the conductivity (n- or p-type), carrier density, and flat b...
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... Mao et al. [27] similarly developed a WSe 2 thin film to investigate the photoelectric properties of the thin film. Ma et al. [28] also got a similar type of GIXRD pattern. The high intensity of the plane (0 0 2) refers to the orientation of the thin film growth towards the c-axis i.e., growth is perpendicular to the substrate and the same pattern was reported by Jager et al. [12]. ...
Fabrication of thin films of WSe2 is challenging and various methods are being explored. This study investigates the thermoelectric properties of tungsten diselenide thin films. The thin films are fabricated on Si substrates by using two-step processes. Here, the selenization of DC sputtered W thin films was carried out at different temperatures in the range of 400 to 500oC in the steps of 50oC. The crystal structure is found to be hexagonal and crystallite sizes increase with the selenization temperature. The morphology of the thin films selenized at 400oC shows no separated particles while raising the selenization temperature from 450oC to 500 °C uniform distribution of particles is observed. The shape of the particles was found spherical and rod-like. The Raman spectra show four modes: E1g,, A1g, and . Here, is associated with the interlayer interaction. The electrical resistivities of these thin films exhibit the conduction mechanism of the band conduction model. The highest Seebeck coefficient was reported for S500 (-9.15µV/K). Also, the power factor of S500 is the highest i.e. 13.4 Χ 10− 5µW/mK² This study shows the potential use of the selenization process to fabricate the WSe2 thin films and optimize temperature for better thermoelectric properties.
... By performing DFT calculations and employing the Tauc method [28,29], the band gap nature was investigated, focusing on the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO). By carefully examining the alignment of the valence band (VB) and conduction band (CB) energies in momentum space and their coincidence at a specific point, a direct band gap can be identified; conversely, different energy locations in momentum space signify an indirect band gap. ...
... Here, −ℎ ( ) = band to band absorption co-efficient, Si). Our simulation takes the following literature references for ZnSe [40], Si [41] and AlSb [42][43]. The physical parameters have been optimized in such a way that the values can be adopted in commercial scenarios. ...
... Defect densities in the order of 10 11 cm -2 have been considered at the n + -ZnSe/p-Si junction and in the order of 10 10 cm -2 at the p-Si/p + -AlSb interface. The optical absorption values for n + -ZnSe, p-Si and p + -AlSb have been obtained from the following literature sources [40], [41] and [42][43], respectively. The ability to preserve a high built-in potential in the chosen structure of n + -p-p + causes maintaining VOC above 1 V over a long range for the variation in thickness, doping concentration or impurity concentration [29][30]. ...
The impurity photovoltaic effect (IPV) with thallium (TI) impurity has theoretically been investigated in crystalline silicon (c-Si) wafer reigned dual-heterojunction (DH) solar cell that ensures an extended absorption of longer wavelength light with zinc selenide (ZnSe) window and aluminium antimonide (AlSb) back surface layers. The results imply that the incorporation of impurity enhances the photocurrent while the dual-heterojunction ensures the higher VOC of the proposed solar cell structure. The pristine Si (150 µm wafer) solar cell exhibits a power conversion efficiency (PCE) of 35.04% with JSC= 38.85 mA/cm2 and VOC=1.05 V, respectively. On the contrary, the introduction of Tl impurity within the bandgap of absorber enhances the PCE to 44.47%, with a JSC= 48.95 mA/cm2, VOC=1.063 V and FF=85.46%, respectively. This augmentations of the VOC and JSC and hence PCE is originated from the DH structure and longer wavelength light absorption due to impurity-assisted two-step photon upconversion phenomena in the solar cell.
... Recent advancements have made the software adaptable to simulate both crystalline (Si and GaAs families) and amorphous solar cells (a-Si and micromorphous Si). Our simulation takes following literature references for ZnSe [40], Si [41] and AlSb [42][43]. The physical parameters have been optimized in such a way that the values can be adopted in commercial scenarios. ...
... Defect densities in the order of 10 11 cm -2 have been considered at the n+-ZnSe/p-Si junction and in the order of 10 10 cm -2 at the p-Si/p+-AlSb interface. The optical absorption values for 6 n + -ZnSe, p-Si and p + -AlSb have been obtained from the following literature sources [40], [41] and [42][43], respectively. The ability to preserve a high built-in potential in the chosen structure of n+-p-p+ causes maintaining V OC above 1V over a long range for variation in thickness, doping concentration or impurity concentration [29][30]. ...
The impurity photovoltaic effect (IPV) with thallium (TI) impurity has theoretically been investigated in crystalline silicon(c-Si) wafer reigned dual-heterojunction (DH) solar cell that ensures an extended absorption of longer wavelength light with zinc selenide (ZnSe) window and aluminium antimonide (AlSb) back surface layers. The results imply that the incorporation of impurity enhances the photocurrent while the dual-heterojunction ensures the higher V OC of the proposed solar structure. The pristine Si (150 µm wafer) solar cell exhibits a power conversion efficiency (PCE) of 35.04% with J SC = 38.85 mA/cm 2 and V OC =1.05 V, respectively. On the contrary, the introduction of Tl impurity within the bandgap of absorber enhances the PCE to 44.49%, with a J SC = 48.94 mA/cm 2 , V OC =1.06 V and FF=85.45%, respectively. This augmentations of the V OC and J SC and hence PCE is originated from the DH structure and longer wavelength light absorption due to impurity-assisted two-step photon upconversion phenomena in the solar cell.
... The reflectivity at the front and back contact are considered to be 10 % and 90 % respectively, while other properties of the front-contact, back-contact, and working temperature are provided in Table 2. In this simulation, the experimental optical absorption coefficient of the WSe 2 , Cu 2 O:N, and different ETLs are taken from the literature [50,62,63,64,65,66]. The device is irradiated with a standard AM 1.5G solar spectrum at the power of 100 mW/cm 2 . ...
... It is noteworthy that the performance of WSe 2 device with ZnO ETL is slightly improved. Compared with the device using CdS ETL, its PCE has increased by only about 8.6 % (the actual PCE is 22.68 %, which is within close range of the previously reported results [43,50]). The results are very promising, but due to carrier recombination, improper band structure, incomplete absorption, low carrier collection efficiency, etc., there are still losses, so it is very likely to further enrich the device's performance. ...
... where, KT/q is the thermal voltage (0.02586 V at 300 K), μ is the mobility of the carrier in the c-WSe 2 thin films (30 cm 2 V À1 s À1 [50]). According to earlier reports, the lifetime (τ) of minority carriers in the c-WSe 2 film is around 30 ns [60,61]. ...
In recent years, solar cells made of tungsten diselenide (WSe2) have received comprehensive consideration because of their good photoelectric properties. The planar WSe2-based heterojunction solar cell with a preliminary device structure of Au/WSe2/electron transport layer (ETL)/FTO/Al was designed and investigated numerically by SCAPS-1D. CdS ETL is widely used in thin film solar cells (TFSCs). Due to environmental issues and the low band gap (2.42 eV) of CdS ETL, an alternative to CdS ETL was being explored for WSe2 solar cells. In this work, the photovoltaic (PV) performance of the WSe2-based TFSCs with different ETLs were simulated, analyzed and compared, in an attempt to track down a suitable substitute for the CdS ETL. In addition to CdS ETL, ZnO, TiO2 and SnO2 ETLs were independently used to simulate the PV performance of WSe2-based TCSCs. In the wake of analyzing the J-V curves of different cell configurations, SnO2 ETL yielded the best results with PCE of 27.14 % for the single-junction WSe2/SnO2 TFSC. Then, our simulation predicted that the PV performance of the WSe2 device can be improved significantly by using N doped Cu2O as a hole transport layer (HTL). The optimized WSe2 device with SnO2 ETL and Cu2O:N HTL showed an improved PCE of 33.84 % with very good performance stability at higher temperature. Furthermore, this article proposes to use the Au/Cu2O:N/WSe2/SnO2/FTO/Al heterojunction solar cell in bifacial mode and PV performance of the proposed bifacial device have been also studied using SCAPS-1D. Bifacial WSe2 device leads to enhanced PV performance with bifaciality factor for PCE is 83.64 %. Bifacial gain of the proposed device under simultaneous irradiation of 1 sun from the front and 20 % of 1 sun from back side is found to be 13.95 %. Our simulation predicts that the proposed WSe2 bifacial solar cell is capable of converting solar energy into electricity with an efficiency of about 38.38 %.
... For example, the bandgap of WSe 2 is between 1.16 and 1.54 eV, which is similar to the indirect bandgap of visible light absorption. 27 WSe 2 has a higher shear modulus and higher hardness under pressure. 27 WSe 2 is prone to shear under high pressure and, therefore, can be used as a solid lubricant. ...
... 27 WSe 2 has a higher shear modulus and higher hardness under pressure. 27 WSe 2 is prone to shear under high pressure and, therefore, can be used as a solid lubricant. 28 In addition, WSe 2 is considered as a prototype for electrochemical solar cells. ...
Electronic structures of non-twisted and twisted WTe 2 /WSe 2 heterojunction bilayers were investigated using first-principles calculations. Our results show that, for the twisted WTe 2 /WSe 2 heterojunction bilayer, the bandgaps are all direct bandgaps, and the bandgap (K–K) increases significantly when the twist angle is from 0° to 10°. However, when the twist angle is from 11° to 14.2°, the bandgaps are all indirect bandgaps and the bandgap (G–K) significantly reduces. The band structure of the twisted WTe 2 /WSe 2 heterojunction bilayer differs significantly from that of the non-twisted. Twisted WTe 2 /WSe 2 heterojunction bilayers can be seen as a direct bandgap to an indirect bandgap conversion when turned to a certain angle. Interestingly, the bandgap of the WTe 2 /WSe 2 heterojunction bilayer is very sensitive to the change in the twist angle. For example, when the twist angle is 10.5°, a maximum bandgap will appear. However, the minimum bandgap is 0.041 eV at 14.2°. Our findings have important guidance for device tuning of two-dimensional heterojunction materials.
... Recent advancements have made the software adaptable to simulate both crystalline (Si and GaAs families) and amorphous solar cells (a-Si and micromorphous Si). Our simulation takes following literature references for ZnSe [40], Si [41] and AlSb [42][43]. The physical parameters have been optimized in such a way that the values can be adopted in commercial scenarios. ...
... Defect densities in the order of 10 11 cm -2 have been considered at the n+-ZnSe/p-Si junction and in the order of 10 10 cm -2 at the p-Si/p+-AlSb interface. The optical absorption values for 6 n + -ZnSe, p-Si and p + -AlSb have been obtained from the following literature sources [40], [41] and [42][43], respectively. The ability to preserve a high built-in potential in the chosen structure of n+-p-p+ causes maintaining V OC above 1V over a long range for variation in thickness, doping concentration or impurity concentration [29][30]. ...
The impurity photovoltaic effect (IPV) with thallium (TI) impurity has theoretically been investigated in crystalline silicon (c-Si) wafer reigned dual-heterojunction (DH) solar cell that ensures an extended absorption of longer wavelength light with zinc selenide (ZnSe) window and aluminium antimonide (AlSb) back surface layers. The results imply that the incorporation of impurity enhances the photocurrent while the dual-heterojunction ensures the higher VOC of the proposed solar cell structure. The pristine Si (150 µm wafer) solar cell exhibits a power conversion efficiency (PCE) of 35.04% with JSC= 38.85 mA/cm2 and VOC= 1.05 V, respectively. On the contrary, the introduction of Tl impurity within the bandgap of absorber enhances the PCE to 44.47%, with a JSC= 48.95 mA/cm2, VOC= 1.063 V and FF= 85.46%, respectively. This augmentations of the VOC and JSC and hence PCE is originated from the DH structure and longer wavelength light absorption due to impurity-assisted two-step photon upconversion phenomena in the solar cell.
... Several kinds of p-WSe 2 CVD are reviewed by Cheng et al [38]. These CVD methods are likely to produce a real, high-performance solar cell; however, the costs of CVD production may be prohibitive; therefore, alternative film-growth approaches with lower costs, such as drop cast as used in Si soar cells [39], selenization method [40], and low temperature CVD of WSe 2 [41], may be used. However, there are very few reports of the use of WSe 2 as a back surface field (BSF) layer in GeSe solar cells. ...
This article reports the design and computational analysis of an efficient GeSe-based n-ZnSe/p-GeSe/p ⁺-WSe2 dual-heterojunction (DH) thin film solar cell using SCAPS-1D simulation program with physical parameters from the literature. The device has been optimized considering the thickness, doping and defect density of each layer. The optimized device shows an efficiency of ∼42.18% with a short circuit current density, J SC of 47.84 mA cm⁻², an open circuit voltage, V OC of 1.07 V and fill factor, FF of 82.80%, respectively that remains within the Shockley-Queisser limit of a DH solar cell. The raised built-in potential developed between the two interfaces of the devices produces a surpassing V OC. The higher J SC is attributed to the current generated by absorption of sub-band gap photons by a tail-states-assisted two-step photon upconversion mechanism in the WSe2 back surface field layer. These results indicate the potential of manufacturing the high efficiency GeSe-based DH solar cell in future.
... The solar cells were illuminated by the AM 1.5G Table 1, for Si and GaAs, respectively. The optical absorption coefficient data of each semiconductor used in the simulations were taken from the following literature references for ZnSe [34], Si [35], GaAs [36], AlSb [37,38] GaSb [39] and AlAs [40]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 ...
This article demonstrates the novel designs of Si and GaAs wafer-based double-heterojunction (DH) solar cells using SCAPS-1D simulator. Simple five-layer solar cells are proposed here: cells comprised of a cathode metal layer, three layers of semiconductor materials in the III–V, II–VI and group IV families--and a layer of anode metal. The device structures have been optimized for the analysis of the power-conversion efficiency (PCE) of the Si and GaAs solar cells considering high defect densities at and near each heterojunction. The PCEs predicted are 38% and 38.9% for n-ZnSe/p-Si/p ⁺-Al0.8Ga0.2Sb and n-ZnSe/p-GaAs/p ⁺-AlAs0.9Sb0.1 cells, respectively which stay entirely within the PCE limits set by the Shockley–Queisser theory of multi-junction cell. These results reveal that high efficiency and hence cost-effective Si and GaAs wafer-based DH solar cells can be fabricated in the near future.
... The channel length obtained from the source-drain separation is about 10 μm, and the channel width is 10-15 μm ( figure 1(a)). The carrier density of thin film WSe 2 is reported as ≈ 10 17 cm −3 [20] A droplet of ionic liquid (diethylmethyl(2-methoxyethyl)ammonium bis (trifluoromethylsulfonyl)imide; Aldrich) was placed on the WSe 2 flakes using a syringe. A platinum (Pt) coated tip probed the ionic liquid to apply the V g , as Pt electrodes are known to be very stable and inert in electrochemical systems [21]. ...
We present the electrical characteristics of ionic liquid-gated ambipolar WSe2 field-effect transistors (FET) and analyze them graphically using a transport map. With the transport map, the ambipolar I–V characteristics, which have either electrons or holes as the majority charge carriers depending on the bias conditions, were easily divided into the electron and hole conduction regimes. The effect of the drain bias (Vd) on trapped charges is inferred from the decreased offset voltage, which indicates the downward deflection of the channel energy band with the Vd. We confirmed the change of the majority carrier types shown in the transport map by analyzing the output curves, which show a transition from rectifying to saturated behavior. The existence of a relatively thin Schottky barrier for hole conduction is supported by the degradation in the transconductance curves and the variation in Vth with the Vd. These results provide important information for understanding the operating mechanism of ambipolar WSe2 FETs gated by ionic liquids and can be extended to FETs based on other two-dimensional semiconducting materials.
