Junction Solar Cells Research Articles

Design and optimization of two-terminal InGaP/Si tandem solar cell through numerical simulation

Abstract The III-V/Si double junction solar cells demonstrate cost-effective performance comparable to III-V/III-V tandems, with an efficiency of 35.9%, below the 43% theoretical limit. Considering monolithic InGaP//Si based tandem solar cell, this work dealt with the optimization of its efficiency as a function of layer thicknesses and dopings. Considering ideal optoelectronic parameters of materials, numerical simulations were performed by using Silvaco/ATLAS TCAD software. They were conducted within the context of a multi-step optimization procedure that was proposed in this work. The obtained optimum tandem InGaP//Si structure reached an unprecedented power conversion efficiency of 40.74% under 1.5G spectrum.

The advantages of employing i-a-SiOX:H as a buffer layer in hydrogenated amorphous silicon oxide solar cells

Abstract This study focuses on a p-i-n single junction solar cell made of hydrogenated amorphous silicon oxide (a-SiOx:H), aiming to enhance solar cell efficiency by mitigating the impact of discontinuities and mismatches occurring at the i/p defect-rich interface between the window layer and the absorber layer. To address this concern, the impact of adding a thin i-a-SiOx:H buffer layer between the p-a-SiOx:H window layer and the i-a-SiOx:H active layer was investigated through numerical modeling using the AMPS-1D (Analysis of Micro-electronic and Photonic Structures) computer program. Implementing these changes led to a remarkable increase in conversion efficiency, rising from 5.714% to an impressive 8.929%. The increase in short-circuit current (JSC), however, is due to improved quantum efficiency at short wavelengths between 350 and 550 nm. Furthermore, enhancing the built-in potential (Vbi) at the i/p interface, combined with the buffer layer’s appropriate band gap energy, increases VOC (open-circuit voltage) from 850 to 993 mV. The substantial improvement in the fill factor (FF) from 63.1 to 83.1% can be largely attributed to the smoothed band offset, primarily facilitated by the presence of the buffer layer at the p/i interface, which led to more efficient extraction of photogenerated holes. To ensure effective usage of the buffer layer, the thickness of a-SiOx:H (buffer layer) varied between 3 nm and 9 nm, while the p-type doping concentration of the same layer was adjusted between 0 and 1020 cm−3. In summary, adding a 3 nm thick a-SiOx:H buffer layer with an intermediate band gap and with a p-type doping concentration (NA) below 1018 cm−3 at the i/p interface improves the electrical and optical properties of the p-i-n solar cells (EFF = 8.951%; VOC = 0.994 V; FF = 83.1%; JSC = 10.842 mA.cm−2).

High efficiency homojunction tandem organic solar cells with all solution processable interconnect layer

In the field of organic photovoltaics, the power conversion efficiency of single junction solar cells continues to improve. However, tandem organic solar cells are poised to push the efficiency limits even further and offer a promising avenue for improving the performance of organic photovoltaic devices. This study reports the development of an all-solution processed interconnecting layer (ICL) based on ZnO NPs:PEI/PEI/PEDOT:PSS/2PACz for tandem solar cells. The PM6:BTP-eC9 active layer material was adjusted for its donor-to-acceptor (D/A) ratio and film thickness as the front and back sub-cells. The ICL exhibits favorable mechanical, electrical and optical properties. Through multidimensional modulation, the front and rear sub-cells have been optimized to obtain highly efficient homojunction tandem solar cells. The tandem solar cell has a structure of indium tin oxide (ITO)/PEDOT:PSS/2PACz/active layer/ICL/active layer/PNDIT-F3N/Ag. This optimization resulted in a power conversion efficiency (PCE) of 19.9 %, which is the highest reported efficiency for homojunction tandem organic solar cells to date. Our research demonstrates that the PCE of homojunction tandem cells can be significantly improved by careful design of the interconnecting layers and optimization of the donor-to-acceptor (D/A) ratio. This strategy may provide guidance for further improvements in homojunction tandem cells.

Bending deformation effects on the optoelectronic performance of flexible GaInP/GaAs/InGaAs triple junction solar cells

To achieve genuine carbon neutrality, PV-powered vehicles show promise for future automotive development. However, the impact of curved surfaces on flexible solar cell module performance remains uncertain. This study specifically focuses on newly-designed flexible GaInP/GaAs/InGaAs triple junction solar cells, which have the highest potential output efficiency. A computational model was developed to analyze the electrical performance of curved solar cells, and variations in short-circuit current (Isc) and open-circuit voltage (Voc) with bending angles were determined to closely match experimental data. The effects of incident light intensity, angle, and bending strain on solar cell performance were analyzed to explain the observed Isc and Voc trends. This method can be applied to other III-V group solar cells, providing theoretical support for accurately calculating the performance of curved solar cell modules.

Regulating crystallization and retarding oxidation in Sn-Pb perovskite via 1D cation engineering for high performance all-perovskite tandem solar cells

All-perovskite tandem solar cells have the potential to surpass the theoretical efficiency limit of single junction solar cells by reducing thermalization losses. However, the challenges encompass the oxidation of Sn2+ to Sn4+ and uncontrolled crystallization kinetics in Sn-Pb perovskites, leading to nonradiative recombination and compositional heterogeneity to decrease photovoltaic efficiency and operational stability. Herein, we introduced an ionic liquid additive, 1-ethyl-3-methylimidazolium iodide (EMIMI) into Sn-Pb perovskite precursor to form low-dimensional Sn-rich/pure-Sn perovskites at grain boundaries, which mitigates oxidation of Sn2+ to Sn4+ and regulates the film-forming dynamics of Sn/Pb-based perovskite films. The optimized single-junction Sn-Pb perovskite devices incorporating EMIMI achieved a high efficiency of 22.87%. Furthermore, combined with wide-bandgap perovskite sub-cells in tandem device, we demonstrate 2-terminal all-perovskite tandem solar cells with a power conversion efficiency of 28.34%, achieving improved operational stability.

Translucent Si Solar Cells Patterned with Pulsed Ultraviolet Laser Beam

We report an application of a pulsed ultraviolet (UV) laser (λ = 355 nm) in producing translucent Si solar cells. This process efficiently generates a densely packed microhole array on a fully fabricated Si P‐N junction solar cell in just a few minutes. Herein, prototype cells with a nominal microhole diameter of 23 μm with a spacing between 60 and 300 μm are fabricated. High‐resolution electron‐beam microscopy reveals that the UV laser beam introduces amorphized silicon oxide (SiOx) in proximity to the patterned microholes via localized heating in air. Quantitative photovoltaic (PV) analysis shows a decline in the open‐circuit voltage (Voc) and the fill factor (FF) of the cells with the increase in the microhole density, likely due to the P‐N junction damage during the laser beam irradiation. Despite the reduction in Voc and FF, the solar cells retain a short‐circuit current density (Jsc) above 90% without post‐processing. The inherent microhole geometry associated with the laser beam profile allows multiple light scattering within the confined microhole structure, enhancing the translucency of the cells. While further development is required for optimization, these findings support the potential use of UV laser beams for fast and scalable production of translucent solar cells.

Characterization of MoS2:Nb sputtered thin films. An application as hole transport layer in Cu2ZnSnS4/Si tandem solar cells

MoS2:Nb films deposited by radio-frequency magnetron sputtering are investigated in view of their application in infrared (IR)-transparent contacts for tandem photovoltaic devices.This material is already known to give a good electrical contact with p-type chalcogenide semiconductors, which are typically grown onto opaque molybdenum metallic contacts and a MoS2 layer spontaneously forms at the back interface during the on-top semiconductor growth. Our study explores a different approach, which involves the direct growth of IR-transparent MoS2:Nb films via sputtering inside complete photovoltaic devices, like Cu2ZnSnS4 (CZTS)-based single junction solar cells and CZTS/Si tandem devices. Films deposited at different sputtering pressures are compared by analysing their microstructure, morphology, chemical composition, optical and electrical properties. The effects of post-deposition sulfurization treatments are also investigated. We find that MoS2:Nb films deposited at around 0.1 Pa exhibit compactness but show a notable sulfur deficit ([S]/[Mo]≈1.4), a significant sub-bandgap optical absorptance and lack of crystallinity. Increasing the Ar pressure to 1 Pa raises the [S]/[Mo] ratio to 2.2, yielding crystalline films with good IR-transparency, although with a porous morphology. Despite 0.5 wt% Nb-doping of the sputtering target, the as-deposited films demonstrate n-type conductivity likely due to uncontrolled impurities and intrinsic defects. Ultraviolet Photoemission Spectroscopy measurements suggest that films’ work function higher than 5 eV can be obtained with a post-deposition sulfurization, making these materials suitable as Hole Transport Layer in photovoltaic applications. A similar increase in work function is expected in the CZTS/MoS2 junctions, since the sputtered MoS2:Nb films undergo a sulfurization process needed to obtain the overlying polycrystalline CZTS absorber.CZTS solar cells produced with sputtered MoS2 and Transparent Conductive Oxides contacts on glass substrates, despite plagued by severe adhesion problems, show the potentiality to give efficiencies comparable to reference devices with standard Mo back contact. Fabrication of CZTS/Si tandem devices on textured silicon bottom cells yields a maximum efficiency of 4.4 %, primarily hindered by the low quality of the CZTS film on textured substrates. Nonetheless, optoelectronic characterizations based on both spectrophotometric and quantum efficiency measurements confirm a good IR transparency of the MoS2-based intermediate contacts and the desired electrical behaviour.

Impact of using dual back surface field layers of different materials on GaAs single junction solar cell performance

This research aspires to investigate the impact of employing dual BSF layers on the performance of single junction GaAs solar cells using the Silvaco TCAD simulator. A layer of GaAs, InGaP, and InAlGaP has been implemented as a second BSF layer on top of the original BSF layer of the n-InGaP/n-GaAs/p-GaAs/p-InAlGaP structured solar cell. The results show that using GaAs as a second BSF layer has increased the carrier’s recombination and degraded the cell efficiency due to its lower energy bandgap, which creates a potential well that lessens the number of photogenerated carriers flowing through the conduction band toward electrodes. However, adding InGaP and InAlGaP as a second BSF layer decreases the recombination rate and generates a broad electric field region leading to extra photogenerated carriers drifting through the cell, which increases the efficiency from 29.42% to 29.81% for the case of using InGaP and 30.33% for the case of using InAlGaP. Furthermore, increasing the thickness and doping of the second BSF layer reduces the carriers’ recombination at the boundaries of this layer, which implies efficiency enhancement.

Quantum Interference at the Recombination Junction of Perovskite-Si Tandem Solar Cells Improves Efficiency.

We show quantum interference effects can enhance coherent electron transmission in perovskite tandem solar cells using ultrathin indium tin oxide (ITO) layers. We develop a model for the behavior of the power conversion efficiency based on a finite difference time domain solution of the time-dependent Schrödinger equation. The modeled potential includes an imaginary part to simulate probability loss by incoherent scattering. The results agree with observations of efficiency as a function of ITO thickness, suggesting an optimized design.

Synthesis and Processing Strategy for High-Bandgap PbS Quantum Dots: A Promising Candidate for Harvesting High-Energy Photons in Solar Cells.

The wide tunability of the energy bandgap of colloidal lead sulfide (PbS) quantum dots (QDs) has uniquely positioned them for the development of single junction and tandem solar cells. While there have been substantial advancements in moderate and narrow bandgap PbS QDs-ideal for single junction solar cells and the bottom cell in tandem solar cells, respectively; progress has been limited in high-bandgap PbS QDs that are ideally suited for the formation of the top cell in tandem solar cells. The development of appropriate high bandgap PbS QDs would be a major advancement toward realizing efficient all-QD tandem solar cells utilizing different sizes of PbS QDs. Here, we report a comprehensive approach encompassing synthetic strategy, ligand engineering, and hole transport layer (HTL) modification to implement high-bandgap PbS QDs into solar cell devices. We achieved a greater degree of size homogeneity in high-bandgap PbS QDs through the use of a growth retarding agent and a partial passivation strategy. By adjusting the ligand polarity, we successfully grow HTL over the QD film to fabricate solar cells. With the aid of an interface modifying layer, we incorporated an organic HTL for the realization of high-performance solar cells. These solar cells exhibited an impressive open-circuit voltage of 0.824 V and a power conversion efficiency of 10.7%, marking a 360% improvement over previous results.

Impact of Perovskite Subcell Breakdown on the Performance of Perovskite/Perovskite/Silicon Triple‐Junction Solar Cells

Perovskite‐based triple‐junction solar cells have recently gained significant attention and are rapidly developing, thanks to the insights gained from the advancement in its dual‐junction counterparts. However, employing perovskite materials in multijunction solar cells with more than two junctions brings new challenges that have not yet been addressed. One aspect is the possibility of reverse bias breakdown of perovskite subcells during operation of the triple–junction device. This is more relevant for triple‐junction solar cells because a higher reverse voltage might drop at perovskite subcells compared to the case of dual‐junction solar cells. Herein, the breakdown voltages of the two perovskite subcells in perovskite/perovskite/silicon triple‐junction solar cells are determined by progressively increasing the reverse bias applied to the subcells in a single‐junction architecture during current–voltage measurements and monitoring the appearance of shunts using illuminated lock‐in thermography measurements. Furthermore, to analyze the effect on the final triple–junction solar cell, the triple‐junction device is brought in different current limitation conditions. It is shown that the subcell breakdown can happen during the operation of the triple‐junction solar cell, especially for the case where the perovskite top cell is limiting the overall current of the device. This effect is less severe when the middle perovskite cell limits the current due to the absence of a direct contact with the silver metallization which has shown to be the major degradation site during reverse biasing of perovskite solar cells. Finally, there is no concern regarding breakdown of the silicon bottom cell due to the higher breakdown voltage of silicon compared to perovskite.

A Double Compatibilization Strategy To Boost the Performance of p-i-n Solar Cells Based on Perovskite Deposited in Humid Ambient Air.

Formamidinium lead iodide (FAPI) represents the most promising perovskite for single junction solar cells, exhibiting an impressive performance when deposited in a controlled nitrogen environment. In order to foster the real-world application of this technology, the deposition of FAPI in ambient air is a highly desirable prospect, as it would reduce fabrication costs. This study demonstrates that the wettability of FAPI precursors on the hole transporting layers (HTL) used to fabricate inverted p-i-n solar cells is extremely poor in ambient air, hampering the realization of a perovskite active layer with good optoelectronic quality. To address this issue, herein, a double compatibilization method is developed, which results in the attainment of remarkable performance, exceeding 21%, representing one of the highest reported efficiencies for FAPI solar cells fabricated in humid ambient air. The incorporation of a small quantity of anionic surfactant, comprising a hydrocarbon tail and a polar headgroup, sodium dodecyl sulfate (SDS), in the perovskite solution and an ultrathin layer of alumina nanoparticles on the HTL, results in a significant improvement in the wettability of the FAPI solution. This enables the reproducible deposition of highly homogeneous perovskite films with complete coverage and excellent optical and optoelectronic quality. Furthermore, devices based on FAPI with SDS exhibit enhanced stability, retaining 98% of their initial efficiency after 40 h of continuous illumination.

Carrier transport layer engineering of Cs2TiI2Br4 halide double perovskite solar cell via SCAPS 1D: Approaching the Shockley-Queisser limit

All-inorganic Cs2TiIxBr(6-x)-based perovskite solar cells (PSCs) are recently attracting a lot of attention for their tunable bandgaps, earth abundance, non-toxicity, and ultra-stability. Among the Cs2TiIxBr(6-x) family of materials, Cs2TiI2Br4 with a bandgap of ∼1.38 eV has the potential to be an excellent single junction solar cell material with a theoretically higher Shockley-Queisser limit of power conversion efficiency (PCE). Its excellent optoelectronic properties make it a potential candidate for being the highest-performing PSC from the Cs2TiIxBr(6-x) family. In our study, a total of eight hole transport materials (P3HT, PTAA, Spiro-OMeTAD, PEDOT:Pss, CuSCN, CuI, NiO, and MoO3) and six electron transport materials (PCBM, TiO2, CdS, SnO2, ZnO, and IGZO) were investigated to select suitable charge transport materials. The defect densities of interface and absorber, different absorber layer thicknesses, several metal work functions, series-shunt resistance, and temperature were investigated to derive the conditions for optimum performance. After thorough investigation, we derived four novel devices with the combination of all the organic and inorganic charge transport materials to provide optimum performance. Among them, the combination of inorganic SnO2 and CuSCN as electron and hole transport layer respectively achieved the highest PCE of 23.41 %.

23.6 % Efficient perovskite-organic tandem photovoltaics enabled by recombination layer engineering

Recombination layers are crucial in achieving high power conversion efficiency (PCE) in tandem solar cells. Here, we report the development and optimization of recombination junctions for high PCE perovskite-organic tandem solar cells (PO-TSCs). We choose a wide bandgap perovskite (1.79 eV) for the front subcell and a narrow bandgap (1.36 eV) organic bulk heterojunction (BHJ) for the rear subcell. The optimal thicknesses of the perovskite and organic layers were determined to be 260 and 100 nm, respectively, based on the analysis of Transfer-Matrix optical simulations. Our results demonstrate that the optimal recombination layer consists of an ultrathin layer of indium zinc oxide IZO (∼ 2 nm) deposited on MoOx/2PACz, which delivers a PCE of 23.6 %. This high PCE is attributed to the high transparency of the recombination layer in the NIR spectra region and the low sheet resistance of IZO. Furthermore, we provide a theoretical analysis of the potential efficiency of PO-TSCs as a function of front and rear subcells and predict a maximum theoretical PCE value of more than 36 %. Our work highlights the importance of selecting the proper recombination layer design for achieving high-performance PO-TSCs.

Thermoelectric and photovoltaic properties of 12-BaBi2S4

In this report, we have investigated the structure and properties of the 12-BaBi2S4. A single crystal X-ray diffraction study shows that the 12-BaBi2S4 crystallizes in the hexagonal crystal system (space group = P63/m) with refined lattice parameters of a = b = 25.2687(10) Å, c = 4.1859(2) Å, and formula unit = Z = 12 at room temperature. The structure contains fifteen crystallographic independent sites, including three Ba, four Bi, and eight types of S atoms. A phase pure polycrystalline sample of 12-BaBi2S4 was synthesized by heating stoichiometric amounts of BaCO3 and Bi2O3 under a CS2 atmosphere. The phase pure sample is found to be a semiconductor with a direct bandgap of 1.3(1) eV. The polycrystalline 12-BaBi2S4 exhibits ultra-low thermal conductivity values, varying from 0.47 Wm−1K−1 at 323 K to 0.43 Wm−1K−1 at 773 K. The sample shows high values of the Seebeck coefficient (S = −300 μV/K to −210 μV/K) in the 323 K–773 K range with poor electrical conductivity values. The negative sign of the S implies that the sample is a n-type semiconductor. DFT studies of the 12-BaBi2S4 also predict semiconducting properties. We have explored the 12-BaBi2S4 sample for photovoltaic (PV) applications by fabricating a liquid junction solar cell, TiO2/CdS/12-BaBi2S4/Sn2−/S2−/MWCNTs@Ni, which delivered an efficiency enhanced by ∼12 % to the control cell based on sole CdS as the photo-sensitizer. Theoretical electronic structure calculations suggest the semiconducting nature of the 12-BaBi2S4 in agreement with the optical absorption and electrical resistivity studies.

Maximal Efficiencies in GaP_(1-x) 〖Te〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

In n^+ (p^+)-p(n) [X(x)≡GaP_(1-x) Te_x]-alloy junction solar cells at T=300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent works [1, 2], we will also investigate the maximal efficiencies, η_(Imax.(IImax.)), obtained at the open circuit voltage V_oc (=V_(ocI(ocII))), according to highest hot reservoir temperatures, T_H (K), obtained from the Carnot efficiency theorem, which was demonstrated by the use of the entropy law. In the present work, some concluding remarks are given in the following.(1) In the heavily doped emitter region, the effective density of electrons (holes), N^*, given in parabolic conduction (valence) bands, expressed as functions of the total dense impurity density, N, donor (acceptor)-radius, r_(d(a)), and x-concentration, is defined in Eq. (9d), as: N^* 〖(N,r〗_(d(a)),x)〖≡N-N〗_CDn(NDp) 〖(r〗_(d(a)),x), where N_CDn(NDp) is the Mott critical density in the metal-insulator transition, determined in Eq. (9a). Then, we have showed that (i) the origin of such the Mott’s criterium, Eq. (9a), is exactly obtained from the reduced effective Wigner-Seitz radius r_(sn(sp)), characteristic of interactions, as given in Equations (9b, 9c), and further (ii) N_(CDn(CDp)) is just the density of electrons (holes) localized in the exponential conduction (valence)-band tail (EBT), as that demonstrated in [1].(2) In Table 3n, for the n^+-p GaP_(1-x) Te_x-alloy junction solar cell and for r_(Sn(Cd))-radius, one obtains with increasing x=(0, 0.5, 1): η_(Imax.) (↘)= 32.83 %, 32.82 %, 32.79 %, according to T_H (↘)=446.6 K,446.5 K,446.3 K, at V_ocI=1.06 V,1.06 V,1.06 V, respectively.(3) In Table 5p, for the p^+-n GaP_(1-x) Te_x-alloy junction solar cell and for r_(Cd(Sn))-radius, one obtains with increasing x=(0, 0.5, 1): η_(IImax.) (↘)= 32.41 %, 32.39 %, 32.37 %, according to T_H (↘)=443.8 K,443.7 K,443.6 K, at V_ocII (V)[>V_ocI (V)]=1.17 V,1.17 V,1.17 V, respectively, suggesting that such η_(Imax.(IImax.))-and-T_H variations depend on V_ocII (V)[>V_ocI (V)]-ones.

Maximal Efficiencies in GaP_(1-x) 〖Sb〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

In n^+ (p^+)-p(n) [X(x)≡GaP_(1-x) Sb_x]-alloy junction solar cells at T=300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent works [1, 2], we will also investigate the maximal efficiencies, η_(Imax.(IImax.)), obtained at the open circuit voltage V_oc (=V_(ocI(ocII))), according to highest hot reservoir temperatures, T_H (K), obtained from the Carnot efficiency theorem, which was demonstrated by the use of the entropy law. In the present work, some concluding remarks are given in the following.(1) In the heavily doped emitter region, the effective density of electrons (holes), N^*, given in parabolic conduction (valence) bands, expressed as functions of the total dense impurity density, N, donor (acceptor)-radius, r_(d(a)), and x-concentration, is defined in Eq. (9d), as: N^* 〖(N,r〗_(d(a)),x)〖≡N-N〗_CDn(NDp) 〖(r〗_(d(a)),x), where N_CDn(NDp) is the Mott critical density in the metal-insulator transition, determined in Eq. (9a). Then, we have showed that (i) the origin of such the Mott’s criterium, Eq. (9a), is exactly obtained from the reduced effective Wigner-Seitz radius r_(sn(sp)), characteristic of interactions, as given in Equations (9b, 9c), and further (ii) N_(CDn(CDp)) is just the density of electrons (holes) localized in the exponential conduction (valence)-band tail (EBT), as that demonstrated in [1]. (2) In Table 3n, for the n^+-p GaP_(1-x) 〖Sb〗_x-alloy junction solar cell and for r_(Sn(Cd))-radius, one obtains with increasing x=(0, 0.5, 1): η_(Imax.) (↘)= 32.83 %, 29.58 %, 23.77 %, according to T_H (↘)=446.6 K,426.0 K,393.5 K, at V_ocI=1.06 V,1.06 V,1.29 V, respectively.(3) In Table 5p, for the p^+-n GaP_(1-x) 〖Sb〗_x-alloy junction solar cell and for r_(Cd(Sn))-radius, one obtains with increasing x=(0, 0.5, 1): η_(IImax.) (↗)= 32.41 %, 34.32 %, 35.19 %, according to T_H (↗)=443.8 K,456.8 K,462.9 K, at V_ocII (V)[>V_ocI (V)]=1.17 V,1.25 V,1.44 V, respectively, suggesting that such η_(Imax.(IImax.))-and-T_H variations depend on V_ocII (V)[>V_ocI (V)]-ones.

Maximal Efficiencies in Ga〖Te〗_(1-x) 〖Sb〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

Maximal Efficiencies in Ga〖Te〗_(1-x) 〖Sb〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

Maximal Efficiencies in Ga〖Te〗_(1-x) P_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

In n^+ (p^+)-p(n) [X(x)≡Ga〖Te〗_(1-x) P_x]-alloy junction solar cells at T=300 K, 0≤x≤1, by basing on the same physical model and the same treatment method, as those used in our recent works [1, 2], we will also investigate the maximal efficiencies, η_(Imax.(IImax.)), obtained at the open circuit voltage V_oc (=V_(ocI(ocII))), according to highest hot reservoir temperatures, T_H (K), obtained from the Carnot efficiency theorem, which was demonstrated by the use of the entropy law. In the present work, some concluding remarks are given in the following.(1) In the heavily doped emitter region, the effective density of electrons (holes), N^*, given in parabolic conduction (valence) bands, expressed as functions of the total dense impurity density, N, donor (acceptor)-radius, r_(d(a)), and x-concentration, is defined in Eq. (9d), as: N^* 〖(N,r〗_(d(a)),x)〖≡N-N〗_CDn(NDp) 〖(r〗_(d(a)),x), where N_CDn(NDp) is the Mott critical density in the metal-insulator transition, determined in Eq. (9a). Then, we have showed that (i) the origin of such the Mott’s criterium, Eq. (9a), is exactly obtained from the reduced effective Wigner-Seitz radius r_(sn(sp)), characteristic of interactions, as given in Equations (9b, 9c), and further (ii) N_(CDn(CDp)) is just the density of electrons (holes) localized in the exponential conduction (valence)-band tail (EBT), as that demonstrated in [1].(2) In Table 3n, for the n^+-p X(x)-alloy junction solar cell and for r_(Sn(Cd))-radius, one obtains with increasing x=(0, 0.5, 1): η_(Imax.) (↗)= 32.70 %, 32.72 %, 32.77 %, according to T_H (↗)=445.8 K,445.9 K,446.2 K, at V_ocI=1.06 V,1.06 V,1.06 V, respectively.(3) In Table 5p, for the p^+-n X(x)-alloy junction solar cell and for r_(Cd(Sn))-radius, one obtains with increasing x=(0, 0.5, 1): η_(IImax.) (↗)= 32.32 %, 32.34 %, 32.35 %, according to T_H (↗)=443.3 K,443.4 K,443.4 K, at V_ocII (V)[>V_ocI (V)]=1.17 V,1.17 V,1.17 V, respectively, suggesting that such η_(Imax.(IImax.))-and-T_H variations depend on V_ocII (V)[>V_ocI (V)]-ones.

Maximal Efficiencies in Ga〖Te〗_(1-x) 〖As〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem

Maximal Efficiencies in Ga〖Te〗_(1-x) 〖As〗_x-Alloy Junction Solar Cells at 300 K, According to Highest Hot Reservoir Temperatures, Obtained from Carnot-Efficiency Theorem