Pristine Si Research Articles

MoS2 synthesis on fluorine-terminated Si substrates prepared by SF6 mixed gas plasma

MoS2 synthesis methods with fewer grain boundaries are expected for device applications. To control the nucleation density and to increase the domain size of MoS2 on a Si substrate, MoS2 was synthesized on a fluorine-terminated Si substrate prepared by SF6 mixed gas plasma. The average domain size of monolayer MoS2 synthesized on a fluorine-terminated Si substrate was several times larger than that on a pristine Si substrate, and grain boundaries were reduced. The MoS2 synthesized on the fluorine-terminated substrate was found to have improved crystallinity based on the results of Raman and photoluminescence spectroscopy. XPS analysis showed that no residual fluoride was observed on the substrate surface after CVD, suggesting that fluorine atoms were volatilized together with Mo by chemical reaction during CVD. Fluorine-terminated surfaces prepared by SF6 mixed gas plasma contribute to increasing the domain size of MoS2, and it can be applied for selective growth in the subsequent CVD synthesis of MoS2.

Stress-Relieving Carboxylated Polythiophene/Single-Walled Carbon Nanotube Conductive Layer for Stable Silicon Microparticle Anodes in Lithium-Ion Batteries.

Stress-relieving and electrically conductive single-walled carbon nanotubes (SWNTs) and conjugated polymer, poly[3-(potassium-4-butanoate)thiophene] (PPBT), wrapped silicon microparticles (Si MPs) have been developed as a composite active material to overcome technical challenges such as intrinsically low electrical conductivity, low initial Coulombic efficiency, and stress-induced fracture due to severe volume changes of Si-based anodes for lithium-ion batteries (LIBs). The PPBT/SWNT protective layer surrounding the surface of the microparticles physically limits volume changes and inhibits continuous solid electrolyte interphase (SEI) layer formation that leads to severe pulverization and capacity loss during cycling, thereby maintaining electrode integrity. PPBT/SWNT-coated Si MP anodes exhibited high initial Coulombic efficiency (85%) and stable capacity retention (0.027% decay per cycle) with a reversible capacity of 1894 mA h g-1 after 300 cycles at a current density of 2 A g-1, 3.3 times higher than pristine Si MP anodes. The stress relaxation and underlying mechanism associated with the incorporation of the PPBT/SWNT layer were interpreted by quasi-deterministic and quantitative stress analyses of SWNTs through in situ Raman spectroscopy. PPBT/SWNT@Si MP anodes can maintain reversible stress recovery and 45% less variation in tensile stress compared with SWNT@Si MP anodes during cycling. The results verify the benefits of stress relaxation via a protective capping layer and present an efficient strategy to achieve long cycle life for Si-based anodes for next-generation LIBs.

Doping-induced spin polarization on the pristine Si surface: a Si(5 5 12)2 × 1 case

Doping-induced spin polarization on the pristine Si surface: a Si(5 5 12)2 × 1 case

Artificial photosynthetic approach steers hydrogen evolution with bismuth selenide nanoflakes decorated silicon nanowires

Photoelectrochemical (PEC) water splitting offers a promising path toward green hydrogen production, but developing efficient photocatalysts remains a critical hurdle for large-scale adoption. In this study, we introduced a novel hybrid heterostructure for PEC water splitting, consisting of bismuth selenide (Bi2Se3) decorated silicon nanowires (Si NWs). This configuration achieved a high current density of 10.3 mA/cm2 at −1.2 V vs. RHE, along with an ABPE of 2.5 % at −0.8 V vs. RHE. Notably, these performance metrics surpass those of pristine Si NWs. The topological surface states in Bi-based layered chalcogenides, Bi2Se3 as cocatalysts with Si NWs, demonstrate robust charge transport which improves the conductivity of photoelectrodes in electrochemical reactions with high stability. Thus, the present study exploits the layered chalcogenides as an excellent cocatalyst for Si NWs that may lead to further advances in the hydrogen evolution reaction.

Engineering Nano-Sized Silicon Anodes with Conductive Networks toward a High Average Coulombic Efficiency of 90.2% via Plasma-Assisted Milling.

Si-based anode is considered one of the ideal anodes for high energy density lithium-ion batteries due to its high theoretical capacity of 4200 mAh g-1. To accelerate the commercial progress of Si material, the multi-issue of extreme volume expansion and low intrinsic electronic conductivity needs to be settled. Herein, a series of nano-sized Si particles with conductive networks are synthesized via the dielectric barrier discharge plasma (DBDP) assisted milling. The p-milling method can effectively refine the particle sizes of pristine Si without destroying its crystal structure, resulting in large Brunauer-Emmett-Teller (BET) values with more active sites for Li+ ions. Due to their unique structure and flexibility, CNTs can be uniformly distributed among the Si particles and the prepared Si electrodes exhibit better structural stability during the continuous lithiation/de-lithiation process. Moreover, the CNT network accelerates the transport of ions and electrons in the Si particles. As a result, the nano-sized Si anodes with CNTs conductive network can deliver an extremely high average initial Coulombic efficiency (ICE) reach of 90.2% with enhanced cyclic property and rate capability. The C-PMSi-50:1 anode presents 615 mAh g-1 after 100 cycles and 979 mAh g-1 under the current density of 5 A g-1. Moreover, the manufactured Si||LiNi0.8Co0.1Mn0.1O2 pouch cell maintains a high ICE of >85%. This work may supply a new insight for designing the nano-sized Si and further promoting its commercial applications.

(Invited) Advanced Photoelectron Spectroscopy on Battery Materials: Lessons Learnt on Silicon- Containing Electrodes

While Silicon (Si) is being incorporated more and more as an active material in commercial lithium-ion batteries, it is still a topic of intense research and the motivation for these research efforts remains unchanged: Silicon’s large volume expansion during cycling leads rapid capacity fading largely associated with changes in the Si surface chemistry and unstable solid electrolyte interphase (SEI). Using advanced photoelectron spectroscopy (PES) characterization, we have investigated crucial interfaces on Si model systems and Si-containing negative electrodes for Li-ion batteries. Here, we focus on two approaches to influence the SEI composition intrinsically: Binders and electrolytes.Starting with pristine Si powders, we studied the effect of carboxylic acids as electrode slurry additives on the Si surface chemistry before and after electrochemical cycling [1] using synchrotron PES depth profiling. Further, we used photoelectron spectroscopy to confirm cross-linking in poly-acrylic acid-based binder for Si electrodes and showed that the cross-linking agent pentaerythritol had no negative effect on the SEI thus attributing improved cycling performance to increased binder cross-linking [2].In silicon/graphite negative electrodes, we used PES to elucidate the influence of fluoroethylene carbonate (FEC) on the degradation phenomena in electrodes with varying silicon content [3]. Finally, photoelectron spectroscopy provided insights into what happens to the SEI on Si-containing electrodes if we replace the classical electrolyte solvent ethylene carbonate with either FEC or glyoxylic acetal-based alternatives [4, 5].[1] F. Jeschull, H.Q. Pham, A. Ghamlouche, P.K. Thakur, S. Trabesinger, J. Maibach, J. Phys. Energy 2023, 5 (2), 025002. https://doi.org/10.1088/2515-7655/acbbee.[2] J. He, C. Das, F. Yang, J. Maibach, Electrochimica Acta 2022, 411, 140038. https://doi.org/10.1016/j.electacta.2022.140038.[3] A. Ghamlouche, M. Müller, F. Jeschull, J. Maibach, J. Electrochem. Soc. 2022. https://doi.org/10.1149/1945-7111/ac4cd3.[4] L. Gehrlein, C. Njel, F. Jeschull, J. Maibach, ACS Appl. Energy Mater. 2022, 5 (9), 10710–10720. https://doi.org/10.1021/acsaem.2c01454.[5] L. Gehrlein, C. Leibing, K. Pfeifer, F. Jeschull, A. Balducci, J. Maibach, Electrochimica Acta 2022, 140642–140642. https://doi.org/10.1016/j.electacta.2022.140642.

Epitaxial growth of Si thin films with hexagonal close-packed structures on metal substrates.

We have studied the epitaxial growth of Si thin films on the Cd(0001) surface using low-temperature scanning tunneling microscopy. When deposited at low temperatures (100K), Si atoms form dendritic islands with triangular shapes, indicating the existence of anisotropic edge diffusion in the process of Si film growth. After annealing to elevated temperatures, the triangular dendritic Si islands become hexagonal compact islands. Moreover, the 2D Si islands located on two different substrate terraces exhibit different heights due to the influence of quantum-well states in Cd(0001) films. Based on high-resolution scanning tunneling microscopy images, it is observed that the first, second, and third Si layers show the pseudomorphic 1 × 1 structure. In particular, the first and second layer islands reveal the opposite triangles, indicating the hexagonal close-packed stacking of Si atoms. These results provide important information for the growth of pristine Si films on metal substrates and the understanding of Si-metal interaction.

Facile construction of nanowires via etching process to increase heterostructure area for efficient photocatalysis

Semiconductor photocatalysts can eliminate organic pollutants completely, but the poor utilization of solar energy and rapid recombination of photogenerated electron-hole pairs have become a vital obstacle for their widespread application. Herein Si/TiO2 nanowire arrays with core–shell structures were fabricated by metal-assisted chemical etching and atomic-layered deposition. The physical properties and photocatalytic performance of the specimens were tested and compared with pristine Si nanowire arrays. The specimens showed perfect light absorption. The photoluminescence was generally depressed by the shell layer, and the photocurrent and photocatalytic efficiency of Si/TiO2 were improved by 297 and 2 times respectively in contrast to Si. The magnitude of the photocurrent and photocatalytic activity could be modulated by the etching period, in which an ideal etching time of 2 h produced the highest photocatalytic performance. The high efficient photocatalysis of the heterostructure was well illustrated by the Z-scheme band alignment and large specific surface area.

Operando Nanomechanical Mapping of Silicon Thin Film Electrode during the First Lithiation and Delithiation Investigated By Bimodal Atomic Force Microscopy

Si is emerging as one of the most prospective anode materials for all-solid-state Li-ion batteries due to its extremely high theoretical capacity density of 4200 mAh g-1 and relatively negative potential for lithiation/delithiation. Towards its widespread use, controlling severe volume expansion/contraction during lithiation/delithiation is a challenge because it may cause cracking, fracture, and pulverization that negatively influence the cycle performance and rate capability of the cells [1]. Such mechanical event is induced by the change in the lattice structure due to the formation of LixSi and successive increasing/decreasing of Li content x in LixSi [2].Bimodal atomic force microscopy (AFM) offers quantitative mapping of nanoscale mechanical property, simultaneously with surface topography imaging [3]. Our group previously applied this technique to the cross-section of a composite electrode consist of active materials, binders, conductive additives, and deposited electrolyte solution and successfully demonstrated nanomechanical mapping [4]. Here, we develop an operando bimodal AFM system to track Young’s modulus changes of electrode materials in an all-solid-state battery configuration during the lithiation and delithiation reactions in real-time.A cell in a Cu/Si/LLZT/In/Li configuration was fabricated as follows; a 3 µm-thick Si thin-film and a 100 nm-thick Cu layer were sputter-deposited on one side of Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte, an In layer was sputter-deposited on the other side of LLZT, the Cu/Si/LLZT/In sample was milled with an Ar-ion beam to yield a flat and smooth cross-section suitable for AFM analysis, and then a 50 µm-thick Li metal foil was combined with the pre-coated In thin layer. Operando nanomechanical mapping was performed by mounting the cross-section-exposed cell in the custom-made sample holder coupled with a potentiostat for bias applications, in an Ar-filled glove box to prevent any atmospheric influences.Electrochemical lithiation and delithiation were carried out within a potential window of 0.01-1.20 V vs. Li/Li+. Electrochemical characterization indicated that the capacities of the Si electrode for the first lithiation and delithiation are 3300 and 1833 mAh g-1, respectively. These capacities are equal to the formation of Li3.46Si after the first lithiation of the pristine Si and Li1.54Si after the successive delithiation from Li3.46Si. Throughout the lithiation, the averaged Young’s modulus of Si electrode decreased due to the formation of LixSi and increase in the Li content x in LixSi. In the initial stage of lithiation, it drastically decreased because LixSi was formed by the lithiation of pristine Si. Then, it moderately decreased with increasing Li content x in LixSi. Unfortunately, the Young’s modulus maps were only recorded until the formation of Li1.54Si because the successive delithiation was not completed possibly due to the phase transformation of crystalline LixSi to amorphous LixSi [5], which may cause a significant mechanical strain inside the thin film. The measured Young’s modulus values were consistent with those obtained by first principle calculation [6]. Further details are given at the presentation.

Three-dimensional angle-resolved photoemission study of bulk SiGe single crystals

The composition- and structure-dependent electronic band structure of SiGe alloys facilitates a rich variety of its application in various fields. In this study, we performed high-resolution core-level and angle-resolved photoemission spectroscopy (ARPES) of unstrained SiGe single crystals with the (001) surface. Thermally cleaned surfaces of the single crystals of SiGe alloys exhibited double domain (2 × 1) reconstruction, wherein the asymmetric dimer was composed of Ge atoms, and Si atoms were located below the subsurface region. The compositional dependence of three valence bands and their constant energy contours were clearly resolved by three-dimensional ARPES measurements using the high-intensity synchrotron radiation. The valence bands of unstrained SiGe alloys could be well described by the composition-based interpolation of the band parameters of pristine Si and Ge crystals.

Proximity Coupling of Graphene to a Submonolayer 2D Magnet.

Imprinting magnetism into graphene may lead to unconventional electron states and enable the design of spin logic devices with low power consumption. The ongoing active development of 2D magnets suggests their coupling with graphene to induce spin-dependent properties via proximity effects. In particular, the recent discovery of submonolayer 2D magnets on surfaces of industrial semiconductors provides an opportunity to magnetize graphene coupled with silicon. Here, synthesis and characterization of large-area graphene/Eu/Si(001) heterostructures combining graphene with a submonolayer magnetic superstructure of Eu on silicon are reported. Eu intercalation at the interface of the graphene/Si(001) system results in a Eu superstructure different from those formed on pristine Si in terms of symmetry. The resulting system graphene/Eu/Si(001) exhibits 2D magnetism with the transition temperature controlled by low magnetic fields. Negative magnetoresistance and the anomalous Hall effect in the graphene layer provide evidence for spin polarization of the carriers. Most importantly, the graphene/Eu/Si system seeds a class of graphene heterostructures based on submonolayer magnets aiming at applications in graphene spintronics.

Recent advancements in hydrogen storage - Comparative review on methods, operating conditions and challenges

Green hydrogen, proposed as a sustainable alternative for conventional fuels, has gained utmost importance due to its reduced carbon footprint and potential application in maintaining balance between energy generation and demand. Utilization of hydrogen-based systems are challenged by cost effective storage methods. Bio-hydrogen storage technologies using cryogenic and adsorptive methods are discussed in this review paper, along with their operating conditions and storage capacities. An analysis of operational challenges and recent advancements in hydrogen storage techniques is presented. With a storage pressure of 70 MP, cryogenic hydrogen is almost twice as dense as compressed hydrogen. Technical challenges such as material cost and explosion risk can be addressed by hydrogen adsorption on activated carbon active sites. Maximum hydrogen storage capacity are reported by activated carbon obtained from Chitosan (6.77 wt%), Bamboo (6.6 wt%) and African palm shell (6.5 wt%) at 77 K and 4–20 Mpa. Further, nanotechnology approaches are presented in detail for increasing hydrogen storage capacity in pristine Si and Mg. The future perspectives in terms of technological, and economic aspects are discussed.

Numerical simulation on the impurity photovoltaic (IPV) effect in c-Si wafer-based dual-heterojunction solar cell

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 cell 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 44.47%, with a J SC = 48.95 mA/cm 2 , V OC = 1.063 V and FF= 85.46%, 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. • IPV effect in an n + -p-p + Si DH solar cell with Tl impurity has been simulated. • ZnSe and AlSb have been used as window and BSF layers, respectively. • The optimized metal contacts Ti (cathode) and Ni (anode) has been established. • A maximum J SC of 48.95 mA/cm 2 and PCE= 44.47% with V OC = 1.063 V has been achieved. • n + - ZnSe /p- Si /p + - AlSb DH solar cell with Tl impurity shows potential in future.

Eu3+ doped CsPbCl2Br1 nanocrystals glass for enhanced the ultraviolet response of Si photodetectors

Silicon (Si) photodetectors (PDs) have been widely used due to their many excellent properties, however, the extremely weak ultraviolet (UV) photo-response severely affect its future development. In this work, we controlled the concentration of CsPbCl2Br1 NCs in the glass and obtained samples with local emission and high transmittance. Furthermore, we incorporated Eu3+ into CsPbCl2Br1 perovskite nanocrystals glass (PNG) to achieve efficient ultraviolet (UV) to visible emissions and boost the UV response of Si PDs. Finally, after combining with the CsPbCl2Br1: Eu3+ PNG on the Si PDs, the responsivity increased to 0.0088 A/W at 320 nm, which means 8.8 times higher than that of the pristine Si PDs. Moreover, Si PDs based on CsPbCl2Br1: Eu3+ PNG exhibited excellent stability, and the photocurrents of the device almost not changed after 60 days. This work offers a novel strategy for improving UV response of Si PDs.

Double-shell interphase design enabling suppressed side reactions for stable Si battery anode

Silicon (Si)-based anode is promising for the next-generation high-energy lithium-ion batteries due to the high capacity. However, it suffers parasitic side reactions between electrode and electrolyte in the initial cycle, which consumes abundant active lithium and makes it one of the limiting factors for the implementation of Si-based anodes. It is of vital importance to suppress the side reactions at the electrode interphase and improve the electrochemical/chemical stability. Here, we designed an ultrathin double-shell interphase structure (∼15 nm), consisting of an inner VO2 nanoshell and an outer C nanoshell. The inner VO2 nanolayer avoided the direct contact between active Si and electrolyte, and, thus, hindered the side reactions between them. The carbon nanolayer stabilized the VO2 layer mechanically and improved the electronic conductivity of the anode materials. Thus, a thin solid electrolyte interphase was formed on the as-designed Si@VO2@C surface, and high initial Coulombic efficiency (ICE) was realized. Notably, the Si@VO2@C electrode exhibited a high reversible capacity of 2300 mAh g−1 at 0.1 C and high ICE of 90.2%, which was about 18% higher than that of a pristine Si electrode. Also, the electrode displayed stable electrochemical cycling with high capacity retention of 84.8% for 100 cycles at 0.4 C. With 15 wt. % addition into the graphite, the hybrid electrode Si@VO2@C/graphite exhibited a high reversible charge capacity of 596 mAh g−1 and satisfactory cycling performance with high capacity retention of 83.8% at 100 mA g−1 under a high area capacity of 3.46 mAh cm−2, showing promise for the practical application.

Facile co-electrodeposition of amorphous silicon anode with embedded nickel nanoparticles for enhancing rate capability in lithium-ion batteries

• Potentiostatic co-electrodeposition enables incorporation of Ni nanoparticles into Si matrix. • Crystalline Ni nanoparticles enhances total electrical conductivity of Si anode. • Ni particles effectively buffers the volume change of Si matrix during charge/discharge. • A high discharge capacity of 1633 mA h g −1 is retained after 100 charge-discharge cycles. Many efforts have been invested to improve the electrical conductivity and stability of Si anode, such as alloying and adding conductive additives, which unfortunately, are difficult for large scale manufacturing due to the complicated and expensive preparation techniques. In this work, a Si–Ni composite anode is prepared by a facile potentiostatic co-electrodeposition approach from organic solution. Correspondingly, it exhibits a capacity as high as 1633 mA h g − 1 after 100 charge-discharge cycles, whereas, Si–Ni composite anodes synthetized by previous approaches show specific capacity less than 1200 mA h g − 1 . It is believed that Ni nanoparticles with a diameter from 3 to 10 nm embedded in amorphous Si not only result in a lower resistance of Si–Ni anode compared with pristine Si anode, thus enhancing the rate performance, but also stabilize the integrity of the amorphous Si matrix, and buffer the volume change of Si anode during the lithiation–delithiation processes, thus improving the cycling performance.

Propelling performance of silicon thin film lithium ion battery by appropriate dopants

Although pristine silicon (Si) has been employed as a high-capacity anode material, high performance of Si-based lithium-ion battery (LIB) still remains challenging constrained mainly by low intrinsic electrical conductivity of the semiconductor. This drawback can be addressed by doping Si with group III and V elements; nevertheless, a systematic study on the doping species is rarely reported. Herein, the effects of dopants (boron and arsenic) in Si thin film anodes, prepared by electron beam evaporation from different target materials (including pristine, p-type, and n-type Si), on the performance of LIB are investigated. In a coin cell configuration, the doped Si films are inferior to the pristine counterparts in terms of irreversible capacity loss at the first circle, possibly due to incorporation of more lithium ions with a higher conductivity in the former. Intriguingly, boron and arsenic ions are demonstrated as regulating dopants that can deteriorate (for the former) or enhance (for the latter) the capacity retention and rate capabilities of the pristine Si-based LIBs. Electrochemical impedance spectroscopy and microstructure characterizations reveal that the high electrical conductivity and chemical reactivity of boron ions with electrolytes aggravate the formation and propagation of cracks into the depth during cycling and thicken the thickness of solid electrode interphase, consequently increasing charge transfer impedance. This study clarifies the working mechanisms of different doping species in the Si thin film anodes in response to electrochemical cycling and shed light on the improved performance of thin film based LIBs with appropriate dopants.

Enhanced thermoelectric performance of vertically aligned silicon nanowires through the cold spot effect and charge carrier trapping effect of attached gold nanoparticles

The thermoelectric performance of vertically aligned silicon (Si) nanowires (NWs) with diameters of 100–150 nm fabricated through metal-assisted chemical etching is improved using electroless-deposited gold (Au) nanoparticles (NPs) (ф ≈ 10 nm). After the deposition of metal NPs, the thermal conductivity and Seebeck coefficient of the Si NWs decrease 5.78-fold and increased 2.71-fold, respectively. Despite the 3.23-fold increase in the electric resistivity of Si NWs through the deposition of Au NPs, the figure of merit of the Au NP-deposited Si NWs is enhanced by 1320% (0.444) compared to that of pristine Si NWs (0.0337). The power factor is enhanced 2.28-fold after Au NP deposition (0.175–0.400 mV·K−2m−1). Based on finite-element method simulations of Au NP-deposited Si NW, a cold spot is generated inside the Si NW by the attached Au NP. Moreover, charge carrier trapping at the interface between the Si NW and Au NP is anticipated due to interfacial Fermi-level pinning. Cold spot and charge carrier trapping effects are proposed as important factors for enhancing the thermoelectric performance of Au NP-deposited Si NWs.

Enhancing role of structurally integrated V2C MXene nanosheets on silicon anode for lithium storage

High-energy lithium-ion batteries (LIBs) have been actively pursued for practical applications in advanced electric vehicles and large-scale energy storage systems. The silicon (Si) material has been considered as a promising anode candidate due to its impressive lithium storage capacity, but is facing the challenge to ameliorate its cycling and rate performance. We here report a structure integration strategy to overcome major issues of poor capacity retention and slow kinetics during the lithium storage of Si anode, through in situ embedding Si nanoparticles into V2C MXene nanosheets. The MXene-supported Si@V2C nanocomposite anode reveals significantly enhanced cycling stability and improved lithium storage kinetics compared to that of the pristine Si anode. A high capacity exceeding to 430 mAh g−1 can be retained for 150 cycles at 200 mA g−1 current density. In addition, the conductive MXene supporter has been demonstrated to facilitate lithiation/delithiation processes for the Si by enhancing the charge transfer kinetics, as it is demonstrated by in situ electrochemical impedance spectroscopic (EIS) and Galvanostatic Intermittent Titration Technique (GITT) measurements. Findings from this work may inspire feasible structural designs for the practical deployment of MXene composited Si anode materials for next-generation lithium-ion batteries.

Theoretical insight into the enhancement of longer-wavelength light absorption in silicon solar cell with multilevel impurities

In this article, we theoretically demonstrate multilevel impurity photovoltaic effect in an efficient silicon dual-homojunction solar cell that ensures an extended absorption of longer wavelength light. Along with suitable contact work functions (Ni and Ta as anode and cathode, respectively), three impurity energy levels from acceptor type impurities (One from Tl and two from Zn) have been introduced in the energy gap of the absorber layer of the solar cell. The simulations have been performed with Solar Cell Capacitance Simulator (SCAPS-1D) program. The pristine Si solar cell shows a PCE of 25.4% with JSC = 37.99 mA/cm2, VOC = 0.780 V and FF = 85.76%. While the incorporation of Tl impurity level alone provides a PCE of 33.4%, with JSC = 51.56 mA/cm2, VOC = 0.789 V and FF = 82.03%, respectively. The PCE of the solar cell further enhances to 35.4% with an elevation of the short circuit current by 3.76 mA/cm2 due to the inclusion of Zn impurity into the optimized structure. This increment of the JSC and hence PCE is evolved from the longer wavelength light absorption due to impurity-assisted two-step photon upconversion in the solar cell.