Carrier Selectivity Research Articles

Process development and integration of double-side Poly-Si passivated solar cells with printed contacts via LPCVD and ex-situ tube diffusion

Tunnel oxide passivated contact (TOPCon) solar cells incorporate doped polycrystalline silicon (poly-Si) thin films to promote charge carrier selectivity and supress recombination, and thus enable very high efficiency. So far, most of TOPCon cells only adopt poly-Si at rear side applications due to its absorptive natures. In this work, we have developed suitable n+ and p+ poly-Si layers via low pressure chemical vapor deposition (LPCVD) and tube diffusion for ex-situ doping. With proper process integration, the fabricated double-side poly-Si solar cells consist of ~20 nm n+ poly-Si grown at front textured surface and ~150 nm p+ poly-Si at rear planar surface. An excellent implied open-circuit voltage (iVoc) of 725 mV with a total J0 value of 16.3 fA/cm2 were obtained on cell precursors capped and hydrogenated by SiNx. We also demonstrated solar cell fabrication and metallisation via industry-viable screen printing, which eliminates the use of transparent conductive oxide (TCO). The phosphosilicate glass (PSG) is found as the key point that determines the firing stabilities. The champion cell implemented with fire-through contacts shows a proof-of-concept efficiency of 19.6% over an area of 196 cm2, which is comparable with the reference cell metallised with the help of a tin-doped indium oxide (ITO) layer.

Effect of Thermal Annealing on the Charge Carrier Selectivity of Ultra‐Thin Organic Interface Dipoles in Silicon Organic Heterojunction Solar Cells

Interfacial layers consisting of organic molecules with a permanent dipole moment exhibit enhanced charge carrier selectivity when applied as electron‐selective contacts in crystalline silicon (c‐Si) heterojunction solar cells. It is found that thermal annealing has a detrimental effect on the charge carrier selectivity of dipole materials based on the amino acid l‐histidine mixed with a fluorosurfactant. Although, the implied open‐circuit voltage (iVoc) increases with annealing, the Voc decreases significantly which is accompanied by a decrease in the built‐in voltage (Vbi) and increase in the specific contact resistivity (ρc). Based on numerical device simulations, it is concluded that the tunneling of electrons through the dipole layer becomes less effective with increasing annealing temperature due to the decomposition of the dipole materials. The decomposition leads to a more “resistive” interfacial layer and to a gradient in the electron quasi‐Fermi potential and, thus, a decrease in Voc. Furthermore, storage under ambient air at room temperature degraded the electron‐selective contacts substantially, limiting the potential of the dipole material for the application in silicon organic heterojunction solar cells.

Impact of Pregrown SiOx on the Carrier Selectivity and Thermal Stability of Molybdenum-Oxide-Passivated Contact for Si Solar Cells.

Thin SiOx interlayers are often formed naturally during the deposition of transition metal oxides on silicon surfaces due to interfacial reaction. The SiOx layer, often only several atomic layers thick, becomes the interface between the Si and deposited metal oxide and can therefore influence the electrical properties and thermal stability of the deposited stack. This work explores the potential benefits of controlling the properties of the SiOx interlayer by the introduction of pregrown high-quality SiOx which also inhibits the formation of low-quality SiOx from the metal-oxide deposition process. This work demonstrates that a high-quality pregrown SiOx can reduce the interfacial reaction and results in a more stoichiometric MoOx with improved surface passivation and thermal stability linked to its lower Dit. Detailed experimental data on carrier selectivity, carrier transport efficiency, annealing stability up to 250 °C, and in-depth material analysis are presented.

Interfacial Engineering of Cu2O Passivating Contact for Efficient Crystalline Silicon Solar Cells with an Al2O3 Passivation Layer

Passivating contacts that simultaneously promote carrier selectivity and suppress surface recombination are considered as a promising trend in the crystalline silicon (c-Si) photovoltaic industry. In this work, efficient p-type c-Si (p-Si) solar cells with cuprous oxide (Cu2O) hole-selective contacts are demonstrated. The direct p-Si/Cu2O contact leads to a substoichiometric SiOx interlayer and diffusion of Cu into the silicon substrate, which would generate a deep-level impurity behaving as carrier recombination centers. An Al2O3 layer is subsequently employed at the p-Si/Cu2O interface, which not only serves as a passivating and tunneling layer but also suppresses the redox reaction and Cu diffusion at the Si/Cu2O interface. In conjunction with the high work function of Au and the superior optical property of Ag, a power conversion efficiency up to 19.71% is achieved with a p-Si/Al2O3/Cu2O/Au/Ag rear contact. This work provides a strategy for reducing interfacial defects and lowering energy barrier height in passivating contact solar cells.

Thermally stable MoOx hole selective contact with Al2O3 interlayer for industrial size silicon solar cells

So far, intrinsic hydrogenated amorphous silicon (a-Si:H(i)) has been commonly used below molybdenum oxide (MoO x ) to form a good contact. An a-Si:H(i)/MoO x stack gives good surface passivation, but often results in poor carrier selectivity after exposure to slightly elevated temperatures >130 °C (Geissbühler et al., 2015) [1]. For this reason, we have investigated an alternative interface layer, a very thin Al 2 O 3 tunneling layer (<2 nm), deposited by atomic layer deposition (ALD), that can provide surface passivation, higher transparency and thermal stability without affecting the hole transport across the contact. To demonstrate this new passivating contact a 6” moly-poly cell, with an Al 2 O 3 /MoO x stack at the front side and n -type doped polysilicon at the rear side, was made using a high- throughput spatial ALD tool, and E-beam PVD, for the Al 2 O 3 and MoO x layers, respectively. This resulted in an efficiency of 18.2% with a V oc of 651 mV, a FF of 75.6% and a J sc of 36.9 mA/cm 2 . A post-deposition anneal (PDA) of the thin Al 2 O 3 interlayer has significant effect on the Al 2 O 3 thickness, layer stoichiometry, contact selectivity, and sputtering-induced damage. Annealing at higher T PDA (350–600 °C) results in ineffective hole carrier transport and makes the stack more sensitive to ITO damage. The best performing device was, therefore, made using an Al 2 O 3 layer without a PDA treatment. Moreover, we have found that this solar cell structure is thermally stable up to at least 210 °C, and even slightly improves under annealing which makes this device industrially appealing. • Thermally stable MoO x selective contact combined with a tunneling AlO x interlayer. • The ALD AlO x interlayer provides surface passivation and effective hole transport. • Efficiency of 18.2% achieved on a 6″ solar cell with improved J sc compared to SHJ. • Carrier-selectivity loss and sputtering damage is prompted by AlO x PDA treatment.

Cerous Fluoride Dopant‐Free Electron‐Selective Contact for Crystalline Silicon Solar Cells

Dopant‐free carrier‐selective contacts have drawn intensive attention for efficient crystalline silicon (c‐Si) photovoltaics due to the low‐temperature simple process and better carrier selectivity. By incorporating a thermally evaporated dielectric film cerium fluoride (CeF3) as the electron transport layer (ETL) between a c‐Si(n) and aluminum (Al) electrode, higher conversion efficiency of the crystalline silicon solar cell is obtained, which is 21.27% compared to 16.89% of a reference cell without CeF3. The insertion of an ultrathin CeF3 ETL helps in alleviating the strong Fermi‐level pinning at the interface, leading to better electron transport with a low contact resistivity of 10.96 mΩ cm2. The morphology and element distribution of the interface are also investigated by high‐resolution transmission electron microscopy (HRTEM). The primary results demonstrate that the utilization of kinds of lanthanide fluorides, including CeF3, offers a good choice for efficient and cost‐effective electron‐selective contacts for optical–electrical devices.

High-Performance p-n Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoOx Doping and Passivation.

Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage (VOC) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoOx (x ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS2) Schottky-junction solar cells with initially near-zero VOC. Doping and passivation turn these into lateral p-n junction photovoltaic cells with a record VOC of 681 mV under AM 1.5G illumination, the highest among all p-n junction TMD solar cells with a practical design. The enhanced VOC also leads to record PCE in ultrathin (<90 nm) WS2 photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.

Approaching 23% silicon heterojunction solar cells with dual-functional SiOx/MoS2 quantum dots interface layers

Silicon heterojunction solar cells based on transition metal oxide carrier-selective contact layers have great potential to achieve high efficiency and low cost. Such system exhibits much lower conversion efficiency compared to the theoretically predicted value. This is mainly due to the difficulty in simultaneously obtaining surface passivation and carrier selectivity at the heterojunction interface. Here we developed a dual-functional SiOx/MoS2 quantum dots hybrid material by ALD in situ growth. The silicon surface is passivated by ultra-thin SiOx layer while the band gap of MoS2 is widen associated with the quantum confinement effect (>3.0 eV for quantum dots). The impurity level is introduced through Mo–O defect engineering, which facilitates carrier selectivity by trap-assisted tunneling. The hybrid materials enabled improved silicon heterojunction solar cells performance with a PCE up to 22.8%. Our advanced interface engineering not only presented a low-cost, high efficiency technical scheme, but also provided guidelines for the design of new low-dimensional hybrid system.

Investigation of the selectivity-mechanism of copper (I) sulfide (Cu2S) as a dopant-free carrier selective contact for silicon solar cells

Carrier selective contacts based on dopant free materials are receiving increased attention. Copper(I) sulfide (Cu2S), earth-abundant and non-toxic, shows potential for use in silicon (Si) solar cells, though its carrier selectivity mechanism remains unclear. We present a detailed investigation of the selectivity mechanisms behind thermally evaporated Cu2S on Si. Deposited Cu2S layers are studied by X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction and UV/VIS (ultraviolet–visible) methods. From X-ray photoelectron spectroscopy and Auger electron spectroscopy, only sulfur related Cu(I) bonds are observed in the deposited film. X-ray diffraction measurements indicate that Cu1.95S (djurleite) may also exist in the film. The indirect and direct bandgaps are determined to be 1.2 eV and 2.2 eV, respectively. Band bending of ~0.6 eV is calculated for Cu2S/n-Si (~5 Ω·cm), while it is significantly lower (~0.07 eV) for Cu2S/p-Si (~2.25 Ω·cm). Current-voltage measurements indicate that the carrier selectivity originates from an induced junction at the Cu2S/n-Si interface, and not from a large band-offset of the conduction band. The Cu2S/p-Si structure displays no carrier selectivity, a finding attributed to the insufficient band bending at the interface.

Design Principles for Efficient and Stable Water Splitting Photoelectrocatalysts

ConspectusPhotoelectrochemical water splitting is a promising avenue for sustainable production of hydrogen used in the chemical industry and hydrogen fuel cells. The basic components of most photoelectrochemical water splitting systems are semiconductor light absorbers coupled to electrocatalysts, which perform the desired chemical reactions. A critical challenge for the design of these systems is the lack of stability for the majority of desired semiconductors under operating water splitting conditions. One strategy to address this issue is to protect the semiconductor by covering it with a stabilizing insulator layer, creating a metal-insulator-semiconductor (MIS) architecture, which has demonstrated improved stability. In addition to enhanced stability, the insulator layer may significantly affect the electron and hole transfer, which governs the recombination rates. Furthermore, the insertion of an insulator layer leads to the introduction of additional insulator/electrocatalyst and insulator/semiconductor interfaces. These interfaces can impact the system's performance significantly, and they need to be carefully engineered to optimize the efficiencies of MIS systems. In this Account, we describe our recent progress in shedding light on the critical role of the insulator and the interfaces on the performance of MIS systems. We discuss our findings by focusing on the concrete example of planar n-type Si protected by a HfO2 insulator layer and coupled to a Ni or Ir electrocatalyst that performs the oxygen evolution reaction, one of the water splitting half-reactions. To improve our fundamental understanding of the insulator layer, we precisely control the HfO2 insulator thickness using atomic layer deposition (ALD), and we perform a series of rigorous electrochemical experiments coupled with theory and modeling. We demonstrate that by tuning the insulator thickness, we can control the flux and recombination of photogenerated electrons and holes to optimize the generated photovoltage. Despite optimizing the thickness, we find that the maximum generated photovoltage in MIS systems is often significantly lower than the upper performance limit, i.e., there are additional losses in the system that could not be addressed by optimizing the insulator thickness. We identify the sources of these losses and describe strategies to minimize them by a combination of improving the semiconductor light absorption, removing nonidealities associated with interfacial defects, and finding alternative insulators with improved charge carrier selectivity. Finally, we quantify the improvements that can be obtained by implementing these specific strategies. Our collective work outlines strategies to analyze MIS systems, identify the sources of efficiency losses, and optimize the design to approach the fundamental performance limits. These general approaches are broadly applicable to photoelectrochemical materials that utilize sunlight to produce value-added chemicals.

Improving passivation properties using a nano-crystalline silicon oxide layer for high-efficiency TOPCon cells

High conversion efficiency can achieve by superior surface passivation and material quality. In this study, a novel passivation contact structure based on nanocrystalline silicon oxide (nc-SiOx) films was investigated. Traditionally, poly silicon junctions in tunnel oxide passivated contact (TOPCon) solar cells possess exceptional junction characteristics, but current losses are noted due to their optical absorption if they are applied in solar cell devices. In this study, we replaced the poly-Si layer in TOPCon solar cells with nc-SiOx to enhance transparency. By employing the nc-SiOx layer, effective surface passivation, carrier selectivity, electrical properties and optical transmission can be used to improve, all are vitally important in devise operation. We optimized the deposited nc-SiOx layer on an ultra-thin (~1.5 nm) silicon dioxide (SiO2) tunnel oxide layer to improve recombination current density and carrier lifetime. The passivation characteristics were improved by varying the annealing temperature and thickness of the nc-SiOx layer. The 50 nm thick nc-SiOx layer was capable of yielding a high implied open-circuit voltage (i-Voc) of 739 mV and low contact resistivity (ρ) of 14.2 (mΩ/cm2) in addition to a low depleted recombination current density (Jo) of 1.1 fA/cm2 with a post-deposition annealing temperature up to 950 °C. Improved passivation characteristics are the result of a more prominent annealing temperature. Our proposed technique has immense potential for achieving higher efficiency for fabricating various structures of TOPCon solar cells. As per AFORST Het simulation results by using nc-SiOx for TOPCon structure, we got Voc of 761.5 mV, Jsc of 43.5 mA/cm2, FF of 83%, and η of 27.49%, respectively.

Electrical Analysis and Comparison of Ta2O5 Tunneling Oxide with SiO2 in Passivated c-Si Solar Cell

The Tantalum oxide material (Ta2O5) as tunnel oxide in comparison with the Silicon dioxide (SiO2) Tunnel oxide is proposed. The lower bandgap and high refractive index of Ta2O5 has several advantages over SiO2. The Ta2O5 is used as Anti-Reflecting coating earlier, but also has capability to behave as the tunneling oxide. In the ultrathin region, the Tantalum oxide (Ta2O5) potentially produces extremely high tunneling and high electric field. The greater electrical intensity increases both the transportation of carrier and passivation quality of designed c-Si structure. The carrier selectivity is also increased due to very high capacitive nature. The performance measurement is done in ASTM certified AM1.5G environment using Silvaco ATLAS 2D TCAD tool. The comparison has been made between Ta2O5 and SiO2, to show the advantage of Ta2O5 over SiO2. The lower bandgap of 4.8eV and higher affinity of 3.19 of Ta2O5 as compared to SiO2 proves to be better material as tunneling oxide. The bandgap and electric field region of both the materials have been studied. In first approach to use Ta2O5 as tunneling oxide, the power conversion 28.42% is obtained for 0.1nm thickness of the Ta2O5. External and internal quantum efficiencies are well above 80% and 90% respectively. The characteristics of the Ta2O5 tunneling based solar cell are compared with the previous reported solar cell.

A Comprehensive Fundamental Understanding of Atomic Layer Deposited Titanium Oxide Films for c-Si Solar Cell Applications

Titanium oxide (TiO x ) film shows excellent surface passivation of crystalline silicon (c-Si) as well as carrier selectivity. The coexistence of both these properties along with extraordinary optical properties of TiO x opens new opportunities to design novel high-performance c-Si solar cells. However, many inconsistent findings have also been reported in the literature that limit the application of TiO x . A greater fundamental insight into TiO x films therefore needs to be developed in order to produce very high-efficiency c-Si solar cells. In this article, a comprehensive study of atomic layer deposited (ALD) TiO x films is presented, including the processing as well as material, electrical and optical properties. The effects of deposition temperature from 100 to 400 °C and postdeposition annealing treatment on the properties of TiO x films are examined in terms of the ALD growth process and the composition, stoichiometry, crystallographic structure, bonding environment, elemental, chemical, electrical, and optical properties of the films. The screening of the temperature suggests that it is one of the key parameters that can be used to control the TiO x film properties for different applications, by giving excellent c-Si surface passivation with a surface recombination velocity as low as 3.7 cm/s. Further analysis of the underlying passivation mechanism suggests that TiO x films in amorphous phase combined with an interface oxide (SiO y +TiO x ) and a small amount of Cl are favorable for achieving good c-Si passivation. These findings significantly improve the fundamental understanding of TiO x films from their growth to application, and could enable the control of their properties for future device development.

Solution-processed and annealing-free zirconium acetylacetonate electron-selective contacts for efficient crystalline silicon solar cells

The interfaces between n-type silicon (n-Si) and metal electrode contact have enormous influences on the performance and stability of silicon solar cells. Recently, it has been proven that the carrier-selective contact (CSC) is an effective strategy to improve the device efficiency. Herein, a solution-processed and annealing-free zirconium acetylacetonate (ZrAcac) layer is used as an electron-selective contact for fabricating efficient crystalline silicon solar cell. This contact scheme enabled a reduction in both the contact resistivity and the work function at the interface between n-Si and Al, which can be attributed to the dipole formation at the contact interface induced by charge transfer. The application of this ZrAcac based contact was shown to consistently improve all device parameters reaching a maximum power conversion efficiency of 17.8% with a high fill factor of 81.1%, and greatly improve the device stability. This work demonstrated that the ZrAcac layer can provide sufficient energy alignment and enhanced carrier selectivity for efficient and stable photovoltaic devices.

Light-Promoted Electrostatic Adsorption of High-Density Lewis Base Monolayers as Passivating Electron-Selective Contacts.

Achieving efficient passivating carrier‐selective contacts (PCSCs) plays a critical role in high‐performance photovoltaic devices. However, it is still challenging to achieve both an efficient carrier selectivity and high‐level passivation in a sole interlayer due to the thickness dependence of contact resistivity and passivation quality. Herein, a light‐promoted adsorption method is demonstrated to establish high‐density Lewis base polyethylenimine (PEI) monolayers as promising PCSCs. The promoted adsorption is attributed to the enhanced electrostatic interaction between PEI and semiconductor induced by the photo‐generated carriers. The derived angstrom‐scale PEI monolayer is demonstrated to simultaneously provide a low‐resistance electrical contact for electrons, a high‐level field‐effect passivation to semiconductor surface and an enhanced interfacial dipole formation at contact interface. By implementing this light‐promoted adsorbed PEI as a single‐layered PCSC for n‐type silicon solar cell, an efficiency of 19.5% with an open‐circuit voltage of 0.641 V and a high fill factor of 80.7% is achieved, which is one of the best results for devices with solution‐processed electron‐selective contacts. This work not only demonstrates a generic method to develop efficient PCSCs for solar cells but also provides a convenient strategy for the deposition of highly uniform, dense, and ultra‐thin coatings for diverse applications.

Can interface charge enhance selectivity in tunnel layer passivated contacts? Using negatively charged aluminium oxide capped with dopant free PEDOT or boron doped polysilicon

Tunnel layer passivated contacts are widely used for selective extraction of electrons or holes in silicon solar cells. We investigate if a tunnel layer with high negative interface charge can further enhance the hole extraction ability (selectivity) of a passivated contact and thus the efficiency of silicon solar cells. High negative-charged, atomic layer deposited AlOx dielectric tunnel layers, capped with either conventional boron doped polysilicon (p+-poly-Si) or low-temperature, dopant-free poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), are investigated in order to form hole selective passivated contacts. Ultra-thin AlOx films in the tunnel regime (0.13–2 nm) are studied, measuring their passivation quality (τeff), fixed charge density (Qtot) and defect density (Dit) prior to capping, and contact recombination density (J0,contact) and effective contact resistivity (ρcontact) after capping with either PEDOT:PSS or p+-poly-Si. The measured J0,contact and ρcontact values are then used to calculate carrier selectivity and efficiency potential if rear-side integrated in a solar cell.Low temperature deposited PEDOT:PSS capped passivated contacts behave differently compared to high temperature deposited p+-poly-Si capped passivated contacts. Yes, negatively charged AlOx tunnel layers can enhance hole extraction capability/selectivity of a passivated contact. For PEDOT:PSS capped passivated contacts, the efficiency potential deploying optimized negatively charged AlOx tunnel layers (1.5 nm, annealed at 425 °C) was measured to be 1.1% higher than conventional reference-moderately charged SiOx tunnel layer (26% as compared to 24.9%). However, this is not observed for p+-poly-Si capped passivated contacts due to boron in-diffusion and associated charge compensation mechanism, a consequence of the high-temperature diffusion process.

Determining limitations of capacitance-voltage measurements of built-in voltage as an alternative to surface photovoltage for a-Si:H/c-Si heterojunctions

Strong band bending within crystalline silicon is important for improving carrier selectivity in the contact regions of silicon heterojunction solar cells. In this work, we compare the use of capacitance-voltage as an alternative to the surface photovoltage method for probing the built-in voltage associated with crystalline silicon band bending. The surface photovoltage technique is incapable of measuring structures with non-transparent contacts, while the capacitance-voltage technique shows saturation at high built-in voltages due to the formation of an inversion layer. The shift in built-in voltage and effect on open circuit voltage are demonstrated for variation across a range of amorphous Si p-doping levels. These experimental results are supported by simulation work, confirming the underlying band structure and carrier concentrations of photovoltaic Si heterojunctions and clarifying the limitations of capacitance measurements at high built-in voltages. Errors arising in capacitance-voltage measurements of these structures are explained and linked to deviations from the Mott-Schottky model approximations of a one-sided junction in full depletion.

Stable MoOX‐Based Heterocontacts for p‐Type Crystalline Silicon Solar Cells Achieving 20% Efficiency

AbstractCrystalline silicon heterojunction solar cells based on hole‐selective MoOX contacts provide obvious merits in terms of the decent passivation and carrier selectivity but face the challenge of long‐term stability. With the aim to improve the performance and stability of solar cells with full area MoOX/metal contacts, a SiOX tunneling layer on silicon surface is intentionally formed by UV/O3 treatment and an indium tin oxide (ITO) film is sputtered as a high‐work‐function electrode. Before ITO sputtering, an ultrathin V2OX capping layer is introduced to efficiently prevent MoOX film from air exposure and the damage by sputtering bombardment. The insertion of SiOX, V2OX, and ITO keeps the work function of MoOX at a high level, which improves the hole selectivity as well as the stability of the contact. The p‐Si/SiOX/MoOX/V2OX/ITO/Ag solar cell demonstrates an efficiency of 20.0% with improved stability, which is the highest value for MoOX heterocontacts class on p‐type silicon to date.

Hydrocarbon hydrogen carriers for catalytic transfer hydrogenation of guaiacol

Polycyclic hydrocarbons are known to be efficient hydrogen carriers capable of yielding high purity H2 upon dehydrogenation. Due to their high hydrogen density, high boiling point, and stability, these compounds demonstrate the potential to be used as hydrogen donors under catalytic transfer hydrogenation (CTH) conditions. In this work, the potential of a suite of hydrogen carriers to donate hydrogen, as well as the mechanisms affecting their hydrogen transfer, are assessed through the CTH of guaiacol, on Pd/Al2O3, as a model system. The results indicated the following descending order of transfer hydrogenation rate: bicyclohexyl > tetralin » hydrogenated terphenyl (HTP) > cyclohexylbenzene. Among the products, cyclohexanone and phenol are the most abundant, directly resulting from CTH. Detailed analysis of the hydrogen carrier conversion and selectivity clearly shows that the potential for CTH is highly linked to the molecular structure of the donor, rather than the amount of hydrogen available for transfer. A density functional theory (DFT) study, supported by experimental data, reveals that when unsaturated hydrocarbons are utilized, such as tetralin, cyclohexylbenzene, and HTP, the effective CTH rate to guaiacol is limited, despite dehydrogenation being more favorable for those molecules than from fully saturated donors, such as bicyclohexyl.

Versatility of Nanocrystalline Silicon Films: from Thin-Film to Perovskite/c-Si Tandem Solar Cell Applications

Doped hydrogenated nanocrystalline (nc-Si:H) and silicon oxide (nc-SiOx:H) materials grown by plasma-enhanced chemical vapor deposition have favourable optoelectronic properties originated from their two-phase structure. This unique combination of qualities, initially, led to the development of thin-film Si solar cells allowing the fabrication of multijunction devices by tailoring the material bandgap. Furthermore, nanocrystalline silicon films can offer a better carrier transport and field-effect passivation than amorphous Si layers could do, and this can improve the carrier selectivity in silicon heterojunction (SHJ) solar cells. The reduced parasitic absorption, due to the lower absorption coefficient of nc-SiOx:H films in the relevant spectral range, leads to potential gain in short circuit current. In this work, we report on development and applications of hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) from material to device level. We address the potential benefits and the challenges for a successful integration in SHJ solar cells. Finally, we prove that nc-SiOx:H demonstrated clear advantages for maximizing the infrared response of c-Si bottom cells in combination with perovskite top cells.