Carrier Selectivity Research Articles

Symmetric Dopant-Free Si Solar Cells Enabled by TiOx Nanolayers: An In-Depth Study on Bipolar Carrier Selectivity.

High-efficiency solar cells require two contact structures, engineered for efficient extraction of photogenerated holes and electrons at the respective electrodes. Herein, crystalline Si solar cell featuring hole- and electron-selective passivating contacts composed entirely of a single material, amorphous titanium oxide (TiOx), without extrinsic doping is demonstrated. The hole/electron selectivity of the TiOx layers (≈5 nm) is tailored by the oxidation process and the choice of Ti precursor in the atomic layer deposition (ALD). Ex situ and in situ X-ray photoelectron spectroscopy measurements elucidate that the hole-selective TiOx induces significant band bending in the Si (Φ≈0.7 eV), generating a p-type inversion layer in the n-Si absorber. The electron-selective TiOx induces a smaller band bending of Φ<0.35 eV. This clarifies that the bipolar carrier selectivity of TiOx is associated with the different amount of negative fixed charges generated during the ALD process, depending on the choice of Ti precursor and oxidant. In addition, the growth of a hydrogen-containing SiOy nanolayer (≈1-1.5 nm) at the Si/TiOx interface during postdeposition oxidation is crucial for providing chemical passivation in both types of TiOx. These findings pave the way for a deeper understanding of the charge generation mechanism and chemistry at the Si/metal oxide interfaces.

Simulation of the functionality of ZnO, TiO2 and Ta2O5, and MoO2 carrier selective contacts of GaAs0.99Bi0.01 nanowire-based solar cells

Abstract Photovoltaic performance of perpendicularly aligned GaAs0.99Bi0.01/CSC/ITO core-shell nanowire solar cell is thoroughly investigated in this simulation based theoretical study for both electron selective contact (ESC) and hole selective contact (HSC) as carrier selective contact (CSC) shell around GaAs0.99Bi0.01 core nanowire. The overall performance has been compared with radial PiN doped GaAs0.99Bi0.01 NWSC to mark the improvement caused by carrier selectivity. ZnO, TiO2, and Ta2O5 materials have been chosen as ESC material and MoO2 is chosen as HSC material in order to carry out this comparative study. We have thoroughly performed geometry optimization test over a wide range of periods in order to select the optimized ITO (Indium Tin Oxide) thickness for obtaining maximum photo current generation. The maximum short circuit photo current density (Jsc) of 38.76 mA/cm2 is obtained with ZnO coated nanowire solar cell (NWSC) for a pitch (P) of 400 nm and ITO shell thickness of 90 nm. For this optimized geometry, TiO2, Ta2O5 and MoO2 coated structures offered Jsc of 35.82 mA/cm2, 35.69 mA/cm2, and 35.27 mA/cm2 respectively and the uncoated NW generated Jsc of 31.15 mA/cm2. The planar structure without coating exhibits a Jsc of 24.86 mA/cm2, which is significantly lower than the nanostructured solar cells. Finally Lumerical 3D charge transport simulator is used to perform the electrical stimulation of ZnO coated structure, which offers maximum ideal Jsc. A detailed electrical performance analysis of GaAs0.99Bi0.01/CSC/ITO unit nanowire solar cell for ZnO, TiO2, Ta2O5 as ESC and MoO2 as HSC have also been covered in this article which reveals that ZnO as ESC possesses promising potential for designing highly efficient solar cells as it offers a photo conversion efficiency(PCE) of the order of 25% and open circuit voltage (Voc) even for very less minority carrier lifetime (Ʈn) 0.1 ns of GaAs0.99Bi0.01 and 1ps Ʈn of ZnO.

Enhanced Carrier Selectivity and Superior Passivation in Cost‐Effective Heterogeneous Hybrid Transport Layers for Next Generation Silicon Solar Cells

AbstractHybrid hole transport layers (HHTLs) consisting of‐a low‐cost, low‐temperature, dopant‐free, organic, hole‐selective poly(3,4‐ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS) and an inorganic homogenous tunnel oxides (HoTOs), such as SiOx, TiOx, and AlOx have allowed significant improvements in carrier selectivity as well as in power and cost efficiency. These key parameters can be further improved by introducing heterogeneous tunnel oxides (HeTOs), formed of two different inorganic oxides. This work examines the potential of heterogeneous HHTLs and their impact on passivation as well as on the interfacial properties in silicon solar cells. HeTOs of SiOx/TiOx and SiOx/AlOx with negative fixed charge are studied and optimized. A heterogeneous HHTL with AlOx (&gt;1.5 nm) resulted in a high lifetime (1.2 ms), low surface recombination velocity, and improved surface band bending at the interface due to the presence of higher negative fixed charge (1012 cm−2) within these layers. The passivation properties further improved on light soaking and annealing due to oxidation of PSS and AlOx/SiOx. Overall, these HHTLs demonstrated a hole selectivity (S10) of 12.5 and very high efficiencies up to of 26.1%, surpassing homogenous‐SiOx/PEDOT:PSS by 1.4%.

Electrical Performance, Loss Analysis, and Efficiency Potential of Industrial‐Type PERC, TOPCon, and SHJ Solar Cells: A Comparative Study

ABSTRACTCurrently, the efficiency of p‐type passivated emitter and rear contact (PERC) cells has been growing at an absolute efficiency of 0.5% per year and has reached 23%–23.5% in mass production while getting closer to its theoretical efficiency limit. n‐Type tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ) cells with their superior “passivating selective contacts” technology were the most interesting photovoltaics (PV) technology in the industry. The effect of different passivated contact layers with respect to their influence on the J0, J0,metal, ρc, and the carrier selectivity (S10) and the loss analysis and efficiency potential of industrial‐type PERC, TOPCon, and SHJ solar cells were studied and compared. The results showed that TOPCon structure with a high passivation performance and good optical performance is more suitable for bifacial solar cell and the highest theoretical limiting efficiency with metal shading on the n‐type Si wafer (ηb,e,h,m,max) can be achieved to 27.62%. Although SHJ structure with the highest passivation performance but the worst optical performance owing to the parasitic absorption of a‐Si:H layer and high contact resistivity, the value of ηb,e,h,m,max is 0.7% lower than that of TOPCon solar cells. PERC structure has superior optical performance than SHJ structure, but due to poor passivation performance, the ηb,e,h,m,max is only 26.42%. The next‐generation products may be heterojunction back‐contact (HBC) and TOPCon back‐contact (TBC) cells with high ηb,e,h,m,max of 28.12% and 27.99%, respectively. Exploiting a perfect passivation of the noncontact area, the wide process window and low cost are required and transferring these new concepts to industrial solar cell production will be the next major challenge.

Tunnel oxide passivating contact enabled by polysilicon on ultra-thin SiO2 for advanced silicon radiation detectors

Conventional silicon junction detectors encounter significant carrier recombination within the heavily doped p+ and n+ layers, as well as beneath the metal contact regions, creating the so-called “dead layers”, especially on the detector side. In this study, we present the tunnel oxide passivating contact with doped polysilicon on oxide, which demonstrates exceptional surface passivation and carrier selectivity. The key innovation lies in an ultra-thin (~ 1.5 nm) interfacial oxide layer that facilitates efficient majority carrier transportation via tunneling while effectively block minority carriers. Remarkably low saturation current densities, ranging from 5 to 10 fA/cm2 even with the metal contact, underscore the superiority of both n-type and p-type tunnel oxide passivating contacts. In contrast, conventional p–n junction or high-low junction exhibit saturation current densities ranging from 10 to 90 fA/cm2 in the studied p+ and n+ layers with surface passivation schemes due to Auger recombination and surface recombination, and 1000–6000 fA/cm2 with metal contacts due to intense metal-induced recombination at the interface. These findings indicate the potential and superiority of implementing n-type tunnel oxide passivating contact on the detector side and p-type contact on the back side for advanced silicon radiation detectors. This approach would enable thorough collection of generated charge carriers along the track of incident ionizing radiation particles, leading to improved energy resolution and reduced noise levels.

Continuous distribution of interface states in n-type double-side poly-Si/SiOx passivating contact solar cells

Advanced passivation contact in high-efficiency silicon solar cells plays an important role for the sake of minimizing recombination losses. A stack of heavily doped polycrystalline silicon (poly-Si) and tunnel SiOx contact has attracted much attention, benefitting from its excellent characteristics of carrier selectivity and passivation, and which has been successfully applied in double-side poly-Si/SiOx passivating contact solar cells. Note that characteristics analysis of defects at tunnel SiOx/c-Si (crystalline silicon) interface remains an issue of concern. Herein, we observe capacitance transient spectroscopy arise from both electron and hole traps in the passivating contact structure of poly-Si(p+)/tunnel SiOx/c-Si(n). Subsequently, we propose a skillful procedure of deep-level transient spectroscopy (DLTS) measurement to confirm that the observed electron and hole traps are located at the tunnel SiOx/c-Si interface but not in the bulk of the c-Si substrate. Finally, we show a clear physical picture of continuous energy distribution for interface states.

Development of high conducting phosphorous doped nanocrystalline thin silicon films for silicon heterojunction solar cells application

We have investigated the plasma-enhanced chemical vapor deposition growth of the phosphorus-doped hydrogenated nanocrystalline silicon (n-nc-Si:H) film as an electron-selective layer in silicon heterojunction (SHJ) solar cells. The effect of power densities on the precursor gas dissociation are investigated using optical emission spectra and the crystalline fraction in n-nc-Si:H films are correlated with the dark conductivity. With the P d of 122 mW cm−2 and ∼2% phosphorus doping, we observed Raman crystallinity of 53%, high dark conductivity of 43 S cm−1, and activation energy of ∼23 meV from the ∼30 nm n-nc-Si:H film. The n-nc-Si:H layer improves the textured c-Si surface passivation by two-fold to ∼2 ms compared to the phosphorus-doped hydrogenated amorphous silicon (n-a-Si:H) layers. An enhancement in the open-circuit voltage and external quantum efficiency (from >650 nm) due to the better passivation at the rear side of the cell after integrating the n-nc-Si:H layer compared to its n-a-Si:H counterpart. An improvement in the charge carrier transport is also observed with an increase in fill factor from ∼71% to ∼75%, mainly due to a reduction in electron-selective contact resistivity from ∼271 to ∼61 mΩ-cm2. Finally, with the relatively better c-Si surface passivation and carrier selectivity, a power conversion efficiency of ∼19.90% and pseudo-efficiency of ∼21.90% have been realized from the SHJ cells.

Influence of highly optimized charge carrier mobility and diverse physical features toward efficient organic solar cells

Organic solar cells (OSCs) exhibit potential in low-emissive photovoltaic (PV) technology by enhancing excitonic absorption, higher trap-assist recombination, lower excitons diffusion length (Ln,p), and carrier lifetime (τ n,p). The main challenge remains the asymmetric carrier mobility (μ n,p) of the organic absorbing layer (OAL) and various physical factors affecting efficiency (η). This effort has been explored through the attributes of different fullerene derivatives based on binary blends of OAL thickness that suggest new physical insights into the roles of several contributions in the PV performances under intense light illumination. The relationship between optimum mobility ratio (β) and lower trap-state density (Nt) of OAL in OSC structures for inclusive η has been collectively investigated. With a very thin OAL and pioneering transparent hole transport layers (HTLs) can significantly reduce recombination loss and enhance transparency, focusing on near-infrared band absorption and thin hetero-interface design for η and stability. The improved thin OALs, tunable absorption bands, and carrier selectivity address efficiency–transparency trade-offs and reproducibility concerns. The outcome revealed a stable η of 6.27% with a 250 nm thinnest OAL at a temperature of 300 K, which may be interpreted as a coupled framework for effective optimization strategies to accomplish balance between photogeneration and charge carrier recombination. Thus, the observed hypothetically analyzed results have verified the further optimization of OAL thickness for fabrication perspectives with a typical interpretation of ohmic contact.

Sn‐Doped Nb2O5Films as Effective Hole‐Selective Passivating Contacts for Crystalline Silicon Solar Cells

Carrier‐selective contacts (CSCs) in crystalline silicon (c‐Si) solar cells have attracted great attention due to suppressing contact region recombination and achieving higher conversion efficiency. Among transition metal oxides for CSCs, niobium oxide (Nb2O5) is considered as an attractive candidate for electron‐selective contact due to its excellent passivation properties and small conduction band offsets with c‐Si. Nevertheless, the performance of c‐Si solar cells employing Nb2O5contact layer has not been explored yet. Herein, the carrier selectivity of solution‐processed Nb2O5films is investigated for c‐Si. Interestingly, Nb2O5exhibits high electron‐blocking performance and low contact resistivities with p‐Si. The ultra‐thin SiOxinterlayer formed by UV–O3pretreatment further reduces the contact resistivities and increases minority carrier lifetime due to the improved contact interface. The Sn4+doping improves the work function of Nb2O5to induce larger upward band bending at c‐Si surface, thus enhancing the hole selectivity. As a result, p‐type c‐Si solar cells with solution‐processed Nb2O5hole‐selective contact layer have achieved the highest power conversion efficiency of 18.4%, with a high‐thermal stability superior to the typical hole transport layers. This work first demonstrates the exceptional hole selectivity of Nb2O5, which shows very promising applications in high‐efficiency c‐Si solar cells.

Interfacial fixed charges and dipoles to boost carrier selectivity for crystalline silicon solar cells

&lt;p&gt;With the rapid evolution of passivating contact, the carrier transport layer in crystalline silicon (&lt;i&gt;c&lt;/i&gt;-Si) solar cells has expanded beyond the doped silicon films to non-silicon films with lower parasitic absorption and manufacturing cost. However, using the emerging carrier transport layers in direct contact with &lt;i&gt;c&lt;/i&gt;-Si suffers from the insufficient carrier selectivity, which limits the efficiency of the device. Thus, to make such new strategies practical, it becomes particularly important to enhance the passivation quality and thus minimize the recombination losses at &lt;i&gt;c&lt;/i&gt;-Si surfaces. By introducing interfacial fixed charges (&lt;i&gt;Q&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;) or dipoles on the &lt;i&gt;c&lt;/i&gt;-Si surface, the local electric field can be tuned to affect the recombination and charge carrier transport dynamics. This perspective highlights the significance of interfacial &lt;i&gt;Q&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; and dipoles for carrier selectivity, and points out the challenges in a comprehensive understanding of the mechanism and precisely controlling the carrier behavior as well as the solar cell stability.&lt;/p&gt;

Influence of passivating interlayers on the carrier selectivity of MoOx contacts for c-Si solar cells

The application of molybdenum oxide (MoOx) as a hole-selective contact for silicon-based solar cells has been explored due to superior optical transmittance and potentially leaner manufacturing compared to fully amorphous silicon-based heterojunction (SHJ) devices. However, the development of MoOx contacts has been hampered by their poor thermal stability, resulting in a carrier selectivity loss and an S-shaped IV curve. The aim of this study is to understand the influence of different passivating interlayers on the carrier selectivity of hole-selective MoOx contacts for crystalline silicon (c-Si) solar cells. We highlight the effect of different interlayers on the surface passivation quality, contact selectivity, and the thermal stability of our MoOx-contacted devices. The interlayers studied are intrinsic hydrogenated amorphous silicon (a-Si:H(i)), thermally grown ultrathin SiO2, and a stack consisting of an ultrathin SiOy and Al2O3 layer. Additionally, we simulate the interacting interlayer properties on the carrier selectivity of our MoOx contacts using a simplified model. Among these interlayers, the Al2O3/SiOy stack shows to be a promising alternative to SiO2 by enabling efficient transport of holes while being able to sustain an annealing temperature of at least 250 °C underlining its potential in module manufacturing and outdoor operation.

Enhancing the Selectivity and Transparency of the Electron Contact in Silicon Heterojunction Solar Cells by Phosphorus Catalytic Doping

AbstractAn intrinsic hydrogenated amorphous silicon (a‐Si:H(i)) film and a doped silicon film are usually combined in the heterojunction contacts of silicon heterojunction (SHJ) solar cells. In this work, a post‐doping process called catalytic doping (Cat‐doping) on a‐Si:H(i) is performed on the electron selective side of SHJ solar cells, which enables a device architecture that eliminates the additional deposition of the doped silicon layer. Thus, a single phosphorus Cat‐doping layer combines the functions of two other layers by enabling excellent interface passivation and high carrier selectivity. The overall thinner layer on the window side results in higher spectral response at short wavelengths, leading to an improved short‐circuit current density of 40.31 mA cm−2 and an efficiency of 23.65% (certified). The cell efficiency is currently limited by sputter damage from the subsequent transparent conductive oxide fabrication and low carrier activation in the a‐Si:H(i) with Cat‐doping. Numerical device simulations show that the a‐Si:H(i) with Cat‐doping can provide sufficient field effect passivation even at lower active carrier concentrations compared to the as‐deposited doped layer, due to the lower defect density.

Design Rule of Electron- and Hole-Selective Contacts for Polycrystalline Silicon-Based Passivating Contact Solar Cells.

A crystalline silicon (c-Si) solar cell with a polycrystalline silicon/SiOx (poly-Si/SiOx) structure, incorporating both electron and hole contacts, is an attractive choice for achieving ideal carrier selectivity and serving as a fundamental component in high-efficiency perovskite/Si tandem and interdigitated back-contact solar cells. However, our understanding of the carrier transport mechanism of hole contacts remains limited owing to insufficient studies dedicated to its investigation. There is also a lack of comparative studies on the poly-Si/SiOx electron and hole contacts for ideal carrier-selective solar cells. Therefore, this study aims to address these knowledge gaps by exploring the relationship among microstructural evolution, dopant in-diffusion, and the resulting carrier transport mechanism in both the electron and hole contacts of poly-Si/SiOx solar cells. Electron (n+ poly-Si/SiOx/substrate)- and hole (p+ poly-Si/SiOx/substrate)-selective passivating contacts are subjected to thermal annealing. Changes in the passivation properties and carrier transport mechanisms of these contacts are investigated during thermal annealing at various temperatures. Notably, the results demonstrate that the passivation properties and carrier transport mechanisms are strongly influenced by the microstructural evolution of the poly-Si/SiOx layer stack and dopant in-diffusion. Furthermore, electron and hole contacts exhibit common behaviors regarding microstructural evolution and dopant in-diffusion. However, the hole contacts exhibit relatively inferior electrical properties overall, mainly because both the SiOx interface and the p+ poly-Si are found to be highly defective. Moreover, boron in the hole contacts diffuses deeper than phosphorus in the electron contacts, resulting in deteriorated carrier collection. The experimental results are also supported by device simulation. Based on these findings, design rules are suggested for both electron and hole contacts, such as using thicker SiOx and/or annealing the solar cell at a temperature not exceeding the critical annealing temperature of the hole contacts.

Surface Modification of ITO with N-Heterocyclic Carbene Precursors Results in Electron Selective Contacts in Organic Photovoltaic Devices.

Surface modification of indium tin oxide (ITO) electrodes with organic molecules is known to tune their work function which results in higher charge carrier selectivity in corresponding organic electronic devices and hence influences the performance of organic solar cells. In recent years, N-heterocyclic carbenes (NHCs) have also been proven to be capable to modify the work function of metals and semimetals compared to the unfunctionalized surface via the formation of strong covalent bonds. In this report, we have designed and performed the modification of the ITO surface with NHC by using the zwitterionic bench stable IPr-CO2 as the NHC precursor, applied via spin coating. Upon modification, the work function of ITO electrodes was reduced significantly which resulted in electron selective contacts in corresponding organic photovoltaic devices. In addition, various characterization techniques and analytical methods are used to elucidate the nature of the bound species and the corresponding binding mechanism of the material to the ITO surface.

Mechanisms for Charge Selectivity on Semiconducting Photocatalyst Particles

Overall-water splitting on photocatalysts provides a direct-unassisted path in the conversion of solar energy to chemical energy. Optoelectronic properties (absorbing incident light with long excited state lifetimes) and carrier selective contacts (transporting and transferring the desired electronic carrier to the targeted redox active species) are two key parameters that govern photocatalyst behavior. However, the advantageous small geometry of the highest achieving photocatalysts makes measurement of their carrier selective contacts difficult. Additionally, several mechanisms that enable high energy-conversion efficiencies and large gradients in free energy manifest only at the nanoscale at individual nanoparticle sites. SrTiO3 has been extensively studied and shown to split water with high quantum yields when decorated with HER and OER catalysts. SrTiO3 is used, in this work, as a model system to study mechanisms for charge selectivity on overall-water splitting photocatalyst particles.Here, we use three sample geometries to measure local, facet, and catalyst-dependent, electrochemical driving forces and their synergistic enhancement of carrier selectivity, (single crystal planar (b), single crystal co-facet exposed planar (a), facetted nanoparticles (c) loaded with OER and HER catalysts [{Pt/CrO3, Rh/CrO3} and CoOOH respectively]). We use ex-situ conductive atomic force microscopy to individually interrogate the electrical properties of nano-scale catalyst/semiconductor junctions decorated on facet-engineered surfaces of SrTiO3. Supporting experiments of SECM and Operando AP-XPS will be used to measure the charge carrier selectivity when an electrolyte is present and connect the ex-situ characterization observations to operando conditions. In summary, these findings demonstrate the underlying mechanisms and the degree that they play, enabling directed research of photocatalyst systems under the two dominant engineering conditions, high optoelectronic properties and charge selective contacts. Figure 1

Understanding Contact Nonuniformities at Interfaces in Perovskite Silicon Tandem Solar Cells Using Luminescence Imaging, Lock‐In Thermography, and 2D/3D Simulations

The top cell of a perovskite silicon tandem solar cell requires several material layers on each side of the perovskite absorber to efficiently extract electrons and holes, respectively. These layers must meet multiple requirements simultaneously, namely, low interface recombination, good charge carrier selectivity, low contact resistivity, and high optical transparency. Due to the complex architecture, characterization techniques are required in material and process optimization to identify loss mechanisms. Spatial resolution of the characterization is gaining importance along with the upscaling of the perovskite technology. Herein, electro‐ and photoluminescence (EL and PL) imaging is combined with illuminated lock‐in thermography (ILIT) for a comprehensive electro‐optical characterization of both subcells in perovskite silicon tandem devices with state‐of‐the‐art cell architecture. Thereby, the combination of the presented characterization methods together with numerical simulation models enables to carry out holistic investigations of device limitations. The strength of this approach is showcased by one particularly remarkable feature that is observed in the investigated tandem device, showing a low PL but high EL signal at local spots. Together with multidimensional optoelectrical device simulations, the measurements are explained and the root cause of this feature to originate from the perovskite/C60 interface is suggested.

Gradient doping in Cu2ZnSnSe4 by temperature and potential induced defect steering

Kesterite materials are among the most promising emerging photovoltaic absorbers, despite the number of challenging issues this technology presents. The use of soft thermal post-deposition treatments is key to improving the CdS/kesterite interface quality. Thermal treatments can result in a low-temperature phase transition which affects the optoelectronic properties. In this work, the effects of applied voltage during a full device thermal post-deposition treatments above the critical temperature of the phase transition are explored. The applied voltage modifies the formation energy and drives in-depth migration of ionized defects, which can generate a shallow doping density gradient. Supporting the experimental findings, the effects of a shallow doping density gradient on the current–voltage curves and the external quantum efficiency are modelled using drift–diffusion calculations. The presence of bulk recombination centers in the modelling is a key aspect to precisely reproduce the experimental results. The shallow doping density gradient in opposite directions precisely matches the experimental results for opposite voltage polarizations. The effects on the band structure of the device are presented proving this as a promising strategy for improving charge carrier selectivity.This is the first time that a defect engineering approach has been proposed and successfully proven to control shallow doping density profiling and improve the charge carrier selectivity of kesterite devices. In this sense, the results and their thorough physical interpretation presented in this work will potentially open new perspectives in other photovoltaic technologies as well as in the field of materials engineering.

In situ growth MoS2 quantum dots as promising interface materials for silicon solar cells

The carrier selectivity at interface is one key factor to improve the performance of silicon solar cells. Here, Molybdenum disulfide (MoS2) quantum dots were successfully synthesized by one-step in situ plasma enhanced atom layer deposition. A transmission electron microscope was employed to investigate nano-size scaled as well as growth mechanism of the crystalline MoS2 quantum dots. MoS2 quantum dots with additional molybdenum-oxygen (Mo–O) bonding were prepared by co-reactant plasma processing, which exhibited photo-generated carrier selectivity as promising interface materials for silicon heterojunction solar cells. Our results indicated their carrier selectivity of electron-blocking and hole-transporting at interface was attributable to unique quantum effects and tunneling effects. A photovoltaic conversion efficiency 23% was achieved by a sample silicon solar cell combined with MoS2 quantum dots interface materials. Because the interface engineering is well-defined, and the synthesis is low-cost, this bottom-up strategy provides a potential advance in design and construction of innovative and highly efficient photovoltaic devices.

Ultrathin Al-doped SiO x passivating hole-selective contacts formed by a simple wet process

Ultrathin Al-doped Si oxide (SiO x ) layers were formed by a simple wet chemical treatment, and their hole-selective passivating contact and electrical properties were investigated. From the evaluated contact resistivity (ρ c) and saturation current density (J 0), carrier selectivity (S 10) was estimated to be 13.3. Moreover, in Si nitride (SiN y )/Al-doped SiO x stacks, negative values of fixed charge density (Q f) were obtained, despite a high positive Q f existing in the single SiN y layer. This result implies that Al-doped SiO x has high negative fixed charges and overcompensates the charge polarity in the stacks, which forms an inversion layer and accumulates holes on the Si surface. Furthermore, the negative fixed charges realize excellent carrier separation by the induced upward band bending. In addition, we proposed a novel device architecture named Al-induced charged oxide inversion layer solar cells and confirmed device operation in a simple device configuration.

Reducing Nonradiative Losses in Perovskite LEDs through Atomic Layer Deposition of Al2O3 on the Hole-Injection Contact.

Halide perovskite light-emitting diodes (PeLEDs) exhibit great potential for use in next-generation display technologies. However, scale-up will be challenging due to the requirement of very thin transport layers for high efficiencies, which often present spatial inhomogeneities from improper wetting and drying during solution processing. Here, we show how a thin Al2O3 layer grown by atomic layer deposition can be used to preferentially cover regions of imperfect hole transport layer deposition and form an intermixed composite with the organic transport layer, allowing hole conduction and injection to persist through the organic hole transporter. This has the dual effect of reducing nonradiative recombination at the heterojunction and improving carrier selectivity, which we infer to be due to the inhibition of direct contact between the indium tin oxide and perovskite layers. We observe an immediate improvement in electroluminescent external quantum efficiency in our p-i-n LEDs from an average of 9.8% to 13.5%, with a champion efficiency of 15.0%. The technique uses industrially available equipment and can readily be scaled up to larger areas and incorporated in other applications such as thin-film photovoltaic cells.