We report efficiencies of >24% being consistently achieved in mass-production of passivating-contact solar cells. Furthermore, the certified efficiency of cells from our pilot line has reached 25.3% with 730 mV open-circuit voltage. An analysis of the cell performance, including simulations, shows that the cells’ rear-side is nearly ideal, while there remains potential for further optimization of the front emitter and passivation.

In recent years, we have developed the Q.ANTUM NEO solar cell, a rear-passivated double-sided contact solar cell that achieves power conversion efficiencies exceeding 25.5 %. Our streamlined and cost-efficient process leverages the proprietary Laser Enhanced Contact Optimization (LECO) technology. The LECO process has undergone extensive optimization and has been successfully implemented in both our pilot line and mass production facilities, resulting in significant improvements in solar cell efficiency. LECO facilitates a novel formation of the contact interface between the silicon surface and metallization, leading to remarkably low j0,met values (as low as 160 fA cm(- 2)). The contact resistivity of 20 mu m wide contacts on a high sheet resistance emitter is below 1 m Omega cm(2), with minimal impact on fill factor (FF) and overall cell efficiency. Rigorous reliability tests, including TC600 and DH3000, demonstrate module degradation well below 5%rel. Our champion cell conversion efficiency achieved in the pilot line using LECO technology reaches 25.6 %, accompanied by a notable open-circuit voltage exceeding 730 mV.

Within this work, both the performance and reliability of industrial Boron- and Gallium-doped p-type monocrystalline silicon solar cells with dielectrically passivated rear side with an average conversion efficiency of 23.6 % are investigated. Currently, in the p-type wafer market, mainly Gallium-doped material is available. Only a few studies on the so-called "Light and elevated Temperature Induced Degradation" (LeTID) of this material are available in literature. It is advertised that the well-known degradation effect caused by boron-oxygen can be avoided by using gallium as dopant. This work shows that, if not adequately suppressed, LeTID can also occur in Gallium-doped p-type Czochralski silicon passivated emitter and rear solar cells with a degradation in cell and module output power of up to 3 %(rel), which cannot be significantly suppressed in a straightforward manner by conventional processing steps to permanently deactivate the light-induced degradation defect. We demonstrate the possibility to reduce LeTID significantly on Boron- and Gallium-doped p-type monocrystalline solar cells and modules by adapting the cell process and processing sequence.

Methods of making silicon based tandem cells include wafer bonding, depositing absorber layers on the surface, and mechanical stacking. Of these, mechanically stacking after growth retains the individual cell quality during production, but typically requires a four-terminal device. We present a transparent conductive adhesive (TCA) interlayer, designed for transparency in wavelengths that Si absorbs, conductivity for out-of-plane conductivity between cells, and adhesive strength, enabling two-terminal stacked tandems. The developed TCA material is a polymer-particle blend of common transparent adhesives and metal-coated flexible microspheres, capable of bridging micro-scale gaps between uneven/textured surfaces. At 10% microsphere coverage, experimental and theoretical series resistance is compatible with high-efficiency tandem cells on silicon.

This paper proposes to use machine learning (ML) methods to predict wafer quality using Fab inline measured items, DC measurements, and DVS (Dynamic Voltage Stress) at wafer sort. With developed ML approach, the predicted accuracy is more than 80% in 8 nm products used in this study. We believe this method can be further fine-tuned to help enable ICs at the high level expected for automotive systems. By assigning predictive rankings, the method also helps enable best tooling system for higher quality.

Hanwha Q CELLS has developed bifacial p-Cz PERC cells with average efficiency in mass production above 22%, measured with 1000 W/m(2) front illumination. The bifaciality factor of the cells is determined to be 78%. A comparison of bifacial vs. equivalent monofacial cells shows that the bifacial cells have slightly lower front efficiency by 0.1%. However, at the module-level there is essentially no gap in front power performance of bifacial vs. monofacial, due to a better cell-to-module ratio for bifacial. Bifacial modules with 144 half-cells having average power of 390 W on the front and 286 W rear are demonstrated.

Cloud storage applications, such as Dropbox and Google Drive, have recently become very popular among mobile users. In these applications, a cloud server is responsible for synchronizing updates to files among mobile users, and thus if files are shared by many mobile users and are frequently updated then the resulting synchronization traffic can be significant. In order to reduce the synchronization traffic with providing acceptable access latency, we propose a fog-assisted aggregated synchronization (FAS) scheme in which the fog computing server and the cloud server conduct localized and aggregated synchronizations, respectively. We develop an analytical model of the FAS scheme based on renewal-reward theory and use it for model-based adjustment of the timer that controls the trade-off between access latency and synchronization traffic. We use analytical and simulation results to give insight into the effects of the timer, the update-to-access ratio, the number of mobile users, and the sensitivity to the arrival process. The analytical and simulation results demonstrate that the FAS scheme can reduce the synchronization traffic significantly with acceptable access latency compared to conventional schemes.

We report quantum chemical calculations using multireference perturbation theory (MRPT) with the density matrix renormalization group (DMRG) plus photo thermal deflection spectroscopy measurements to investigate the manifold of carotenoid excited states and establish their energies relative to the bright state (S-2) as a function of nuclear reorganization. We conclude that the primary photophysics and function of carotenoids are determined by interplay of only the bright (S-2) and lowest-energy dark (S-1) states. The lowest-lying dark state, far from being energetically distinguishable from the lowest-lying bright state along the entire excited-state nuclear reorganization pathway, is instead computed to be either the second or first excited state depending on what equilibrium geometry is considered. This result suggests that, rather than there being a dark intermediate excited state bridging a non-negligible energy gap from the lowest-lying dark state to the lowest-lying bright state, there is in fact no appreciable energy gap to bridge following photoexcitation. Instead, excited-state nuclear reorganization constitutes the bridge from S-2 to S-1 in the sense that these two states attain energetic degeneracy along this pathway.

Transparent conductive adhesives (TCAs) can enable conductivity between two substrates, which is useful for a wide range of electronic devices. Here, we have developed a TCA composed of a polymer-particle blend with ethylene-vinyl acetate as the transparent adhesive and metal-coated flexible poly(methyl methacrylate) microspheres as the conductive particles that can provide conductivity and adhesion regardless of the surface texture. This TCA layer was designed to be nearly transparent, conductive in only the out-of-plane direction, and of practical adhesive strength to hold the substrates together. The series resistance was measured at 0.3 and 0.8 Ω cm2 for 8 and 0.2% particle coverage, respectively, while remaining over 92% was transparent in both cases. For applications in photovoltaic devices, such as mechanically stacked multijunction III-V/Si cells, a TCA with 1% particle coverage will have less than 0.5% power loss due to the resistance and less than 1% shading loss to the bottom cell.

This work addresses the latest performance of Hanwha Q CELLS industrially manufactured p-type monocrystalline silicon solar cells with dielectric-passivated rear side and the corresponding modules. Results of Q. ANTUM solar cell performance are presented, proving the feasibility of PERC-like (Passivated Emitter and Rear Cell) solar cells with solar cell conversion efficiency exceeding 22.0% in mass production while maintaining a lean and cost-effective process flow with only few more process steps compared to Al-BSF solar cells (Aluminum Back Surface Field). On module level, additional power-enhancing measures are implemented at Hanwha Q CELLS mass production sites, including the interconnection of half-sized cells by wires instead of ribbons. In total, both the high solar cell conversion efficiency and the implemented module measures enable the industrial manufacturing of 120 half-cell modules with module power classes of mostly 320 Wp and 325 Wp with the use of standard p-type Czochralski-grown silicon wafers. Indeed, modules even exceeding 330 Wp have also been fabricated.

Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here, we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a poly(lauryl methacrylate) polymer layer with embedded cadmium selenide core, cadmium sulfide shell (CdSe/CdS) quantum dot (QD) luminophores and an InGaP microcell array, which serves as high bandgap absorbers on the top of a conventional Si photovoltaic. We investigate the design space for a tandem LSC, using experimentally measured performance parameters for key components, including the InGaP microcell array, CdSe/CdS QDs, and spectrally selective waveguide filters. Using a Monte Carlo ray-tracing model, we compute the power conversion efficiency for a tandem LSC module with these components to be 29.4% under partially diffuse illumination conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic cell.

The charge carrier transport mechanism of passivating contacts which feature an ultra-thin oxide layer is investigated by studying temperature-dependent current-voltage characteristics. 4-Terminal dark J-V measurements at low temperatures reveal non-linear J-V characteristics of passivating contacts with a homogeneously grown silicon oxide, which result in an exponential increase in contact resistance towards lower temperature. The attempt to describe the R(T) characteristic solely by thermionic emission of charge carriers across an energy barrier leads to a significant underestimation of the resistance by several orders of magnitude. However, the data can be described properly with the metal-insulator-semiconductor (MIS) theory if tunneling of charge carriers through the silicon oxide layer is taken into account. Furthermore, temperature-dependent light J-V characteristics of solar cells featuring passivating contacts at the rear revealed a FF drop at T < 205 K, which is near the onset temperature of the exponential increase in contact resistivity.

Hanwha Q CELLS now produces its high-efficiency Q.ANTUM solar cell and module technology with p-type Czochralski-grown silicon (Cz-Si) on a multi-GW scale. While maintaining a lean fabrication process, average cell efficiencies exceeding 22 % are achieved in mass production. This results in module powers of more than 330 W by applying wire-based cell interconnection technology to 120 half 6-inch Q.ANTUM cells, narrowing the gap to the highest-efficiency module technologies which use n-type silicon solar cells, at an extremely competitive manufacturing cost. In contrast to conventional passivated emitter and rear cells (PERC), Hanwha Q CELLS' Q.ANTUM technology is shown to reliably suppress both light-induced degradation (LID) due to boron-oxygen defect formation and Light and elevated Temperature Induced Degradation (LeTID).

We propose a design for a concentrated photovoltaic (CPV) module with features that can capture both direct and diffuse sunlight. This approach uses a luminescent solar concentrator (LSC) sheet that includes quantum dots, and a tailored optical coating that enhances concentration and delivery of sunlight to the micro-PV cells. In addition, the light not captured by the quantum dots impinges on a tandem solar cell beneath the LSC sheet. The design of the LSC focuses on lowering the number of expensive micro-PV cells needed within the concentrator waveguide, thus reducing system costs while maintaining high efficiency. The design also allows the module to be effective without a tracking system, making it attractive to all PV markets.

We report on the application of analytical microscopy to identify material bottlenecks for silicon solar cell efficiency on an atomic scale, including contacts, interfaces, and passivating layer morphologies. With high lifetime bulk n-Cz wafers available on a mass production scale, the push for higher efficiency (> 20%) is focused on passivation and reduced recombination at the metal contacts. These stringent passivation requirements should be retained during the subsequent device processing. Our device structures involve n-Cz silicon wafers with passivated contacts (poly-Si/SiO2/n-Cz), and Al2O3/SiNx front surface passivation layers, designed for incorporation into IBC solar cells. Using analytical microscopy, we study failure modes from the macroscopic scale (blisters in the passivation layers, metal adhesion problems) thru the microscopic (micropyramids, microblisters, microcracks) down to the nanoscale (nanopinholes, precipitates, blister edges, grain boundary decoration by dopants, dopant distribution) and atomic scale (dopant aggregation on surfaces and interfaces, atomic bonding valence and character). Metallization degrades our passivated contacts by promoting blistering along the poly-Si/SiO2 interface, which is shown in detail by dissecting blisters and mapping them from a micron-to atomic scale using aberration corrected scanning transmission electron microscopy. A fundamental materials understanding focused on the effects of device processing, especially metallization, on retaining high-efficiency passivated Si devices is therefore gained over these series of presented results, and high resolution analytical microscopy emerges as a powerful tool in guiding high performance Si cell research.

In cloud storage applications where the data is shared by multiple mobile users, it is essential to provide the consistency among mobile users by means of appropriate synchronization algorithms. In particular, if the data is frequently updated and the number of mobile users sharing the data is large, the synchronization traffic can be significant. Moreover, the excessive synchronization traffic in mobile networks is more important in terms of radio resource utilization and energy consumption. In this paper, we propose an efficient delta synchronization (EDS) algorithm that aggregates the updated data to reduce the synchronization traffic and synchronizes the aggregated one periodically to satisfy the consistency. To find out the optimal policy for the aggregation and the periodical synchronization, an optimization problem is formulated as a Markov decision process (MDP) and a value iteration algorithm is presented for computing the stationary deterministic policy. Numerical results demonstrate that EDS can choose the optimal action that strikes a balance between the reduction of the synchronization traffic and the satisfaction of the consistency.

We investigate how SiOx oxide interlayers prepared by different techniques (chemical, thermal) in combination with hydrogen released from an ALD Al2O3 source layer govern passivation in 1) passivated contacts based on doped poly-Si layers and tunneling SiO2, and 2) wafer surface passivation by Al2O3. Profiles of O and H in these structures with engineered, buried SiOx interlayers were measured by Time-of-Flight SIMS (TOF-SIMS) at nanometer resolution. Passivated contacts perform best with thermally oxidized SiOx, while chemical SiOx causes poly-Si film blistering and performance degradation. ALD Al2O3 acts as passivating H source, significantly improving B-doped and intrinsic poly-Si contacts for IBC cells. Fast-diffusing hydrogen from the Al2O3 source layer appears to penetrate Si wafer thickness, improving the passivation of structures at the opposite side. In contrast to the passivated contacts, chemical SiOx interlayer promotes wafer surface passivation by ALD Al2O3, while similarly thin thermal SiO2 suppresses passivation and built-in charge.

We form gallium-doped poly-Si:Ga/SiO 2 passivated contacts on n-type Czochralski (n-Cz) wafers using ion implantation of Ga and Ga-containing spin-on dopants. After annealing and passivation with Al 2 O 3 , the contacts exhibit iVoc values of >730 mV with corresponding Joe values of <;5 fA/cm 2 . These are among the best-reported values for p-type poly-Si/SiO 2 contacts. Secondary ion mass spectroscopic depth profile data show that, in contrast to B, Ga does not pileup at the SiO 2 interface in agreement with its known high diffusivity in SiO 2 . This lack of Ga pileup may imply fewer dopant-related defects in the SiO 2 , compared with B dopants, and account for the excellent passivation.