As PV enters the terawatt era, reliability, sustainability and low carbon footprint of solar modules are key requirements. The N.I.C.E. TM technology from Apollon Solar is a good candidate for significant improvements in these areas. As the second-generation pilot line is now functional with IEC certification underway, we present a holistic assessment of N.I.C.E. TM technology compared with conventional module technology with encapsulant. This includes electrical performance and cost/consumables, reliability, and degradation mechanisms as well as sustainability aspects. In addition, the new generation of N.I.C.E.-wire modules are presented that use thin round Cu wires instead of flat ribbons for interconnection. This candidate technology for an alternative to the Smart Wire Connection Technology (SWCT) is investigated experimentally as well as via numerical simulations.

In this work, we integrate defect engineering methods of gettering and hydrogenation into silicon heterojunction solar cells fabricated using low‐lifetime commercial‐grade p‐type Czochralski‐grown monocrystalline and high‐performance multicrystalline wafers. We independently assess the impact of gettering on the removal of bulk impurities such as iron as well as the impact of hydrogenation on the passivation of grain boundaries and B‐O defects. Furthermore, we report for the first time the susceptibility of heterojunction devices to light‐ and elevated temperature–induced degradation and investigate the onset of such degradation during device fabrication. Lastly, we demonstrate solar cells with independently verified 1‐sun open‐circuit voltages of 707 and 702 mV on monocrystalline and multicrystalline silicon wafers, respectively, with a starting bulk minority‐carrier lifetime below 40 microseconds. These remarkably high open‐circuit voltages reveal the potential of inexpensive low‐lifetime p‐type silicon wafers for making devices with efficiencies without needing to shift towards n‐type substrates.

Czochralski (Cz)‐grown upgraded metallurgical‐grade (UMG) silicon wafers degrade significantly during high‐temperature processes, eroding their appeal as a low‐cost alternative to conventional electronic‐grade silicon wafers. However, the thermal degradation in UMG wafers can be delayed by utilizing a prefabrication annealing step. Based on this, a high‐efficiency solar‐cell process is modified by selecting a single‐boron diffusion step and applying phosphorus‐doped polycrystalline films as electron‐selective contacts with excellent impurity‐gettering properties to minimize the thermal budget. The application of this modified high‐efficiency solar‐cell process to n‐type UMG‐Cz wafers results in a solar cell with a conversion efficiency of 22.6% on a cell area of 2 × 2 cm2.

One promising PV module technology in terms of reducing expensive consumables while keeping the performance on a high level is the N.I.C.E.(TM) (New Industrial Solar Cell Encapsulation) module technology from Apollon Solar that is based on mechanical pressing contacts. In this paper, we investigate the question if the N.I.C.E.(TM) module technology is well suited for temperature-sensitive silicon heterojunction (SHJ) solar cells. We present challenges encountered during the ramp-up of our lab-scale manufacturing from 1x1 to 3x4 modules. In the experimental study, we used SHJ cells with different front metal pastes and could demonstrate the high performance of N.I.C.E.(TM) technology irrespective of the type of paste. Record aperture area module efficiencies of 20.6% are achieved and the LIV parameters are modeled via SunSolve (TM) simulations. We derive from our investigations that this eco-friendly, recyclable technology is well competitive to standard laminate-based module technology.

Pre‐fabrication gettering and bulk hydrogenation processes are applied to low‐bulk‐lifetime (25 μs) p‐type Czochralski silicon wafers before silicon heterojunction (SHJ) solar cell fabrication, resulting in effective minority carrier lifetime enhancements by a factor of six. On complete SHJ solar cells, this translates to an improvement in the open‐circuit voltage ( V OC ) of 71 mV, resulting in V OC values as high as 692 mV. This remarkably high V OC suggests that efficiencies approaching 25% could be possible for low‐cost p‐type Czochralski silicon wafers – not the typical expensive, high‐quality n‐type ones with lifetimes of several milliseconds – in the near future. This method is also likely applicable to n‐type SHJ solar cells to reduce the incoming wafer lifetime requirements and to other silicon solar cell structures featuring passivated contacts.

Silicon heterojunction solar cells are primarily fabricated with high-quality wafers, resulting in a higher manufacturing cost than mainstream solar cells. We explore the impact of defect engineering methods of hydrogenation and gettering into silicon heterojunction solar cells fabricated using low-lifetime, commercial-grade, p-type, Czochralski-grown monocrystalline and high-performance multicrystalline wafers. We demonstrate solar cells with independently verified open-circuit voltages of 707 mV and 702 mV on monocrystalline and multicrystalline silicon wafers, respectively, thus exceeding 700 mV on multicrystalline silicon materials for the first time in the world. These remarkably high open-circuit voltages reveal the potential of cost-competitive low-quality p-type silicon wafers for making high-efficiency solar cells with efficiencies without the need of shifting towards expensive, high-quality wafers.

This paper investigates the potential of three different methods—tabula rasa (TR), phosphorus diffusion gettering (PDG), and hydrogenation, for improving the carrier lifetime in n-type Czochralski-grown upgraded metallurgical-grade (UMG) silicon samples. Our results show that the lifetimes in the UMG wafers used in this study were affected by both mobile metallic impurities and as-grown oxygen precipitate nuclei. Thus, the dissolution of grown-in oxygen precipitate nuclei via TR and the removal of mobile impurities via PDG step were found to significantly improve the electronic quality of the UMG wafers. Finally, we report bulk lifetimes and 1-sun implied open-circuit voltages of the UMG wafers after boron and phosphorus diffusions, as typically applied in n-type cell fabrication.

In difference to laminated state-of-the-art PV modules, major components of Apollon Solar's proprietary NICE (`New Industrial Cell Encapsulation') modules are not physically attached to each other due to the absence of soldering and lamination. This allows for an efficient and low-cost disassembly of end of life NICE modules into their original components, such as glasses, copper connectors, solar cells. The fact that these components can be recovered as entire pieces opens up a more sustainable and high value recycling and reuse potential, in terms of waste management towards a circular economy. This work reports results from feasibility studies on the disassembly of NICE modules and recycling/reuse of their components, carried out in the frame of the European H2020FOF-13-2015 `ECOSOLAR' project.

This paper investigates the impact of tabula rasa (TR) and phosphorus diffusion gettering (PDG), both in isolation and in combination, for improving the electronic quality of n-type Czochralski grown Upgraded Metallurgical-Grade (UMG) silicon wafers. We have found that the bulk lifetimes of the UMG wafers were affected by both oxygen precipitate nuclei and mobile metallic impurities. Thus, we achieved the best bulk lifetimes after subjecting the UMG wafers to a TR step prior to a PDG step. Further, we report silicon heterojunction solar cells results based on the UMG wafers subjected to a TR step prior to a PDG step. The best in-house measured efficiencies were 21.2 % and 20.8 % for the UMG wafers from the middle and tail regions of the ingot, respectively.

1School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Kensington, NSW, 2052, Australia 2School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706, USA 3Department of Engineering, Information Sciences and Engineering Institute, The Australian National University, Canberra ACT 0200, Australia 4Apollon Solar, Charlemagne, Lyon, 69002, France E-mail: Daniel.chen@unsw.edu.au

In this work the first All Copper NICE (New Industrial Solar Cell Encapsulation) modules with solder-free ribbon to finger interconnections are presented. Experiments were conducted to investigate if silver can be fully omitted from solar cells with copper plated fingers in combination with the NICE module technology. We could show that silver flash plating, front and rear silver busbars or pads can be omitted without compromising series resistance or module performance. All Copper NICE modules were manufactured with fillfactors up to 76.8 %.

This conference paper deals on one hand with the monitoring of the current degrees of achievement of the targets of the European H2020-FOF-13-2015 Eco-Solar project regarding project targets in material reduction. On the other hand the environmental impacts like carbon footprint, acidification or resource depletion of the current processing status of the individual work packages are considered in relation to the environmental impacts of the manufacturing processes of state of the art PV modules (baseline). In the halftime assessment, by implementing all previous project developments into the production process chain (ingot  wafer  cell  module) the project target reduction demand of aluminium can be achieved totally for both, monoand multi-Si based PV modules, the project target reduction demand of argon gas can be achieved totally for mono-Si based PV modules only. Most of the other project targets benefit as well, but without achieving the target values yet. Compared to the results of state of the art PV modules (baseline) environmental advantages exist for almost all examined impact categories. The only exception is eutrophication terrestrial of the improved production process of multi-Si based PV modules. In the case of climate change, the greenhouse emissions are reduced by more than 11 % for mono-Si based PV modules and more than 15 % for multi-Si based PV modules. The improvements trace back to the ingot production as well as module production mainly and to a lower proportion to the wafer production.

Our simulation work aims at analyzing optical loss mechanisms for two types of glass-glass modules: laminated modules, using for example EVA (ethylene vinyl acetate) as encapsulant, and modules without encapsulant that are filled with neutral gas. The simulation results give arguments in favor of the use of gas as encapsulant in glass-glass PV modules instead EVA. Indeed, with an anti-reflection coating (ARC) on both sides of the front glass of the module and an appropriate ARC on the cell, the collected current of a cell encapsulated with gas is almost equal than the one obtained for a standard EVA module with a single side ARC on the glass and an appropriate ARC on the cell under an AM1.5G spectrum. Because of the different spectral behavior of the two materials, a careful filtering of lamps used in solar simulators is mandatory due to the high-infrared content, in order to compare gas filled modules to EVA laminated ones. Low UV content in the incident spectrum underestimates the optical losses in the EVA module and high-infrared content overestimates the optical losses in the gas filled module. This analysis shows that the refractive index of SiN of industrial solar cells and the current spectral distribution of solar simulators defined according to the norm IEC 60904-9 could penalize gas filled modules in comparison to EVA laminated ones. (C) 2017 The Authors. Published by Elsevier Ltd.

In this paper, we present the 3D simulation of>20% efficiency solar cells using n-type 100% Upgraded-Metallurgical Grade (UMG) Czochralski (CZ) silicon and Electronic Grade (EG) Float Zone (FZ) fabricated using the same process. The cells have a passivated emitter rear locally diffused (PERL) structure, with an etch-back approach on the rear to maintain high bulk lifetime in the cells via phosphorus gettering. Simulation ofthe power losses of both devices are analysed as a function of measured material and cell parameters, including minority carrier lifetime, reflectance, contact resistivity and recombination parameters of the diffused and non-diffused surfaces.

We present solar cells fabricated with n-type Czochralski–silicon wafers grown with strongly compensated 100% upgraded metallurgical-grade feedstock, with efficiencies above 20%. The cells have a passivated boron-diffused front surface, and a rear locally phosphorus-diffused structure fabricated using an etch-back process. The local heavy phosphorus diffusion on the rear helps to maintain a high bulk lifetime in the substrates via phosphorus gettering, whilst also reducing recombination under the rear-side metal contacts. The independently measured results yield a peak efficiency of 20.9% for the best upgraded metallurgical-grade silicon cell and 21.9% for a control device made with electronic-grade float-zone silicon. The presence of boron-oxygen related defects in the cells is also investigated, and we confirm that these defects can be partially deactivated permanently by annealing under illumination.

We present n-type Czochralski-grown silicon solar cells made from 100% upgraded metallurgical grade silicon feedstock, with an independently certified peak efficiency of 21.1%. We look at the impact of net doping and minority carrier lifetime and mobility on the short-circuit current and the open-circuit voltage.

The European H2020-FOF-13-2015 Eco-Solar project, that started in October 2015 envisions to increase resource and energy efficiency over the entire photovoltaic value chain, while simultaneously maximising recycling and remanufacturing possibilities, by introducing design for recovery, repair and reuse, and collaborating for improvements in waste reduction. Reusing materials and reducing the consumption of raw materials will make solar cell panels both cheaper and greener. When fewer resources, including critical materials are needed, the emissions of greenhouse gases from their production will decrease. Likewise, the energy consumed by these processes will be paid off faster than it is today. All this should improve market penetration for European PV producers. The overarching aim is to strengthen European PV companies who are driven by innovation and who are able to secure Europe’s power supply in a sustainable way. The paper presents the methodology followed by EcoSolar to reach this ambitious goal.

The recombination parameters of aluminium–oxygen complexes in silicon have been reassessed by applying lifetime spectroscopy on several n‐ and p‐type intentionally Al‐contaminated and control samples, using a single‐level defect model. The presence of the control samples has allowed greater accuracy for the extraction of the recombination lifetime. The uncertainty ranges of the parameters have been tightened significantly by simultaneously fitting the lifetime on several samples. The electron/hole capture cross section ratio k was reassessed to be 380, in the uncertainty range of 330–460. A direct comparison of the n‐ and p‐type samples has shown that those complexes are much more recombination‐active in p‐type silicon than in n‐type silicon at low and intermediate injection levels.