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We present results from the application of a novel, contactless patterning technique to form the doped fingers required for interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells. The technique involves patterning the RF powered electrode in a custom-designed RF-PECVD chamber. The patterned powered electrode – which has 1 mm wide opening-slits in it - is brought in close proximity to the substrate surface, to localize the plasma and the process it performs. In this work, the localized plasma process being employed is an NF3/Ar etching, and is used to form doped fingers that are sub-mm wide and 60 mm long. The interdigitated structure (alternating electron and hole collection zones) is created by first uniformly depositing an intrinsic/n-type a-Si:H passivation stack, followed by an n-type/p-type µc-Si:H recombination junction on the rear side. A passivation layer is also deposited on the front side. The regions for the hole collection zones are then etched down to the intrinsic a-Si:H layer, and finally, a uniform p-type a-Si:H layer is deposited everywhere. The etched finger areas are first investigated by profilometry and spectroscopic ellipsometry, showing that the process can be controlled to leave as little as a few nanometers of passivating intrinsic a-Si:H. This fine control is achieved by pulsing the plasma, to slow the etching rate to a few A/s. To evaluate the detailed opto-electronic properties of the structure, the samples are mapped out using two contactless techniques: Photoluminescence and Surface Photovoltage measurements (done with a macroscopic scanning Kelvin probe performed under dark and illuminated conditions). These measurements enable one to see both zones of degraded passivation, and the effectiveness of the doped regions in generating an open circuit voltage under illumination.

Silicon thin film technology has been driven by hydrogenated amorphous and microcrystalline silicon thin films which are routinely produced using silane plasmas. While SiH 3 is often considered as the main radical for the obtaining of such films, we have shown that changing the process to conditions where silicon clusters and nanocrystals are produced in the plasma can lead to high deposition rates and improved materials, such as hydrogenated polymorphous silicon and polycrystalline silicon [1]. Moreover, by changing the substrate from glass to crystalline silicon, it is possible to produce epitaxial crystalline silicon films (c-Si:H) which can be transferred to foreign substrates to make ultrathin crystalline silicon solar cells [2], [3]. Interestingly enough the structure of these films is found to be tetragonal, indicative of their particular growth process [4]. Even more interesting, this low temperature epitaxial process can be extended to doped films as well as to germanium and SiGe alloys and their heteroepitaxial growth on GaAs [5]. Last but not least, combining PECVD with low melting temperature metal nanoparticles such as indium and tin opens the way to the growth of nanowires (including Ge, Si and GeSn), which allow to achieve efficient light trapping and carrier collection in radial junction solar cells [6] or even to growth in-plane c-Si nanowires for stretchable electronics and photonics applications [7], [8].

Modulated Photoluminescence (MPL) is a powerful tool for measuring the minority carrier lifetime of solar cells. An in house in situ MPL equipped Plasma Enhanced Chemical Vapor Deposition reactor enables the monitoring of passivation properties of solar cells during the fabrication steps of devices. In this study, this tool was used to analyze the impact of annealing steps on passivation properties. First, samples passivated by an aluminum oxide layer were annealed and the evolution of the effective lifetime in the wafer was studied. This allowed to optimize the temperature and duration of the heat treatment. A similar study was made on Fired Passivating Contacts with a passivating stack of SiO x /(p) $\mu\mathrm{c}$ -Si:H/SiN x :H. An interesting low-lifetime regime is consistently observed when the samples undergo a high temperature ( $\mathrm{T} > 350^{\circ}\mathrm{C}$ ) annealing step, followed by a lifetime recovery during the subsequent cooling step. Corona charge and TEM images allowed to get a deeper understanding of the passivation mechanisms evidenced during in situ MPL measurements.

Blistering of Al2O3/SiNX:H stacks has been regularly reported over the last decade. Despite several studies, it has not been possible to link blistering density and lifetime degradation. In this work we demonstrate the use APiC technique to probe the c-Si/Al2O3 interface. It allows us to show that it might not be the delaminated surface fraction which rules the lifetime degradation but most likely the interface quality of non-delaminated areas. Blistering is the top of the iceberg; characterizing the interface with the high sensitivity provided by APiC is a breakthrough.

Texturing of crystalline silicon at the light wavelength scale is a promising approach for light management in ever thinner cells. However, this approach requires adapting the device design and process, which has so far revealed to be a challenging task. Indeed, successful integration requires compromising the excellent optical properties for preserving the electrical ones. We briefly summarize what has been learned so far in the community and illustrate some of these learnings with the fabrication and improvement of 1-μ m-thin monocrystalline nanotextured silicon solar cells.

Variation of the substrate temperature within the ALD window during deposition does not significantly impact the growth rate of Al 2 O 3 layers but changes their properties. Reduced initial deposition temperature allows storing hydrogen at the c-Si/ Al 2 0 3 interface. This hydrogen is steadily released during the deposition of upper layers due to the increase of substrate temperature. Al 2 0 3 can thus provide SRV

Based on recent advancements of radial junction silicon nanowire (RJ SiNWs) solar cells, a demonstration of $5\mathrm{x}5 \pmb{\mathrm{cm}^{2}}$ RJ $\mathbf{SiNW}$ solar mini-module is presented in this work. The $\mathbf{SiNW}$ devices were grown by plasma-assisted vapor-liquid-solid technique at low temperature in a plasma-enhanced chemical vapor deposition reactor. The $\pmb{5\mathrm{x}5\ \mathrm{cm}^{2}}$ mini-modules have been obtained using a commercial laser scribing apparatus. The laser scribing insures a monolithic integration of electrically separated cells. We have obtained a power generation of 10 $\mathbf{mW}$ from 5 individual cells of total active area of 8.6 $\pmb{\mathrm{cm}^{2}}$. The mini-module has an open-circuit voltage of 3.85 V. The performance was evaluated using solar simulator and short comings (high series resistance) were analyzed using a home-made electroluminescence setup.

Recent developments have unlocked the main issues arising from the combination of III-V and silicon and have opened a new way to fabricate tandem solar cells. We here propose to evaluate such tandem concept based on inverse metamorphic growth of c-Si(Ge) on GaAs by means of numerical simulation. Electrical and optical models are first faced to experimental realizations of single junction cells to calibrate material parameters and to assess the electrical quality of the epi-SiGe layer. Then the tandem structure is optimized, current matching conditions are given and the benefit of using a 2D grating at the back-side is studied.

The use of Kelvin Probe Force Microscopy to investigate PN junctions under illumination and electrical bias has been shown to be an effective way to analyze the electrical properties of solar cells at the nanoscale. We use it here, for the first time, on interdigitated back contact solar cells. Measurements are performed between the metallic fingers under an electrical bias in the dark and under illumination in open circuit conditions. Our results show that that KPFM could be used to identify and localize diodes resistance losses at the nanoscale.

Hydrogenated polymorphous silicon (pm-Si:H) is a material consisting of a small volume fraction of nanocrystals embedded in an amorphous matrix. pm-Si:H solar cells demonstrate interesting initial degradation behaviors such as rapid initial change in photovoltaic parameters and large macroscopic structural change during light-soaking. The precise dynamics of the light-induced degradation was studied in a series of light-soaking experiments. Complementary studies reveal that the initial degradation of pm-Si:H solar cells originate from the modification of silicon-hydrogen bonding on the surface of silicon nanocrystals in pm-Si:H.

This paper describes ongoing studies on the emitter formation by PECVD (Plasma Enhanced Chemical Vapor Deposition) using SiF4/H2/Ar chemistry in crystalline silicon solar cells. H2 depletion and ion bombardment have been highlighted to be crucial factors to sustain epitaxial growth. By controlling these parameters we have been able to produce a 2.5µm-thick high-quality silicon epitaxy and to define a process window. Structural properties were assessed by in-situ and exsitu spectroscopic ellipsometry as well by HR-TEM (High Resolution Transmission Electron Microscopy) images with the diffraction patterns. These studies have been extended to n-type and p-type doped layers.

The technical performance and robustness of the inverters used for connecting the PV modules to the network of electricity distribution are key elements which can have a significant effect on the production of electrical energy and therefore the financial viability of a power system. This work is a contribution to the modeling and control of a new structure for multilevel converters used in photovoltaic panels. This represents a new approach for photovoltaic panels where alternative current can be directly produced. In this paper, a functional model for the multilevel converters is presented; a knowledge model using connection functions of the switches and the half-arm is elaborated; a control model is proposed and several PWM multilevel control strategies are developed. The quality of the output signal of the current delivered by the multilevel inverter integrated with the photovoltaic panel is analyzed.

Efficient integration of III–V on silicon has been one of the most material science sought-after goal, for decades, since it can have huge impact on photonics, microelectronics and photovoltaic research and industry. Here we present an original approach where silicon is epitaxially grown on GaAs by low temperature plasma enhanced CVD. Without ultra-high vacuum and keeping temperature below 200°C, both GaAs surface cleaning and subsequent heteroepitaxial growth are achieved, and monitored by in-situ ellipsometry. Optical and TEM characterization reveal high crystal quality despite lattice mismatch. Single junction diodes are built to investigate interface electrical properties.

In this work, we address the doping dependence of SHJ solar cell precursor passivation degradation upon ITO sputtering by PVD. We report the higher apparent sensitivity of the emitter. By varying the doping, we were able to demonstrate that the emitter is not necessarily less resilient to this process. Indeed the same amount of defects can be created on the BSF side all the while remaining screened thanks to the highly effective field-effect provided by the capping n-doped a-Si:H layer.

Microcrystalline silicon deposited from SiF 4 /H 2 /Ar gas mixtures is used as active absorbing layer in thin film solar cells. Best solar cells are made from active layers deposited at the amorphous-to-microcrystalline transition where only a few percent of amorphous phase is present. Based on mass spectrometry measurements, we propose a simple model which accounts for the relevant features of the complex plasma chemistry: namely the depletion of H 2 , the formation of HF molecules and the amorphous to microcrystalline silicon transition. The specificity of SiF 4 /H 2 /Ar plasma is the ability to tightly tune the transition irrespective of the control of the deposition rate. A high crystalline fraction allows thicknesses above 3 µm with a high short-circuit current and no deterioration of the open-circuit voltage.

We propose a novel design using multi-resonant absorption to achieve efficient light-trapping in ultra-thin (

In this work, we report on the last investigations of (n+) a-Si:H / (p) c-Si heterojunction solar cells deposited by both HWCVD and PECVD. Regarding HWCVD films, we use spectroscopic ellipsometry measurements to characterize the material properties of the deposited films. Particularly, we study the effect of the (i) a-Si:H film on the (n+) a-Si:H film growth. As far as PECVD films are concerned, an optimum PH 3 flow is determined from the point of view of dark conductivity. Additionally, QSS-PC measurements are used to determine the improvement in the passivation quality of this film. Finally, HWCVD and PECVD HIT emitters are compared. A high quality in both emitters is deduced with implied Voc values exceeding 665 mV