Nathanaelle Schneider

Atomic layer deposition for nanomaterial synthesis and functionalization in energy technology

Atomic layer deposition (ALD) has been receiving more and more research attention in the past few decades, ascribed to its unrivaled capabilities in controlling material growth with atomic precision, manipulating novel nanostructures, tuning material composition, offering multiple choices in terms of crystallinity, and producing conformal and uniform film coverage, as well as its suitability for thermally sensitive substrates. These unique characteristics have made ALD an irreplaceable tool and research approach for numerous applications. In this review, we summarize the recent advances of ALD in several important areas including rechargeable secondary batteries, fuel cells, solar cells, and optoelectronics. With this review, we expect to exhibit ALDs versatile potential in providing unique solutions to various technical challenges and also hope to further expand ALDs applications in emerging areas.

Atomic layer deposition of zinc indium sulfide films: Mechanistic studies and evidence of surface exchange reactions and diffusion processes

The authors present the elaboration of zinc indium sulfide (ZnInxSy) thin films in the context of a cadmium-free buffer layer development for copper indium gallium diselenide photovoltaic solar cells. The films were deposited by atomic layer deposition (ALD) from ZnEt2 (DEZ), In(acac)3 (acac = acetylacetonate), and H2S at 200 °C. In situ growth kinetics studies were performed with the quartz crystal microbalance technique to determine the respective mass gain per cycle of ZnS and In2S3 layers, allowing determination of the atomic compositions of the ZnInxSy thin films to be expected if the deposition strictly follows the rule of mixtures. As the experimental atomic compositions of the ZnInxSy films differ significantly from this rule, a comprehensive study of the growth mechanism was performed to determine the nature of the side reactions. First, an exchange reaction between In2S3 and the Zn precursor was identified, though this process is not sufficient to account for the experimental data, and therefore...

Deposition of ultra thin CuInS2 absorber layers by ALD for thin film solar cells at low temperature (down to 150 ?C)

Two new processes for the atomic layer deposition of copper indium sulfide (CuInS₂) based on the use of two different sets of precursors are reported. Metal chloride precursors (CuCl, InCl₃) in combination with H2S imply relatively high deposition temperature (Tdep = 380 °C), and due to exchange reactions, CuInS₂ stoechiometry was only achieved by depositing In₂S3 layers on a CuxS film. However, the use of acac- metal precursors (Cu(acac)₂, In(acac)₃) allows the direct deposition of CuInS₂ at temperature as low as 150 °C, involving in situ copper-reduction, exchange reaction and diffusion processes. The morphology, crystallographic structure, chemical composition and optical band gap of thin films were investigated using scanning electronic microscope, x-ray diffraction under grazing incidence conditions, x-ray fluorescence, energy dispersive spectrometry, secondary ion mass spectrometry, x-ray photoelectron spectroscopy and UV-vis spectroscopy. Films were implemented as ultra-thin absorbers in a typical CIS-solar cell architecture and allowed conversion efficiencies up to 2.8%.

Synthesis of indium oxi-sulfide films by atomic layer deposition: The essential role of plasma enhancement.

Summary This paper describes the atomic layer deposition of In2(S,O)3 films by using In(acac)3 (acac = acetylacetonate), H2S and either H2O or O2 plasma as oxygen sources. First, the growth of pure In2S3 films was studied in order to better understand the influence of the oxygen pulses. X-Ray diffraction measurements, optical analysis and energy dispersive X-ray spectroscopy were performed to characterize the samples. When H2O was used as the oxygen source, the films have structural and optical properties, and the atomic composition of pure In2S3. No pure In2O3 films could be grown by using H2O or O2 plasma. However, In2(S,O)3 films could be successfully grown by using O2 plasma as oxygen source at a deposition temperature of T = 160 °C, because of an exchange reaction between S and O atoms. By adjusting the number of In2O3 growth cycles in relation to the number of In2S3 growth cycles, the optical band gap of the resulting thin films could be tuned.

Temperature effect during atomic layer deposition of zinc oxysulfide -Zn(O,S) buffer layers on Cu(In,Ga)(S,Se)2 synthesized by co-evaporation and electro-deposition techniques

In this study, we investigate the performances of Cu(In,Ga)(S,Se)2/Zn(O,S) devices varying both the absorber and the deposition temperature of the atomic layer deposited Zn(O,S) buffer layer. For both types of devices, two ranges of Zn(O,S) deposition temperatures were found to improve significantly the opto-electronic parameters, due to either specific Zn(O,S) properties or interdiffusion mechanisms. With this approach, we demonstrated the existence of two distinct favorable band alignments at the CIGS/Zn(O,S) junction. This study also demonstrates the benefits of using Atomic layer Deposition to accurately control the Zn(O,S) properties and therefore avoid device annealing and i-ZnO replacement by (Zn,Mg)O window layer.

Highly efficient MoOx-free semitransparent perovskite cell for 4 T tandem application improving the efficiency of commercially-available Al-BSF silicon

In this work, the fabrication of MoOx-free semitransparent perovskite solar cells (PSC) with Power Conversion Efficiencies (PCE) up to 15.7% is reported. Firstly, opaque PSCs up to 19.7% were fabricated. Then, the rear metal contact was replaced by a highly transparent and conductive indium tin oxide (ITO) film, directly sputtered onto the hole selective layer, without any protective layer between Spiro-OMeTAD and rear ITO. To the best of our knowledge, this corresponds to the most efficient buffer layer-free semitransparent PSC ever reported. Using time-resolved photoluminescence (TRPL) technique on both sides of the semitransparent PSC, Spiro-OMeTAD/perovskite and perovskite/TiO2 interfaces were compared, confirming the great quality of Spiro-OMeTAD/perovskite interface, even after damage-less ITO sputtering, where degradation phenomena result less important than for perovskite/TiO2 one. Finally, a 4-terminal tandem was built combining semitransparent PSC with a commercially-available Aluminium Back Surface Field (Al-BSF) silicon wafer. That silicon wafer presents PCE = 19.52% (18.53% after being reduced to cell size), and 5.75% once filtered, to generate an overall 4 T tandem efficiency of 21.18% in combination with our champion large semitransparent PSC of 15.43%. It means an absolute increase of 1.66% over the original silicon wafer efficiency and a 2.65% over the cut Si cell.