Precursor Layer Research Articles

Evolution of nanodiamond seeds during the chemical vapor deposition of diamond on silicon substrates in oxygen-rich plasmas

Methane, oxygen and hydrogen in relative concentrations of 1:0.5:98.5 were employed to deposit diamond films by microwave plasma enhanced chemical vapor deposition on Si(001) substrates seeded with detonation nanodiamonds of 5⋅1010cm−2 density. The interaction between the nanodiamonds and the plasma was investigated as a function of the chamber pressure and the substrate temperature. At 40 Torr and 935°C, 90% of the seeds were etched, and growth induction occurred with an impractically long time of 23.5 h. Varying the substrate temperature between 827°C and 935°C did not lead to faster growth induction. Reducing the chamber pressure to 30 Torr instead resulted in continuous films with induction time as short as 12 min. The induction time and the growth rate exhibited an Arrhenius dependence in the temperature range 769–884°C with apparent activation energies of 3.7 eV/atom and 0.3 eV/atom, respectively. When at 30 Torr the concentration of the oxygen additive was raised to 1 vol%, the seeds were completely dissolved and no film deposition took place. However, film growth was possible with an oxygen admixture as high as 1.5 vol% on a diamond precursor layer of approximately 55 nm thickness, which was nucleated in an oxygen-free plasma.

Vapor-Phase Processing of Metal-Organic Frameworks.

ConspectusPorous metal-organic frameworks (MOFs), formed from organic linkers and metal nodes, have attracted intense research attention. Because of their high specific surface areas, uniform and adjustable pore sizes, and versatile physicochemical properties, MOFs have shown disruptive potential in adsorption, catalysis, separation, etc. For many of these applications, MOFs are synthesized solvothermally as bulk powders and subsequently shaped as pellets or extrudates. Other applications, such as membrane separations and (opto)electronics, require the implementation of MOFs as (patterned) thin films. Most thin-film formation methods are adapted from liquid-phase synthesis protocols. Precursor transport and nucleation are difficult to control in these cases, often leading to particle formation in solution. Moreover, the use of solvents gives rise to environmental and safety challenges, incompatibility issues with some substrates, and corrosion issues in the case of dissolved metal salts. In contrast, vapor-phase processing methods have the merits of environmental friendliness, control over thickness and conformality, scalability in production, and high compatibility with other workflows.In this Account, we outline some of our efforts and related studies in the development and application of vapor-phase processing of crystalline MOF materials (MOF-VPP). We first highlight the advances and mechanisms in the vapor-phase deposition of MOFs (MOF-VPD), mainly focusing on the reactions between a linker vapor and a metal-containing precursor layer. The characteristics of the obtained MOFs (thickness, porosity, crystallographic phase, orientation, etc.) and the correlation of these properties with the deposition parameters (precursors, temperatures, humidity, post-treatments, etc.) are discussed. Some in situ characterization methods that contributed to a fundamental understanding of the involved mechanisms are included in the discussion. Second, four vapor-phase postsynthetic functionalization (PSF) methods are summarized: linker exchange, guest loading, linker grafting, and metalation. These approaches eliminate potential solubility issues and enable fast diffusion of reactants and guests as well as a high loading or degree of exchange. Vapor-phase PSF provides a platform to modify the MOF porosity or even introduce new functionalities (e.g., luminescence photoswitching and catalytic activity). Third, since vapor-phase processing methods enable the integration of MOF film deposition into a (micro)fabrication workflow, they facilitate a range of applications with improved performance (low-k dielectrics, sensors, membrane separations, etc.). Finally, we provide a discussion on the limitations, challenges, and further opportunities for MOF-VPP. Through the discussion and analysis of the vapor-phase processing strategies as well as the underlying mechanisms in this Account, we hope to contribute to the development of the controllable synthesis, functionalization, and application of MOFs and related materials.

Transparent back‐junction control in Cu(In,Ga)Se2 absorber for high‐efficiency, color‐neutral, and semitransparent solar module

AbstractTransparent oxide back contact of Cu(In,Ga)Se2 (CIGS) solar cells is crucial for semitransparent or bifacial CIGS photovoltaics. Parasitic GaOx resistive layer formed at the back junction, however, has been the bottleneck for transparent photovoltaic applications. Here, we show that a complementary control of the back junction enabled a high efficiency, semitransparent CIGS module. By employing a thin Ag precursor layer prior to CIGS evaporation, the back‐junction barrier could be eliminated. Atomic probe tomography measurement suggests that an appreciable amount of Ag doping in the GaOx may form hole‐tunneling channels at the back junction. We also found that potassium fluoride (KF) post‐deposition treatment (PDT) increased the back‐junction resistance and the bulk CIGS resistance compared to the case with Na PDT. The KF‐induced increased resistances turned out to be beneficial for suppressing the parasitic shunt current along the P1‐scribing region in our CIGS solar module. Interestingly, J–V rollover caused by the KF‐induced back‐junction barrier completely vanished after see‐through laser scribing of the module. We attribute the barrier‐lowering to a laser‐induced local heating at the back junction. The complementary engineering strategy introduced here would allow functional oxide back contact in CIGS photovoltaic modules for both high efficiency and semi‐transparency.

Сoating of a multicomponent system Al–Cr–Ni–Co–Fe on a steel substrate obtained by laser

In recent years, the unique physical and mechanical properties of high-entropy alloys (HEAs) have been the subject of increased attention of researchers. The study of the thermodynamic characteristics of such materials may be of interest for formulating the principles of the formation of structures with the required functional characteristics. Since the processes of structure and phase formation, as well as the diffusion mobility of atoms, the mechanism for the formation of mechanical properties and thermal stability differ significantly from similar processes in traditional alloys, HEAs are singled out into a special group of materials.The article presents a brief overview of the results of obtaining a high-entropy alloy by the combined method. At the first stage, a precursor layer was deposited by сold gas dynamic spraying (CGDS), and at the second stage, it was subjected to high-energy action using a laser. An alloy of the Al-Cr-Ni-Co-Fe type has been studied. By varying the ratio of the components, it was possible to obtain an almost equimolar composition for this system. A prediction of properties and structure is made based on the phase composition of the system.

Efficiency improvement of electrodeposition-processed Cu(In,Ga)Se2 solar cell with widen surface bandgap by spin-coating In2S3 thin film

The Cu(In,Ga)Se2 (CIGSe) -based solar cell is a promising candidate in the photovoltaic market due to its excellent performance. It was reported that the surface bandgap of CIGSe is crucial to improve the device properties. However, in the post-selenization process of precursor layers, Ga tends to accumulate at the back contact leading to a narrow surface bandgap. In this work, the surface bandgap of CIGSe film was successfully widened by a spin-coating In2S3 thin film on the CIGSe surface. After annealing treatment of the CIGSe/In2S3 stack, sulfur incorporates into the absorber layer and a Cu-poor surface composition is formed. Thus, a surface inversion of CIGSe from p-type to n-type occurs leading to formation of a buried homojunction. The effect of different In2S3 thicknesses on device performance were investigated. A champion efficiency of 12.88 % for CIGSe solar cell was obtained with 40 nm In2S3 compared to 10.03 % for the reference device without In2S3. However, the performance of CIGSe solar cells were deteriorated with In2S3 film thicknesses over 40 nm. These results demonstrate that a suitable In2S3 film thickness is significant to increase the surface bandgap and promote the efficiency.

Effect of copper precursor layer thickness on the properties of preferentially oriented Cu4SnS4 thin films for photovoltaic applications

Copper tin sulfide (Cu–Sn–S) thin films have gathered great attention in the research for earth-abundant, non-toxic, and low-cost thin film solar cells. In this investigation, preferentially oriented Cu 4 SnS 4 thin films have been fabricated via a combination of chemical bath deposition and thermal evaporation for the first time. Stacked precursor layers of thermally evaporated copper and chemically deposited SnS thin films were annealed in the sulfur atmosphere at a temperature of 823 K for 1 h. The copper layer thickness was varied from 150 to 200 nm. Various characterization techniques were employed to study the structure, morphology, optical and electrical properties of the Cu 4 SnS 4 films (XRD, Raman, FE-SEM, AFM, UV–Vis spectroscopy) formed at different conditions. The orthorhombic structured films formed at the best conditions showed highly oriented growth along (102) plane. An intense peak at 316 cm −1 in the Raman spectrum further confirmed the formation of the Cu 4 SnS 4 phase. The crystalline sizes and bandgap energies of deposited films varied between 33.6 and 52.7 nm and 1.0–1.6 eV, respectively. The sample with a copper precursor layer thickness of 185 nm exhibited an optimum bandgap of 1.4 eV and larger grains implies that a copper layer of 185 nm in thickness on 200 nm SnS is an optimal precursor layer thickness for achieving highly oriented Cu 4 SnS 4 thin film with excellent properties. • First attempt to fabricate Cu 4 SnS 4 thin films via a combination of physical-chemical deposition methods. • Cu 4 SnS 4 thin films with novel preferential orientation along (102) plane. • Optimization of copper precursor layer thickness resulted enhanced crystallinity. • The optimum bandgap of 1.4 eV for photovoltaic applications.

A fluid-supported 3D hydrogel bioprinting method

Hydrogels are used in many biomedical applications, including regenerative medicine and surgical training phantoms. However, the ability to shape these materials into complex anatomical structures using additive manufacturing is limited in part by their low mechanical stiffness. We developed a hydrogel 3D printer, that projects patterns directly onto a thin layer of fluid-supported hydrogel precursor, which serves as a floating, liquid projection screen. This approach avoids inadvertent adhesion that affects typical resin-based 3D printers, and enables fast, continuous printing. As a consequence, we can print smooth objects free of layering artifacts, at rates of 200 mm/h along the Z-axis. We demonstrate the versatility of our approach by printing various complex structures, including free-standing channel networks with 500 μm-thick walls, using hydrogels with a wide range of stiffness from 7 kPa to more than 4 MPa. Lastly, because the printer features a free surface, we combined it with an extruder to perform multi-material printing. We use this strategy to create centimeter-scale, cell-laden hydrogels containing channels, that help address the key nutrient supply problem in bioprinting.

High-performance CuS/n-Si heterojunction photodetectors prepared by e-beam evaporation of Cu films as precursor layers

Transition metal dichalcogenides (TMDCs) are considered to be the most promising next-generation materials for electronics and optoelectronics due to their excellent properties. In this work, well-performing CuS films were prepared by e-beam evaporation of Cu films as precursor layers. Ag/n-Si/Al2O3/CuS/ITO heterojunction photodetector with high responsivity (0.41 A·W−1), detectivity (1.739 × 1011 Jones) and fast response speed (17 μs) at zero bias were prepared by optimising sulphuration temperature and using silicon wafers with inverted pyramid light-trapping structures as substrates. Besides, the photodetector exhibited excellent light absorption ability, with an EQE of 51.91% at 980 nm. All these results demonstrated that excellent photodetector materials can be obtained by using metal films as precursor layers, which provides novel ideas and methods for the synthesis of TMDCs materials.

Study on the construction of polyethyleneimine/nano-silica multilayer film on the carbon fiber surfaces to improve the interfacial properties of carbon fiber/epoxy composites

ABSTRACT To enhance the interfacial properties of carbon fiber (CF) reinforced epoxy composites without damaging the CF strength. The polydopamine (PDA) was used as the precursor layer, and polyethyleneimine (PEI) and nano-silica (nano-SiO2) were deposited on the surface of CF by layer-by-layer electrostatic self-assembly. The layered strengthening materials (CF-Ln) were prepared and the microstructure of the CF was systematically characterized. The results showed that when the number of self-assembled layers is 5 (CF-L5), nano-SiO2 covers the surface of CF uniformly, and the tensile strength of CF-L5 monofilament reaches the maximum value, which is 12.1% higher than that of untreated CF (U-CF). Meanwhile, the interface properties between CF-L5 and epoxy matrix have been significantly improved. The interfacial shear strength (IFSS) between CF-L5 and epoxy matrix is 99.4% higher than that of U-CF. The improvement of the interfacial properties between CF-L5 and epoxy matrix is due to the introduction of alarge number of active groups (-NH2, -OH) in the PEI/SiO2 multilayer film deposited on the surface of CF, which improves the wettability between the CF and epoxy matrix. Also, the nano-SiO2 increases the roughness of the CF surface and improves the mechanical engagement between the CF and epoxy resin.

Synthesis and photoelectric properties of SnSe films through selenization of evaporated Sn-metal films

Sn precursor layer was evaporated on a glass substrate by an electron-beam evaporation method and followed by selenization using Se powder. SnSe film was successfully prepared by adjusting the selenization temperature and selenization time. The phase, microstructure and optical properties of the SnSe films were studied by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy, and UV-Vis-NIR spectrophotometer. The results demonstrated that the pure phase polycrystalline SnSe films with a band gap of 0.93 eV could be prepared by selenizing at 450[Formula: see text]C for 60 min. Under the irradiation of a 980 nm laser with a power of 2 mW/cm2, photoelectric response characteristics of the SnSe films were tested, and the response time and recovery time of the prepared film were 62 ms and 80 ms, respectively, indicating that the SnSe film had a large application prospect in near-infrared light detection.

Fast Optical Reflectance Measurements during Spin Coating and Annealing of Organic–Inorganic Perovskite Precursor Solutions

In article number 2000479, Jörg Rappich and co-workers address early stages of film formation and crystallization of organic lead triiodide perovskites by employing in-situ high-speed spectral reflectance measurements. The time scale ranges from 0.2 milliseconds to seconds. Data were taken during spincoating and subsequent low-temperature annealing. The measurements enable the investigation of changes in the solution of the spin-coating process. The evaporation of the solvent during spin-coating results in the spontaneous crystallization of the perovskite layer. During the subsequent annealing process, the diffuse reflectance measured with high sensitivity provides insight into the transformation and crystallization process of the precursor layer to the final perovskite layer.

Unified Model for Laser Doping of Silicon from Precursors.

Laser doping of silicon with the help of precursors is well established in photovoltaics. Upon illumination with the constant or pulsed laser beam, the silicon melts and doping atoms from the doping precursor diffuse into the melted silicon. With the proper laser parameters, after resolidification, the silicon is doped without any lattice defects. Depending on laser energy and on the kind of precursor, the precursor either melts or evaporates during the laser process. For high enough laser energies, even parts of the silicon’s surface evaporate. Here, we present a unified model and simulation program, which considers all these cases. We exemplify our model with experiments and simulations of laser doping from a boron oxide precursor layer. In contrast to previous models, we are able to predict not only the width and depth of the patterns on the deformed silicon surface but also the doping profiles over a wide range of laser energies. In addition, we also show that the diffusion of the boron atoms in the molten Si is boosted by a thermally induced convection in the silicon melt: the Gaussian intensity distribution of the laser beam increases the temperature-gradient-induced surface tension gradient, causing the molten Si to circulate by Marangoni convection. Laser pulse energy densities above H > 2.8 J/cm2 lead not only to evaporation of the precursor, but also to a partial evaporation of the molten silicon. Without considering the evaporation of Si, it is not possible to correctly predict the doping profiles for high laser energies. About 50% of the evaporated materials recondense and resolidify on the wafer surface. The recondensed material from each laser pulse forms a dopant source for the subsequent laser pulses.

One-step CZT electroplating from alkaline solution on flexible Mo foil for CZTS absorber

In this work, Cu-Zn-Sn (CZT) is co-electrodeposited onto a flexible Mo substrate exploiting an alkaline bath (pH 10). The plating solution is studied by cyclic voltammetry, highlighting the effects of potassium pyrophosphate (K4P2O7) and EDTA-Na2 on the electrochemical behavior and stability of the metallic ionic species. The optimized synthesis results in a homogeneous precursor layer, with composition Cu 44 ± 2 at. %, Zn 28 ± 1 at. %, and Sn 28 ± 2 at. %. Soft and reactive annealing are employed respectively to promote intermetallic phase formation and sulfurization of the precursor to obtain CZTS. Microstructural (XRD, Raman), morphological (SEM), and compositional (EDX, XRF) characterization is carried out on CZT and CZTS films, showing a minor presence of secondary phases. Finally, photo-assisted water splitting tests are performed considering a CZTS/CdS/Pt photoelectrode, showing a photocurrent density of 1.01 mA cm−2 at 0 V vs. RHE under 1 sun illumination.Graphical abstract

Vanadium nitride@carbon nanowires with inner porous structure for high-efficient microwave absorption

Herein, N-doped carbon coated vanadium nitride nanowires (VN@NC NWs) with inner porous structure were synthesized by coating a thin layer of a carbon precursor of polydopamine (PDA) on ultralong V2O5 NWs followed by nitridation. The amorphous carbon coating could ensure the one-dimensional (1D) structure, as well as produce the inner pores during nitriding progress. The formational 1D porous architecture, high-crystallized VN nanoparticles and homogeneous N-doped carbon coating synergistically improved the materials' impedance match and thus enhanced their microwave absorption performances. The minimum reflection loss (RLmin) of the optimal samples/paraffin hybrid with 20 wt% was −60.2 dB with an effective absorption bandwidth (EAB, RL < −10 dB) of 3.8 GHz at a thickness of 2.75 mm, and its maximal EAB of 5.8 GHz with a RLmin of −49.8 dB at a thickness of 2.25 mm. Hence, the inner porous VN@NC NWs in this case would be as a high-efficient microwave absorber.

Photoelectrocatalytic degradation of glyphosate on titanium dioxide synthesized by sol-gel/spin-coating on boron doped diamond (TiO2/BDD) as a photoanode

The construction of a photoanode with several layers of titanium oxysulfate as a precursor to form titanium dioxide-TiO2 on boron doped diamond-BDD (TiO2/BDD), and its application for the photoelectro-degradation of glyphosate in aqueous medium are presented. The study was divided into three stages: i) optimization of the number of layers of the TiO2 precursor to modify BDD using a novel method combining Sol-gel/Spin-Coating; ii) characterization of the TiO2/BDD electrodes, by scanning electron microscopy-SEM, dispersive energy spectroscopy-EDX, Ray diffraction-XRD, contact angle, and electrochemical response by cyclic voltammetry using [Fe(CN)6]3-/4- system; iii) degradation of glyphosate (50 mg L−1) by electrochemical oxidation on BDD and photoelectrocatalysis on TiO2/BDD in dark and UV-light conditions, at different current densities, for 5 h. The glyphosate degradation and mineralization were evaluated by High-Performance Liquid Chromatography, Total Organic Carbon, Chemical Oxygen Demand and inorganic-ions concentration (NO3−, PO43−, and NH4+). Also, the aminomethylphosphonic acid-AMPA was quantified by HPLC, as a degradation intermediate. Using five layers of the TiO2 precursor, in the construction of TiO2/BDD photoanode, and a lower contact angle, greater photoelectrocatalysis against the [Fe(CN)6]3-/4- redox system and better degradation of glyphosate compared to BDD without modification were achieved. The formation of TiO2 nanoparticles (14.79 ± 3.43 nm) in anatase phase on BDD was verified by SEM and XRD. Additionally, glyphosate degradation and mineralization were 2.3 times faster by photoelectrocatalysis on TiO2/BDD, relative to BDD, at 3 mA cm−2 and UV-light. Thus, the presence of TiO2 on BDD increases the rate and efficiency of glyphosate degradation with respect to electrochemical oxidation on BDD.

Investigation of Thermal Stability Effects of Thick Hydrogenated Amorphous Silicon Precursor Layers for Liquid‐Phase Crystallized Silicon

The thermal stability of thick (≈4 μm) plasma‐grown hydrogenated amorphous silicon (a‐Si:H) layers on glass upon application of a rather rapid annealing step is investigated. Such films are of interest as precursor layers for laser liquid‐phase crystallized silicon solar cells. However, at least half‐day annealing at T ≈550 °C is considered to be necessary so far to reduce the hydrogen (H) content and thus avoid blistering and peeling during the crystallization process due to H. By varying the deposition conditions of a‐Si:H, layers of rather different thermal stability are fabricated. Changes in the surface morphology of these a‐Si:H layers are investigated using scanning electron microscopy and profilometry measurements. Hydrogen effusion, secondary‐ion mass spectrometry (SIMS) depth profiling, and Raman spectroscopy measurements are also carried out. In summary, amorphous silicon precursor layers are fabricated that can be heated within 30 min to a temperature of 550 °C without peeling and major surface morphological changes. Successful laser liquid‐phase crystallization of such material is demonstrated. The physical nature of a‐Si:H material stability/instability upon application of rapid heating is studied.

Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se2 Thin‐Film Solar Cells Grown at Very Low Temperature

Achieving high power conversion efficiencies with Cu(In,Ga)Se2 (CIGS) solar cells grown at low temperature is challenging because of insufficient thermal energy for grain growth and defect annihilation, resulting in poor crystallinity, higher defect concentration, and degraded device performance. Herein, the possibilities for high‐performing devices produced at very low temperatures (≤450 °C) are explored. By alloying CIGS with Ag by the precursor layer method, (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells grown at about 450 °C reach an efficiency of 20.1%. Only a small efficiency degradation (0.5% and 1.6% absolute) is observed for ACIGS absorbers deposited at 60 and 110 °C lower substrate temperature. CIGS devices exhibit a stronger efficiency degradation, driven by a decrease in the open‐circuit voltage (). The root cause of the difference between ACIGS and CIGS devices is investigated by advanced characterization techniques, which show improved morphology, reduced tail states, and higher doping density in ACIGS absorbers. The proposed approach offers several benefits in view of depositions on temperature‐sensitive substrates. Increased Cu diffusion promoted by Ag allows end‐point detection in the three‐stage process at the substrate temperatures below 300 °C. The modified process requires minimal modification of existing processes and equipment and shows the potential for the use of different flexible substrates and device architectures.

Ambient Inkjet‐Printed High‐Efficiency Perovskite Solar Cells: Manipulating the Spreading and Crystallization Behaviors of Picoliter Perovskite Droplets

Drop‐on‐demand inkjet‐printing has the advantages of high cost‐effectiveness and powerful patterning ability, which can be a promising technique for perovskite pattern deposition. However, by far most of the reported works using inkjet‐printing for perovskite films fabrication are printing solvent‐rich wet precursor layers on the high‐temperature meso‐TiO2 substrate, and subsequently require a vacuum‐assisted thermal annealing process to enhance the crystallization of perovskite precursor, which largely elevates fabrication cost and process complexity. Herein, a heat‐assisted inkjet‐printing process is developed to directly print compact and uniform crystalline perovskite films on the planar PEDOT:PSS substrate under ambient condition. The effects of precursor composition, printing temperature, solvent system, and, especially, the printing parameters on the final morphology and microstructure of the printed perovskite films are systematically studied for the first time and the related crystal growth models are revealed, which provide a constructive guidance for the future studies on ambient inkjet‐printed perovskite films and devices. Based on these studies, a champion power conversion efficiency (PCE) of 16.6% for the ambient printed PSC devices is achieved. This work provides a reliable and cost‐effective approach for the scalable fabrication of perovskite films with a low material consumption.

Achieving stable anionic redox chemistry in Li-excess O2-type layered oxide cathode via chemical ion-exchange strategy

Triggering oxygen redox activity has been regarded as a promising strategy to boost the output capacity of cathode materials for Li/Na-ion batteries. However, irreversible loss of lattice oxygen aggravates a structural distortion to a spinel phase, which leads to severe voltage decay and capacity degeneration. Herein, via chemical ion exchange procedure, the sodium within the alkali metal layer of a P2-type oxide precursor has been substituted by Li while the transition metal layer can be well preserved, resulting in the formation of a Li-excess O2-type layered oxide cathode, Li0.66[Li0.12Ni0.15Mn0.73]O2. Through systematic in/ex-situ and surface/bulk characterization (hard X-ray absorption spectroscopy, operando Raman/XRD and differential electrochemical mass spectroscopy, etc.), the redox reversibility and structural stability has been comprehensively demonstrated. Moreover, being evolved from the same sodium-based precursor, a similar O2-type compound generated by electrochemical ion exchange procedure presents severely irreversible behavior on both structural and redox processes. These findings elucidated that the chemical ion exchange strategy can be regarded as an efficient way to design high-capacity cathode candidates possessing stable anionic/cationic redox activities and enhanced structural stability.

Routes to develop a [S]/([S]+[Se]) gradient in wide band-gap Cu2ZnGe(S,Se)4 thin-film solar cells

Wide band-gap kesterite-based solar cells are very attractive to be used for tandem devices as well as for semi-transparent photovoltaic cells. Here, Cu2ZnGe(S,Se)4 (CZGSSe) thin films have been grown by sulfurization of co-evaporated Cu2ZnGeSe4. The influence of a NaF precursor layer and of a Se capping film on CZGSSe absorbers and solar cells has been investigated. It has been found that the distribution of [S]/([S]+[Se]) through the CZGSSe absorber layer is strongly dependent on the Na content. Na promotes the diffusion of S towards the bulk of the absorber layer. Thicker NaF layers>6 nm lead to a higher S content in the bulk of the absorber layer, but to a decreased accumulation of sulphur at the surface, as detected by GIXRD, GD-OES, and Raman spectroscopy measurements. A relationship between Jsc, FF and Na-content supplied was found; higher Na content resulted in improved solar cell efficiencies. It has also been possible to modify the [S]/([S]+[Se])-gradient throughout the CZGSSe film by the absence of the Se capping layer, achieving devices with 2.7% performance and Eg = 2.0 eV. This work reveals two ways to control the [S]/([S]+[Se]) depth-profile to produce wide band gap CZGSSe absorber layers for efficient solar cells.