Effects of combined heat and light soaking on device performance of Cu(In,Ga)Se2 solar cells with ZnS(O,OH) buffer layer

The impacts of air annealing, light soaking (LS), and heat–light soaking (HLS) on cell performances were investigated for ZnS(O,OH)/Cu(In,Ga)Se₂ (CIGS) thin‐film solar cells. It was found that the HLS post‐treatment, a combination of LS and air annealing at 130 °C, is the most effective process for improving the cell performances of ZnS(O,OH)/CIGS devices. The best solar cell yielded a total area efficiency of 18.4% after the HLS post‐treatment. X‐ray photoelectron spectroscopy showed that the improved cell performance was attributable to the decreased S/(S + O) atomic ratio, not only in the surface region but also the interface region between the ZnS(O,OH) and CIGS layers, implying the shift to an adequate conduction‐band offset at the ZnS(O,OH)/CIGS interface. Copyright © 2013 John Wiley & Sons, Ltd.     

Interface Analysis of Cu(In,Ga)Se2 and ZnS Formed Using Sulfur Thermal Cracker

We analyzed the interface characteristics of Zn‐based thin‐film buffer layers formed by a sulfur thermal cracker on a Cu(In,Ga)Se₂ (CIGS) light‐absorber layer. The analyzed Zn‐based thin‐film buffer layers are processed by a proposed method comprising two processes — Zn‐sputtering and cracker‐sulfurization. The processed buffer layers are then suitable to be used in the fabrication of highly efficient CIGS solar cells. Among the various Zn‐based film thicknesses, an 8 nm–thick Zn‐based film shows the highest power conversion efficiency for a solar cell. The band alignment of the buffer/CIGS was investigated by measuring the band‐gap energies and valence band levels across the depth direction. The conduction band difference between the near surface and interface in the buffer layer enables an efficient electron transport across the junction. We found the origin of the energy band structure by observing the chemical states. The fabricated buffer/CIGS layers have a structurally and chemically distinct interface with little elemental inter‐diffusion.     

Interface engineering and characterization at the atomic‐scale of pure and mixed ion layer gas reaction buffer layers in chalcopyrite thin‐film solar cells

In this work, we investigate the p–n junction region for two different buffer/Cu(In,Ga)(Se,S)₂ (CIGSSe) samples having different conversion efficiencies (the cell with pure In₂S₃ buffer shows a lower efficiency than the nano‐ZnS/In₂S₃ buffered one). To explain the better efficiency of the sample with nano‐ZnS/In₂S₃ buffer layer, combined transmission electron microscopy, atom probe tomography, and X‐ray photoelectron spectroscopy studies were performed. In the pure In₂S₃ buffered sample, a CuIn₃Se₅ ordered‐defect compound is observed at the CIGSSe surface, whereas in the nano‐ZnS/In₂S₃ buffered sample no such compound is detected. The absence of an ordered‐defect compound in the latter sample is explained either by the presence of the ZnS nanodots, which may act as a barrier layer against Cu diffusion in CIGSSe hindering the formation of CuIn₃Se₅, or by the presence of Zn at the CIGSSe surface, which may disturb the formation of this ordered‐defect compound. In the nano‐ZnS/In₂S₃ sample, Zn was found in the first monolayers of the absorber layer, which may lead to a downward band bending at the surface. This configuration is very stable (Fermi level pinning at the conduction band, as observed for Cd in Cu(In,Ga)Se₂) and reduces the recombination rate at the interface. This effect may explain why the sample with ZnS nanodots possesses a higher efficiency. This work demonstrates the capability of correlative transmission electron microscopy, atom probe tomography, and X‐ray photoelectron spectroscopy studies in investigating buried interfaces. The study provides essential information for understanding and modeling the p–n junction at the nanoscale in CIGSSe solar cells. Copyright © 2014 John Wiley & Sons, Ltd.     

Improved fill factor and open circuit voltage by crystalline selenium at the Cu(In,Ga)Se2/buffer layer interface in thin film solar cells

A surface treatment by evaporated selenium on Cu(In,Ga)Se₂ (CIGS) is shown to improve open circuit voltage, V_oc, and in some cases fill factor, FF, in solar cells with CdS, (Zn,Mg)O or Zn(O,S) buffer layers. V_oc increases with increasing amount of crystalline Se, while FF improves only for small amounts. The improvements are counteracted by a decreasing short circuit current assigned to absorption in hexagonal Se. Improved efficiency is shown for device structures with (Zn,Mg)O and Zn(O,S) buffer layers by atomic layer deposition. Analysis by grazing incidence X‐ray diffraction and photoelectron spectroscopy show partial coverage of the CIGS surface by hexagonal selenium. The effects on device performance from replacing part of the CIGS/buffer interface area by a Se/buffer junction are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Study on ALD In2S3/Cu(In,Ga)Se2 interface formation

The formation of the interface between In₂S₃ grown by atomic layer deposition (ALD) and co‐evaporated Cu(In,Ga)Se₂ (CIGS) has been studied by X‐ray and UV photoelectron spectroscopy. The valence band offset at 160°C ALD substrate temperature was determined as −1·2±0·2 eV for CIGS deposited on soda‐lime glass substrates and −1·4±0·2 eV when a Na barrier substrate was used. Wavelength dependent complex refractive index of In₂S₃ grown directly on glass was determined from inversion of reflectance and transmittance spectra. From these data, an indirect optical bandgap of 2·08±0·05 eV was deduced, independent of film thickness, of substrate temperature and of Na content. CIGS solar cells with ALD In₂S₃ buffer layers were fabricated. Highest device efficiency of 12·1% was obtained at a substrate temperature of 120°C. Using the bandgap obtained for In₂S₃ on glass and a 1·15±0·05 eV bandgap determined for the bulk of the CIGS absorber, the conduction band offset at the buffer interface was estimated as −0·25±0·2 eV (−0·45±0·2 eV) for Na‐containing (Na‐free) CIGS. Copyright © 2005 John Wiley & Sons, Ltd.     

Minimizing metastabilities in Cu(In,Ga)Se2/(CBD)Zn(S,O,OH)/i‐ZnO‐based solar cells

Chemical bath deposited (CBD)Zn(S,O,OH) is among the alternatives to (CBD)CdS buffer layers in Cu(In,Ga)Se₂(CIGSe)‐based devices. Nevertheless, the performances reached by devices buffered with (CBD)Zn(S,O,OH) vary strongly from one sample to another and from one laboratory to another, indicating that parameters of minority impact with (CBD)CdS‐buffered devices have major influence when buffered with (CBD)Zn(S,O,OH). Moreover, the literature reports, but not systematically, the requirement of substituting the standard resistive intrinsic ZnO by (Zn,Mg)O and/or soaking the devices in ultraviolet‐containing light in order to reach optimal device operation. The present study investigates the impact of the three following parameters on the optoelectronic behavior of the Cu(In,Ga)Se₂/(CBD)Zn(S,O,OH)/i‐ZnO‐based solar cells: (i) CIGSe surface composition; (ii) (CBD)Zn(S,O,OH) layer thickness; and (iii) i‐ZnO layer resistivity. The first conclusion of this study is that all of these parameters are observed to influence the electrical metastabilities of the devices. The second conclusion is that the light soaking time needed to achieve optimal photovoltaic parameters is decreased by (i) using absorbers with Cu content close to stoichiometry, (ii) increasing the buffer layer thickness, and (iii) increasing the resistivity of i‐ZnO. By optimizing these trends, stable and highly efficient Zn(S,O,OH)‐buffered CIGSe solar cells have been fabricated. Copyright © 2014 John Wiley & Sons, Ltd.     

World‐record Cu(In,Ga)Se2‐based thin‐film sub‐module with 17.4% efficiency

We report a new certified world‐record efficiency for thin‐film Cu(In,Ga)Se₂‐based photovoltaic sub‐modules of 17.4% (aperture area). The record efficiency of the 16 cm², monolithically integrated, sub‐module has been independently confirmed by Fraunhofer ISE. The record device is the result of extensive co‐optimization of all processing steps. During the optimization process, strong focus has been put on the scalability of processes to cost‐effective mass production, as reflected, for example, in Cu(In,Ga)Se₂ deposition time and substrate temperature. Device manufacturing as well as results of electrical and material characterization is discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Device characteristics of a 10.1% hydrazine‐processed Cu2ZnSn(Se,S)4 solar cell

A power conversion efficiency record of 10.1% was achieved for kesterite absorbers, using a Cu₂ZnSn(Se,S)₄ thin‐film solar cell made by hydrazine‐based solution processing. Key device characteristics were compiled, including light/dark J–V, quantum efficiency, temperature dependence of V_oc and series resistance, photoluminescence, and capacitance spectroscopy, providing important insight into how the devices compare with high‐performance Cu(In,Ga)Se₂. The record kesterite device was shown to be primarily limited by interface recombination, minority carrier lifetime, and series resistance. The new level of device performance points to the significant promise of the kesterites as an emerging and commercially interesting thin‐film technology. Copyright © 2011 John Wiley & Sons, Ltd.     

SHORT COMMUNICATION: ACCELERATED PUBLICATION: Diode characteristics in state‐of‐the‐art ZnO/CdS/Cu(In1−xGax)Se2 solar cells

We report a new state of the art in thin‐film polycrystalline Cu(In,Ga)Se₂‐based solar cells with the attainment of energy conversion efficiencies of 19·5%. An analysis of the performance of Cu(In,Ga)Se₂ solar cells in terms of some absorber properties and other derived diode parameters is presented. The analysis reveals that the highest‐performance cells can be associated with absorber bandgap values of ∼1·14 eV, resulting in devices with the lowest values of diode saturation current density (∼3×10⁻⁸ mA/cm²) and diode quality factors in the range 1·30 < A < 1·35. The data presented also support arguments of a reduced space charge region recombination as the reason for the improvement in the performance of such devices. In addition, a discussion is presented regarding the dependence of performance on energy bandgap, with an emphasis on wide‐bandgap Cu(In,Ga)Se₂ materials and views toward improving efficiency to > 1;20% in thin‐film polycrystalline Cu(In,Ga)Se₂ solar cells. Published in 2005 John Wiley & Sons, Ltd.     

Impact of compositional grading and overall Cu deficiency on the near‐infrared response in Cu(In,Ga)Se2 solar cells

Highly efficient thin film solar cells based on co‐evaporated Cu(In,Ga)Se₂ (CIGS) absorbers are typically grown with a [Ga]/([Ga] + [In]) (GGI) gradient across the thickness and a Cu‐poor composition. Upon increasing the Cu content towards the CIGS stoichiometry, lower defect density is expected, which should lead to increased absorption in the near‐infrared (NIR), diffusion length and carrier collection. Further, optimization of the GGI grading is expected to increase the NIR response. In this contribution [Cu]/([In] + [Ga]) (CGI) values are increased by shortening the deposition stage after the first stoichiometric point. In order to obtain comparable Ga contents at the interface for proper band alignment, the front GGI gradings were actively modified. With a relative CGI increase of 7%, we observe an increased photocurrent, originating from an improved NIR external quantum efficiency response. By characterizing the modified absorber properties by reflection‐transmission spectroscopy, we attribute the observed behavior to changes in the optical properties rather than to improved carrier collection. Cu‐dependent modifications of the NIR‐absorption coefficients are likely to be responsible for the variations in the optical properties, which is supported by device simulations. Adequate re‐adjustments of the co‐evaporation process and of the alkali‐fluorides post‐deposition treatments allow maintaining V_oc and FF values, yielding an overall increase of efficiency as compared to a reference baseline. © 2016 The Authors. Progress in Photovoltaics : Research and Applications published by John Wiley & Sons Ltd.     

Record 1.0 V open‐circuit voltage in wide band gap chalcopyrite solar cells

Tandem solar cell structures require a high‐performance wide band gap absorber as top cell. A possible candidate is CuGaSe₂, with a fundamental band gap of 1.7 eV. However, a significant open‐circuit voltage deficit is often reported for wide band gap chalcopyrite solar cells like CuGaSe₂. In this paper, we show that the open‐circuit voltage can be drastically improved in wide band gap p‐Cu(In,Ga)Se₂ and p‐CuGaSe₂ devices by improving the conduction band alignment to the n‐type buffer layer. This is accomplished by using Zn_1−x Sn_x O_y , grown by atomic layer deposition, as a buffer layer. In this case, the conduction band level can be adapted to an almost perfect fit to the wide band gap Cu(In,Ga)Se₂ and CuGaSe₂ materials. With an improved buffer band alignment for CuGaSe₂ absorbers, evaporated in a 3‐stage type process, we show devices exhibiting open‐circuit voltages up to 1017 mV, and efficiencies up to 11.9%. This is to the best of our knowledge the highest reported open‐circuit voltage and efficiency for a CuGaSe₂ device. Temperature‐dependent current‐voltage measurements show that the high open‐circuit voltage is explained by reduced interface recombination, which makes it possible to separate the influence of absorber quality from interface recombination in future studies.     

Development of gallium gradients in three‐stage Cu(In,Ga)Se2 co‐evaporation processes

We use secondary‐ion mass spectrometry, X‐ray diffraction and scanning electron microscopy to investigate the development over time of compositional gradients in Cu(In,Ga)Se₂ thin films grown in three‐stage co‐evaporation processes and suggest a comprehensive model for the formation of the well‐known ‘notch’ structure. The model takes into account the need for compensating Cu diffusion by movement of group‐III ions in order to remain on the quasi‐binary tie line and indicates that the mobilities of In and Ga ions differ. Cu diffuses towards the back in the second stage and towards the front in the third, and this is the driving force for the movement of In and Ga. The [Ga]/[In + Ga] ratio then increases in the direction of the respective Cu movement because In has a higher mobility at process conditions than has Ga. Interdiffusion of In and Ga can be considerable in the (In,Ga)₂Se₃ film of the first stage, but seems largely to cease in Cu(In,Ga)Se₂ and shows no signs of being boosted by the presence of a Cu₂Se layer. Copyright © 2011 John Wiley & Sons, Ltd.     

13·7%-Efficient Zn(Se,OH)x/Cu(In,Ga)(SSe)2 thin-film solar cell

Cu(In,Ga)Se₂ (CIGS) and related semiconducting compounds have demonstrated their high potential for high-efficiency thin-film solar cells. The highest efficiency for CIGS-based thin-film solar cells has been achieved with CdS buffer layers prepared by a solution growth method known as chemical bath deposition (CBD). With the aim of developing Cd-free chalcopyrite-based thin-film solar cells, Zn(Se,OH)_x buffer layers were deposited by CBD on polycrystalline Cu(In,Ga)(S,Se)₂ (CIGSS). A total-area conversion efficiency of 13·7% was certified by the Frauenhofer Institute for Solar Energy Systems. The CIGSS absorber was fabricated by Siemens Solar Industries (California). For device optimization, the thickness and good surface coverage were controlled by XPS–UPS photoemission spectroscopy. A Zn(Se,OH)_x thickness below 7 nm has been found to be optimum for achieving a homogeneous and compact buffer film on CIGSS, with open-circuit photovoltage V_oc=535 mV, fill factor FF=70·76% and a high short-circuit photocurrent density J_sc=36·1 mA cm⁻². Copyright © 1998 John Wiley & Sons, Ltd.     

A comparative study of Cd‐ and Zn‐compound buffer layers on Cu(In1−x,Gax)(Sy,Se1−y)2 thin film solar cells

This paper reports a comparative study of Cu(In,Ga)(S,Se)₂ (CIGSSe) thin‐film solar cells with CBD‐CdS, CBD‐ZnS(O,OH) and ALD‐Zn(O,S) buffer layers. Each buffer layer was deposited on CIGSSe absorber layers which were prepared by sulfurization after selenization (SAS) process by Solar Frontier K. K. Cell efficiencies of CBD‐CdS/CIGSSe, CBD‐ZnS(O,OH)/CIGSSe and ALD‐Zn(O,S)/CIGSSe solar cells exceeded 18%, for a cell area of 0.5 cm². The solar cells underwent a heat‐light soaking (HLS) post‐treatment at 170 °C under one‐sun illumination in the air; among the three condtions, the ALD‐Zn(O,S)/CIGSSe solar cells showed the highest cell efficiency of 19.78% with the highest open‐circuit voltage of 0.718 V. Admittance spectroscopy measurements showed a shift of the N₁ defect's energy position toward shallower energy positions for ALD‐Zn(O,S)/CIGSSe solar cells after HLS post‐treatment, which is in good agreement with their higher open‐circuit voltage and smaller interface recombination than that of CBD‐ZnS(O,OH)/CIGSSe solar cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamic radiative properties of the Cu(In,Ga)Se2 layer during the co‐evaporation process

A study of the wavelength‐integrated emissivity has been performed on the optical stack Cu_xSe/Cu(In,Ga)Se₂/Mo. The wavelength interval used in the study was 2–20 µm, which covers 95% of the radiated heat from a black body heated to 500°C. Substrate temperatures around 500°C are commonly used in production of Cu(In,Ga)Se₂ thin films for solar cells. The integrated emissivity was obtained from directional reflectivity measurements of experimental samples with different thicknesses of the Cu_xSe layers. It was subsequently compared to the emissivity from numerical simulations based on newly obtained values of the refractive index values for Cu(In,Ga)Se₂ and Cu_xSe at these wavelengths. Good agreement was found between the measured and simulated values. At a Cu(In,Ga)Se₂ thickness of 1.8 µm and a Mo thickness of 400 nm, a maximum in the integrated emissivity was found for a Cu_xSe thickness of 30 nm. The results are valuable input into understanding the dynamics of the change in emissivity between Cu‐rich Cu(In,Ga)Se₂ with segregated Cu_xSe and Cu‐poor single phase Cu(In,Ga)Se₂ at temperatures around 500°C. In co‐evaporation of Cu(In,Ga)Se₂, this emissivity change is often monitored and used as a process control (end‐point detection). Copyright © 2010 John Wiley & Sons, Ltd.     

Failure analysis of Cu(In,Ga)Se2 photovoltaic modules: degradation mechanism of Cu(In,Ga)Se2 solar cells under harsh environmental conditions

High‐temperature‐induced and humidity‐induced degradation behaviors were investigated through the failure analysis of encapsulated Cu(In,Ga)Se₂ (CIGS) modules and non‐encapsulated CIGS cells. After being exposed to high temperature (85 °C) for 1000 h, the efficiency loss of CIGS modules and the resistivities of the aluminum‐doped zinc oxide (AZO) layer, CIGS layer, and Mo layer were slightly increased. After damp heat (DH) testing (85 °C/85% RH), the efficiency of some modules decreased significantly accompanied by discoloration, and in these areas, the resistivity of the AZO layers increased markedly. The causes of degradation of CIGS cells after high temperature and DH tests were suggested through X‐ray photoelectron spectroscopy analysis. The high‐temperature‐induced degradation behaviors were revealed to be increases in series resistance of the CIGS cells, due to the adsorption of oxygen on the AZO, CIGS, and Mo layers. The degradation behavior after DH (85 °C/85% RH) exposure was caused by the adsorption of oxygen, as well as the generation of Zn(OH)₂ due to water molecules. In particular, the humidity‐induced degradation behavior in discolored CIGS modules was ascribed to the generation of Zn(OH)₂ and carboxylic acids in the AZO layer, due to a chemical reaction between the AZO, ethylene‐vinyl acetate copolymer, and water. Copyright © 2014 John Wiley & Sons, Ltd.     

Highly‐efficient Cd‐free CuInS2 thin‐film solar cells and mini‐modules with Zn(S,O) buffer layers prepared by an alternative chemical bath process

Recent progress in fabricating Cd‐ and Se‐free wide‐gap chalcopyrite thin‐film solar devices with Zn(S,O) buffer layers prepared by an alternative chemical bath process (CBD) using thiourea as complexing agent is discussed. Zn(S,O) has a larger band gap (E_g = 3·6–3·8 eV) than the conventional buffer material CdS (E_g = 2·4 eV) currently used in chalcopyrite‐based thin films solar cells. Thus, Zn(S,O) is a potential alternative buffer material, which already results in Cd‐free solar cell devices with increased spectral response in the blue wavelength region if low‐gap chalcopyrites are used. Suitable conditions for reproducible deposition of good‐quality Zn(S,O) thin films on wide‐gap CuInS₂ (‘CIS’) absorbers have been identified for an alternative, low‐temperature chemical route. The thickness of the different Zn(S,O) buffers and the coverage of the CIS absorber by those layers as well as their surface composition were controlled by scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray excited Auger electron spectroscopy. The minimum thickness required for a complete coverage of the rough CIS absorber by a Zn(S,O) layer deposited by this CBD process was estimated to ∼15 nm. The high transparency of this Zn(S,O) buffer layer in the short‐wavelength region leads to an increase of ∼1 mA/cm² in the short‐circuit current density of corresponding CIS‐based solar cells. Active area efficiencies exceeding 11·0% (total area: 10·4%) have been achieved for the first time, with an open circuit voltage of 700·4 mV, a fill factor of 65·8% and a short‐circuit current density of 24·5 mA/cm² (total area: 22·5 mA/cm²). These results are comparable to the performance of CdS buffered reference cells. First integrated series interconnected mini‐modules on 5 × 5 cm² substrates have been prepared and already reach an efficiency (active area: 17·2 cm²) of above 8%. Copyright © 2006 John Wiley & Sons, Ltd.     

Investigation of Cu(In,Ga)Se2 thin‐film formation during the multi‐stage co‐evaporation process

In order to transfer the potential for the high efficiencies seen for Cu(In,Ga)Se₂ (CIGSe) thin films from co‐evaporation processes to cheaper large‐scale deposition techniques, a more intricate understanding of the CIGSe growth process for high‐quality material is required. Hence, the growth mechanism for chalcopyrite‐type thin films when varying the Cu content during a multi‐stage deposition process is studied. Break‐off experiments help to understand the intermediate growth stages of the thin‐film formation. The film structure and morphology are studied by X‐ray diffraction and scanning electron microscopy. The different phases at the film surface are identified by Raman spectroscopy. Depth‐resolved compositional analysis is carried out via glow discharge optical emission spectrometry. The experimental results imply an affinity of Na for material phases with a Cu‐poor composition, affirming a possible interaction of sodium with Cu vacancies mainly via In(Ga)_Cu antisite defects. An efficiency of 12.7% for vacancy compound‐based devices is obtained. Copyright © 2011 John Wiley & Sons, Ltd.     

Growth mechanisms of co‐evaporated kesterite: a comparison of Cu‐rich and Zn‐rich composition paths

Earth abundant kesterite solar cells have achieved 7–10% cell efficiency mostly by processes that separate the film deposition and the annealing into two sequential steps. In contrast, co‐evaporation onto a high‐temperature substrate, demonstrating previous success in chalcopyrite (Cu(In,Ga)Se₂) solar cells, allows real‐time composition control. Chalcopyrite research widely supports the model that Cu‐rich growth conditions assist grain growth, and subsequently, the endpoint composition can be adjusted back to Cu‐poor via monitoring the surface emissivity of the film. On the basis of the same intentions, the recent development of co‐evaporated kesterite (Cu₂ZnSnSe₄) adapts the concept and achieves 9.2% efficiency. To understand the effect of growth strategies, this study examines the phase evolution, grain morphology, and device performance in Cu‐rich growth and other strategies (Zn‐rich and close‐to‐stoichiometric). By characterizing films obtained from interrupted depositions and also interpreting the variation in surface emission during growths, this study found a subtle hindrance in the reaction of Cu_xSe_y and ZnSe possibly caused by the volatile nature of SnSe_x. The hindrance explains why, distinctive from chalcopyrite, little difference in grain size is observed between kesterite films made by Cu‐rich versus Zn‐rich growth at these deposition rates. At last, a Zn‐rich growth 9.1% device, certified by the National Renewable Energy Laboratory, is presented, which equals the performance of the previously‐reported Cu‐rich growth device. At the present stage, we believe the Cu‐rich and Zn‐rich growth share equal promise for the optimization of kesterite solar cells. Copyright © 2013 John Wiley & Sons, Ltd.     

The Zn(S,O,OH)/ZnMgO buffer in thin film Cu(In,Ga)(S,Se)2‐based solar cells part I: Fast chemical bath deposition of Zn(S,O,OH) buffer layers for industrial application on Co‐evaporated Cu(In,Ga)Se2 and electrodeposited CuIn(S,Se)2 solar cells

This paper is focused on the basic study and optimization of short time (<10 min) Chemical Bath Deposition (CBD) of Zn(S,O,OH) buffer layers in co‐evaporated Cu(In,Ga)Se₂ (CIGSe) and electrodeposited CuIn(S,Se)₂ ((ED)‐CIS) solar cells for industrial applications. First, the influence of the deposition temperature is studied from theoretical solution chemistry considerations by constructing solubility diagrams of ZnS, ZnO, and Zn(OH)₂ as a function of temperature. In order to reduce the deposition time under 10 min, experimental growth deposition studies are then carried out by the in situ quartz crystal microgravimetry (QCM) technique. An optimized process is performed and compared to the classical Zn(S,O,OH) deposition. The morphology and composition of Zn(S,O,OH) films are determined using SEM and XPS techniques. The optimized process is tested on electrodeposited‐CIS and co‐evaporated‐CIGSe absorbers and cells are completed with (Zn,Mg)O/ZnO:Al windows layers. Efficiencies similar or even better than CBD CdS/i‐ZnO reference buffer layers are obtained (15·7% for CIGSe and 8·1% for (ED)‐CIS). Copyright © 2009 John Wiley & Sons, Ltd.