CBD ZnS

Figure 7.1. The current-voltage plot for an 18.5%-efficient CBD ZnS(O.OH)/CIGS-based photovoltaic device. Device temperature 25.0 + 1°C Device area = 0.402cm2 Irradiance 1000.0W/m2 V

Figure 7.3. FTIR spectra of NREL CBD ZnS(0,0H) annealed NREL CBD ZnS(0,0H) standard ZnS(0,0H) Alfa-ZnS, Alfa-ZnS04, and Alfa-ZnO (all Alfa chemicals analyzed were as-received from the chemical company). [Reproduced with permission from Ref. 38(b). Copyright 2005 Elsevier Limited.]...

Perhaps the best compromise to eliminate the high concentration of hydroxide and oxide impurities could be to use a CBD Cd xZnxS (denoted as CdZnS) buffer layer instead of a CBD ZnS(0,0H) buffer layer, if Cd does not pose a significant environmental issue. The use of CdZnS has multiple advantages. In high Cd-containing CdZnS, the oxide and hydroxide impurities are mini-... 

Gangopadhyay et al.48 used a CBD ZnS antireflection coating on large-area commercial monocrystalline silicon solar cells, resulting in a 13.8% efficiency. Ennaoui et al.49 deposited CBD Zn(Se,OH)x films on Cu(In,Ga)(S,Se)2. They reported an active-area efficiency of up to 15.7% and a total-area efficiency of up to 13.26% for such devices. 

Aguilar et al.54 prepared CBD ZnS and CuS to develop architectural glazing capable of withstanding hot tropical climates and windstorms. Lipowsky... 

Nakada, T. Mizutani, M. Hagiwara, Y. Kunioka, A. 2001. High-efficiency Cu(In,Ga)Se2 thin-film solar cells with a CBD-ZnS buffer layer. Solar Energy Mater. Solar Cells 67 255-260. 

Gangopadhyay, U. Kim, K. Mangalaraj, D. Junsin, Y. 2004. Low cost CBD ZnS antireflection coating on large area commercial mono-crystalline silicon solar cells. Appl. Surf. Sci. 230 364-370. 

The first CBD ZnS-based buffer fabrication was done with an efficiency level of 9-10% [262]. In the CBD of ZnS buffer, thiourea is generally used as the sulfur source and ammonia as complexing agent [259]. The quality of the ZnS films, and their solar performance, is controlled by the concentration of ammonia. In particular, depending on this concentration, co-deposition of ZnS, ZnO, and Zn(OH)2 may occur resulting in many different possible compositions and phases (ZnS,... 

It should be stressed that the key point in the recent success of ZnS application in thin film solar cells is the use of chemical rather than electrochemical deposition (CBD), which is successfully applied also for obtaining Cdi- Zn S films. Note though that smdies on the chemical growth of ZnS are limited compared to CdS, and the level of understanding of the deposition mechanism is inferior. 

CBD is a process which can take place over a period of time that can range from a few minutes to over several hours. The thickness of the films is typically in the tens of nm to the micron range. Kinetic studies are classically based on ex situ film thickness determinations, using a mechanical profilometer [11], optical absorbance [42], or film composition [35]. Such a strategy for studying deposition kinetics was largely employed for a number of binary and ternary chalcogenides ([11] and references therein and more recent references about CdS [25, 31, 35, 42], ZnS [69], CdSe [77], ZnSe [92, 93], CuSe [92], 86283 [62]). 

As indicated above for cadmium sulfides and selenides, CBD is a well-known deposition process for some other chalcogenides such as sulfides and selenides of Zn, In, Co, Hg, Pb, Sb2S3 and Sb2Bi2 S3 [231]. The deposition of metal cholcoge-nide films is based of following properties of thiosulfate/selenosulfate [232]. 

ZnO, and Zn(OH)2) for the CBD process [261]. Optimal film compositions must be identified before large-scale preparation of these films for solar cell applications because CBD of ZnS is more complex and difficult than that of CdS [262]. Although significant efforts have been undertaken to make CIGS-based cells free ofCd, until now, such cells usually have lower efficiency and less reproducible behavior than their Cd-containing counterparts. The continued investigation of the deposition conditions leading to superior film properties for the CBD of ZnS in basic aqueous ammonia solutions would be worthwhile. 

A simple CBD method was employed to deposit ZnS thin films onto glass substrates using thiourea as sulfide ion source and zinc acetate as zinc ion source in an alkaline bath. For the preparation of ZnS thin films, 0.2 M zinc acetate solution was mixed with an equal volume of 0.2 M thiourea, and ammonia solution was added slowly to form the complex the pH then was adjusted between 9 and 10 at 303 K [232]. 

ZnS thin films of different thicknesses were prepared by CBD using thiourea and zinc acetate as S " and Zn sources, respectively. Thermo-EMF measurement indicated that films prepared by this method are of n-type. ZnS thin films were prepared by decomposition of thiourea in an alkaline solution containing a zinc salt The reaction mechanism for deposition of ZnS films has been reported. In aqueous solution, zinc acetate dissociates to give Zn " ions. Hydrolysis of ammonia... 

ZnSe thin films were also deposited on glass substrates by the chemical hath deposition (CBD) method using method using zinc sulfate, sodiumselenosulfate, hydrazine hydrate, ammonia as precursors. The slow release of zinc ions (Zn ) and selenide ions (Se ) in the reaction solution facilitated the condensation of the ions on the substrate. The films were composed of spherical particles with a zinc blende phase. The particle size was influenced by the hydrazine hydrate concentration or zinc sulfate concentration. The electrochemical atomic layer deposition (EC-ALD) method was used to deposit ZnSe nanometer films on a multicarbon nanotubes/polyvinyl alcohol (CNTs/PVA) membrane. The morphology of the films varied with the ratio of the zinc to selenium. 

The chemical bath deposition (CBD) process uses a controlled chemical reaction to achieve the deposition of a thin film by precipitation. CBD has been used to prepare ZnS films (by route C). In a typical experiment, substrates are immersed in an alkaline solution containing the chalcogenide source, the metal ion and added base. A chelating agent is also added, in order to control the hydrolysis of the metal ioa The process rehes on the slow release of ions into an alkaline solution in which the free metal ion is buffered at a low concentration. 

Controlled oxidation of Zn in solution In this method, similar to CBD but also electrochemical in nature, a Zn substrate is immersed in an... 

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