A study of the CdTe treatment with a Freon gas such as CHF2Cl

Mazzamuto, S.; Vaillant, L.; Bosio, A.; Romeo, N.; Armani, N.; Salviati, G.

doi:10.1016/j.tsf.2007.12.124

Cited by 42 publications

(41 citation statements)

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“…Some researchers deposited solid CdCl 2 layers on top of CdTe surfaces using many different techniques such as vacuum evaporation [43], and in some cases CdCl 2 layer thickness was comparable to that of CdTe layer [44]. Literature also shows the use of Freon gas (CHF 2 Cl) to introduce Cl and F during post growth heat treatment of CdTe layer [45]. Other methods such as the use of HCl vapour to introduce Cl [46] during growth have also been reported.…”

Section: Post-growth Heat Treatmentmentioning

confidence: 99%

Unravelling complex nature of CdS/CdTe based thin film solar cells

Dharmadasa

Ojo

2017

J Mater Sci: Mater Electron

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and high-temperature growth techniques. The wide bandgap (E g = 2.42 eV) window material, CdS was mainly grown by chemical bath deposition (CBD) and narrow bandgap (E g = 1.45 eV) absorber material, CdTe was grown by over 14 different methods [1]. High efficiencies were achieved by the combination of CdS with CdTe layers grown by high temperature growth methods such as closed space sublimation (CSS) or close spaced vapour transport (CSVT) for a long period. Depending on the growth technique, material growth mechanisms, micro-structure and impurity inclusions are going to vary. Although there are a large number of publications reporting material characterisation, deep understanding is required on material issues such as defects and doping concentrations.The next area needing deeper understanding is the postgrowth chemical and heat treatment. The devices fabricated using as-made CdTe materials show poor device performance in the range ~(0-6)% depending on the growth technique used. However, from 1976 [2], the researchers were aware of the drastic improvement of the device performance after heat treatment around 450 °C in air, in the presence of CdCl 2 . This was known as "CdCl 2 treatment" and device efficiencies improved to mid-teens achieving good solar cell performance. Although there were tremendous efforts to explore the complexity of changes during this treatment, full understanding has not yet been achieved.The third main area of complexity comes from the CdTe/electrical back contact formation. It is essential to clean the CdTe surface after CdCl 2 treatment, and researchers were using different chemicals to clean the surface prior to metallisation. Various electrical contacts have been used to complete the devices and varying results have been reported in the literature [3]. Initial high efficiency, reproducibility and yield, stability and lifetime are main features of fully fabricated devices to establish. Some of these Abstract Thin film solar cells based on CdS/CdTe hetero-structure has shown a drastic improvement changing from 16.5 to 22.1% efficiency during a short period of time from ~2013 to ~2016. This has happened in the industrial environment and the open research in this field has stagnated over a period of two decades prior to ~2013. Most of the issues of this hetero-structure were not clear to the photovoltaic (PV) community and research efforts should be directed to unravel its complex nature. Issues related to materials, post-growth treatment, chemical etching prior to metallisation and associated device physics are the main areas needing deeper understanding in order to further develop this device. After a comprehensive research programme in both academia and in industry on these materials, surfaces and interfaces and fully fabricated devices over a period of over three decades by the main author, the current knowledge as understood today, on all above mentioned complex issues are presented in this paper. Full understanding of this structure will enable PV developers to further improve the ...

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Section: Post-growth Heat Treatmentmentioning

confidence: 99%

Unravelling complex nature of CdS/CdTe based thin film solar cells

Dharmadasa

Ojo

2017

J Mater Sci: Mater Electron

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“…Most of the high-efficiency CdTe-based solar cells reported in the literature have employed CdTe materials with randomly oriented crystallites depicted by the type of XRD pattern shown in figure 4(d) [14,25,26]. The CdTe samples treated with CdCl 2 +CdF 2 should therefore produce CdTe solar cells with improved efficiency compared to those treated with only CdCl 2 .…”

Section: Structural Characterisation -X-ray Diffractionmentioning

confidence: 99%

“…These properties have been studied to certain extent to date [9][10][11][12]. For photovoltaic application in particular, these studies have mainly concentrated on CdCl 2 -treated CdTe since CdCl 2 treatment is a crucial step in the fabrication of high efficiency CdTe-based solar cells [13][14][15]. The improvement in solar cell efficiency in this case is attributed to the diffusion of Cl into CdTe.…”

Section: Introductionmentioning

confidence: 99%

“…The improvement in solar cell efficiency in this case is attributed to the diffusion of Cl into CdTe. As a modification of the CdCl 2 treatment, Mazzamuto et al [14] and Rio-Flores et al [16] have tried to incorporate Cl into CdTe during post-deposition heat treatment by using a mixture of argon and a Freon gas (CHF 2 Cl) which contains both Cl and F atoms to achieve improved solar cell efficiency [14]. Recently, authors of the present work have incorporated Cl and F atoms into CdTe through the use of a mixture of CdCl 2 and CdF 2 in the post-deposition heat treatment of CdTe to obtain improved solar cell efficiency compared to the use of only CdCl 2 treatment [17].…”

Section: Introductionmentioning

confidence: 99%

“…This improvement has also been attributed to the higher diffusion property of F compared to Cl. These recent results by the authors' group [17] as well as those of Mazzamuto et al [14] and Rio-Flores et al [16] have necessitated the detailed study of the effects of annealing of CdTe with CdCl 2 treatment, CdCl 2 +CdF 2 treatment and without chemical treatment, on the structural and optical properties of electrodeposited CdTe thin films of different thicknesses, in order to further understand how these treatments impact the properties of CdTe for solar cell efficiency improvement. It is pertinent also to observe that although some optical properties of CdTe have been studied at different times [12,18], comprehensive study of the effect of different annealing conditions (with prior CdCl 2 and CdCl 2 +CdF 2 treatments) on the entire optical parameters (transmittance, absorbance, reflectance, absorption coefficient, extinction coefficient, refractive index and dielectric constant) of CdTe has not been reported in a single publication.…”

Section: Introductionmentioning

confidence: 99%

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