Tandem solar cells deposited using hot-wire chemical vapor deposition

Veen, M.K. van; Werf, C.H.M. van der; Schropp, R.E.I.

doi:10.1016/j.jnoncrysol.2004.03.071

Cited by 34 publications

(32 citation statements)

References 5 publications

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“…A good measure of the filament condition is the filament resistance. It has been reported that the resistance of the filament (tantalum in this case) increases after each deposition, for every filament used [6,14]. This is attributed mainly to silicidation of the filament during the catalytic reactions.…”

Section: Discussionmentioning

confidence: 65%

“…Raman spectroscopy at a laser wavelength of 514.5 nm was employed to estimate the crystalline ratio of absorber layers as well as of complete solar cells. A structural transition between lc-Si:H and a-Si:H has been observed at a gas flow ratio of R H = H 2 / (SiH 4 + H 2 ) = 0.95 [6]. Silicon n-i-p stacks deposited on accompanying Corning 1737 glass substrates were investigated with cross-sectional transmission electron microscopy (XTEM).…”

Section: Methodsmentioning

confidence: 99%

“…It has been shown by many groups that the best solar cells contain nc-Si:H i-layers that are made in the regime near the transition between amorphous and microcrystalline silicon (lc-Si:H), and at a relatively low substrate temperature around 200°C where the opto-elec- tronic properties are optimal. From the device performance point of view, a shift of the deposition parameters to either side of the transition regime will eventually lead to a decrease in carrier generation (and thus a reduced short circuit current density J sc ) if the shift is to the a-Si:H side, or a deterioration in effective carrier collection (resulting in low open circuit voltage V oc and fill factor FF) if the shift is too far into the lc-Si:H side [6]. It is therefore important to carefully control the deposition parameters in order to keep the material structure optimal.…”

Section: Introductionmentioning

confidence: 99%

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Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

Franken

Stolk

et al. 2008

Journal of Non-Crystalline Solids

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Hydrogen profiling, i.e., decreasing the H 2 dilution during deposition, is a well-known technique to maintain a proper crystalline ratio of the nanocrystalline (nc-Si:H) absorber layers of plasma-enhanced chemical vapor-deposited (PECVD) thin film solar cells. With this technique a large increase in the energy conversion efficiency is obtained. Compared to PECVD, the unique characteristics of hot-wire CVD (HWCVD), such as the catalytic reactions, the absence of ion bombardment, the substrate heating by the filaments and filament aging effects, necessitate a different strategy for material and device optimization. We report in this paper the results of using a reverse H 2 profiling technique, i.e., increasing the H 2 dilution of silane instead of decreasing it, to improve the quality of HWCVD intrinsic nc-Si:H and the performance of this material in single junction n-i-p cells. Thus far, the efficiency of nc-Si:H n-i-p cells made on a stainless steel substrate with an Ag/ZnO textured back reflector has been improved to 8.5%, and the efficiency of triple junction solar cells with a structure of proto-Si:H(HWCVD) top cell/proto-SiGe:H (PECVD) middle cell/nc-Si:H (HWCVD, with reverse H 2 profiling) bottom cell has reached 10.9%. These efficiency values show the viability of n-i-p cells comprising HWCVD nanocrystalline i-layers.

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Section: Discussionmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

Franken

Stolk

et al. 2008

Journal of Non-Crystalline Solids

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“…The silicon layers were deposited in a multi-chamber ultra-high vacuum system called PASTA [11]. Doped layers (boron and phosphorus doped nc-Si:H) and intrinsic proto-SiGe:H [12] were prepared using 13.56 MHz PECVD [13], whereas HWCVD was applied to fabricate intrinsic proto-Si:H [4] and ncSi:H [5,9,10,14]. Two straight Ta filaments were used for the hot-wire deposition, through which a current of 10.5 A was passed, yielding a wire temperature of approximately 1850°C in vacuum, as measured by a pyrometer.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, it is considered to be a good alternative to conventional PECVD. At Utrecht University, we have been concentrating on developing thin film silicon based multijunction solar cells employing active layers made with HWCVD [5,9,10]. In this contribution, we summarize the major scientific challenges and achievements that we have experienced during the development of such devices.…”

Section: Introductionmentioning

confidence: 99%

On the development of single and multijunction solar cells with hot-wire CVD deposited active layers

Franken

Stolk

et al. 2008

Journal of Non-Crystalline Solids

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We present an overview of the scientific challenges and achievements during the development of thin film silicon based single and multijunction solar cells with hot-wire chemical vapor deposition (HWCVD) of the active silicon layers. The highlights discussed include the development of Ag/ZnO coatings with a proper roughness and morphology for optimal light trapping in single and multijunction thin film silicon solar cells, studies of the structural defects created by a rough substrate surface and their influence on the performance of nc-Si:H n-i-p single junction solar cells, and studies of the phase change during the growth of nc-Si:H by HWCVD and the use of a 'reverse' H 2 profiling technique to achieve nc-Si:H single junction n-i-p cells with high performance. Thus far, the best AM1.5 efficiency reached for n-i-p cells on stainless-steel with HWCVD i-layers is 8.6% for single junction nc-Si:H solar cells and 10.9% for triple junction solar cells. The opportunities for further improvement of cell efficiency are also discussed. We conclude that the uniqueness of HWCVD and of the i-layers deposited with this technique require some adjustments in the strategy for optimization of single or multijunction solar cells, such as using a reverse H 2 profiling technique for the deposition of nc-Si:H i-layers. However, the output performance of solar cells with HWCVD deposited i-layers is close to those with i-layers deposited by other techniques. The difference between the best nc-Si:H ni-p cells obtained so far in our lab and the reported best n-i-p cells with PECVD i-layers can be mainly attributed to the differences in the rough substrates and to the use of rather thin i-layers.

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Thin film nanocrystalline silicon and nanostructured interfaces for multibandgap triple junction solar cells

Schropp

Rath

et al. 2008

Surface & Interface Analysis

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We present the main research aspects encountered during the development of thin film silicon-based single and multijunction solar cells using hot-wire chemical vapor deposition (HWCVD) of the active silicon layers. First of all, a significant current enhancement is obtained by using textured Ag/ZnO back contacts instead of plain stainless steel. The textured interface acts as a diffuse scattering mirror, due to which the optical path in the cell is lengthened. We studied the root-mean-square (RMS) roughness by 2D atomic force microscopy (AFM) and found that the morphology of the surfaces needs to be controlled to avoid cavities and shunting paths. A further drawback of such rough metallic surfaces is the parasitic absorption due to surface particle plasmons. Nevertheless, optimized back reflectors lead to an enhancement of the photocurrent of as much as 50%. The second large step forward is the use of multijunction (tandem) cells, in which at least one of the cells contains nanocrystalline silicon. This material behaves optically like 1.1 eV material and, used in the bottom cell, it forms a perfect combination with the 1.7 eV amorphous material in the top cell. Using silicon germanium (1.5 eV) in the middle cell, our triple junction cells have reached nearly 11% efficiency and they are stable within 3% relative. The difference between the best single junction and triple junction n-i-p cells obtained so far in our lab and the reported best cells with plasma-enhanced chemical vapor deposition (PECVD) i-layers can be mainly attributed to the differences in the rough substrates and to the use of rather thin i-layers.

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Tandem solar cells deposited using hot-wire chemical vapor deposition

Cited by 34 publications

References 5 publications

Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

On the development of single and multijunction solar cells with hot-wire CVD deposited active layers

Thin film nanocrystalline silicon and nanostructured interfaces for multibandgap triple junction solar cells

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