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Journal ArticleDOI

Effects of Carbon Grading at the p/i Interface on the Open Circuit Voltage of p-i-n and n-i-p Amophous Silicon Solar Cells

01 Jan 1987-MRS Proceedings (Cambridge University Press)-Vol. 95, Iss: 1, pp 545-548
TL;DR: Carbon grading in the buffer layer at the p/i interface increases the open circuit voltage of both p-n and n-i-p amorphous silicon solar cells.
Abstract: Carbon grading in the buffer layer at the p/i interface increases the open circuit voltage of both p-i-n and n-i-p amorphous silicon solar cells. We propose that carbon grading enlarges the electric field and reduces the electron tunneling at the p/i interface.
Citations
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Proceedings ArticleDOI
01 Jan 1988
TL;DR: In this paper, an extensive study of V/sub oc/ in a-Si:H p-i-n solar cells deposited by photo-CVD (chemical vapor deposition) and plasma CVD was presented.
Abstract: Results are presented of an extensive study of V/sub oc/ in a-Si:H p-i-n solar cells deposited by photo-CVD (chemical vapor deposition) and plasma-CVD. The diode parameters under illumination have been analyzed for varying p-layer and carbon graded layer thicknesses and impurity levels. It is found that the diode factor is 1.5 and that the built-in voltage is 1.05 V for most cells, indicating that the diode mechanism does not evolve from diffusion to space-charge recombination. Instead, it is concluded that in typical devices V/sub oc/ is dominated by recombination at the p/i junction. The author reviews previous analyses and conclusions of others and discusses limitations to V/sub oc/. >

7 citations

01 Jan 2002
TL;DR: In this article, a wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogendilution during the growth of the i layer to arrive at theamorphous-to-microcrystalline phase transition region.
Abstract: High-voltage wide bandgap thin-film Si n-i-p solarcells have been made using the hot-wire chemical vapordeposition (HWCVD) technique. The best open-circuitvoltage (V oc ) has exceeded 0.94 V in solar cells usingHWCVD in the entire n-i-p structure. A V oc of 0.97V hasbeen achieved using HWCVD in the n and i layers andplasma-enhanced (PE) CVD for the p layer. The highvoltages are attributed to the wide-gap i layer and animproved p/i interface. The wide-gap i layer is obtained byusing low substrate temperatures and sufficient hydrogendilution during the growth of the i layer to arrive at theamorphous-to-microcrystalline phase transition region.The optical band gap (E 04 ) of the i layer is found to be 1.90eV. These high-voltage cells also exhibit good fill factorsexceeding 0.7 with short-circuit-current densities of 8 to 10mA/cm 2 on bare stainless steel substrates. We have alsocarried out photoluminescence (PL) spectroscopy studiesand found a correlation between V

2 citations

Proceedings ArticleDOI
19 May 2002
TL;DR: In this paper, a wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogen dilution during the growth of the i layer to arrive at the amorphous-to-microcrystalline phase transition region.
Abstract: High-voltage wide bandgap thin-film Si n-i-p solar cells have been made using the hot-wire chemical vapor deposition (HWCVD) technique. The best open-circuit voltage (V/sub oc/) has exceeded 0.94 V in solar cells using HWCVD in the entire n-i-p structure. A V/sub oc/ of 0.97 V has been achieved using HWCVD in the n and i layers and plasma-enhanced (PE) CVD for the p layer. The high voltages are attributed to the wide-gap i layer and an improved p/i interface. The wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogen dilution during the growth of the i layer to arrive at the amorphous-to-microcrystalline phase transition region. The optical band gap (E/sub o4/) of the i layer is found to be 1.90 eV. These high-voltage cells also exhibit good fill factors exceeding 0.7 with short-circuit-current densities of 8 to 10 mA/cm/sup 2/ on bare stainless steel substrates. We have also carried out photoluminescence (PL) spectroscopy studies and found a correlation between V/sub oc/ and the PL peak energy position.

2 citations


Cites background from "Effects of Carbon Grading at the p/..."

  • ...as a wide-gap a-SiC:H or a-SiO:H layer, hydrogen-diluted a-Si:H i layer near the amorphous-to-microcrystalline transition, or a wide-gap conductive H-diluted p layer, or using a microcrystalline p layer [4-7]....

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Book ChapterDOI
01 Jan 1995
TL;DR: In this paper, the optoelectronic properties of amorphous silicon using the plasma-enhanced chemical vapor deposition (PECVD) technique have been studied and an interdependence exists among crucial deposition parameters and their influence on the material properties and hence on the performance of the electronic devices.
Abstract: Publisher Summary The aim of this chapter is to study optoelectronic properties of amorphous silicon using the plasma-enhanced chemical vapor deposition (PECVD) technique. The most intensively studied of the amorphous semiconductor family is amorphous silicon (a-Si), and particularly the hydrogenated variety. Any deposition technique that does not employ a reactive environment of H (or F) leads to extremely poor materials in terms of high density of localized states (DOS) due to Si dangling bonds, such that the films cannot be electronically doped, which then precludes any electronic device possibilities. Numerous techniques for depositing a-Si-based alloys have been attempted, plasma-enhanced chemical vapor deposition (PECVD) in SiH4 gas, PECVD in SiF4 and H2 gas mixtures, reactive sputtering of Si in H environments, evaporation of Si in the presence of H, CVD of SiH4 gas and higher silanes, photo-CVD, electron cyclotron resonance (ECR) PECVD, and remote PECVD. This chapter attempts to show that an interdependence exists among crucial deposition parameters and their influence on the material properties and hence on the performance of the electronic devices. Amorphous silicon technology has now matured to the point where many products are now commercially available.

2 citations

01 May 2002
TL;DR: In this paper, a wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogen dilution during the growth of the i layer to arrive at the amorphous-to-microcrystalline phase transition region.
Abstract: High-voltage wide bandgap thin-film Si n-i-p solar cells have been made using the hot-wire chemical vapor deposition (HWCVD) technique. The best open-circuit voltage (Voc) has exceeded 0.94 V in solar cells using HWCVD in the entire n-i-p structure. A Voc of 0.97V has been achieved using HWCVD in the n and i layers and plasma-enhanced (PE) CVD for the p layer. The high voltages are attributed to the wide-gap i layer and an improved p/i interface. The wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogen dilution during the growth of the i layer to arrive at the amorphous-to-microcrystalline phase transition region. The optical band gap (E04) of the i layer is found to be 1.90 eV. These high-voltage cells also exhibit good fill factors exceeding 0.7 with short-circuit-current densities of 8 to 10 mA/cm2 on bare stainless steel substrates. We have also carried out photoluminescence (PL) spectroscopy studies and found a correlation between Voc and the PL peak energy position.
References
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Journal ArticleDOI
TL;DR: In this article, a novel structure, high conversion efficiency amorphous silicon (a•Si)/metal substrate-type solar cell has been developed, deduced from the conventional pin junction by the use of a gradual compositional grading p•type a•SiC:H layer between an ultrathin (∼20 A) wide optical band gap (√2.4 eV) p• type a• SiC:C layer and the i layer, exhibits markedly enhanced opencircuit voltage (Voc) and shortcircuit current density (Isc) over
Abstract: A novel structure, high conversion efficiency amorphous silicon (a‐Si)/metal substrate‐type solar cell has been developed. The new structure, deduced from the conventional pin junction by the use of a gradual compositional grading p‐type a‐SiC:H layer between an ultrathin (∼20 A) wide optical band gap (∼2.4 eV) p‐type a‐SiC:H layer and the i layer, exhibits markedly enhanced open‐circuit voltage (Voc) and short‐circuit current density (Isc) over the conventional a‐Si pin/substrate‐type solar cell. Especially, the collection efficiency in the newly developed structure was found to be remarkably increased at short wavelengths. The experimentally observed improvement in the blue response is due to the reduction in effective interface recombination combined with the enhanced window effect. An energy conversion efficiency of 8.40% under air mass (AM) 1 (100 mW/cm2) illumination has been obtained in the first trial of a cell fabricated by the rf glow discharge decomposition of pure silane (SiH4).

70 citations

Journal ArticleDOI
TL;DR: In this article, a new type of amorphous silicon solar cell having a conversion efficiency of 8% level is introduced, which has a wide band gap window layer made of hydrogenated amorphized silicon carbide, with a good valency control.
Abstract: A new type of amorphous silicon solar cell having a conversion efficiency of 8% level is introduced. The cell has a wide band gap window layer made of hydrogenated amorphous silicon carbide, (a-SiC:H), with a good valency control. Electrical, optical and optoelectronic properties of a-SiC:H have been investigated, together with their valency controllability. A design concept and some key technologies to improve solar cell performance with this new material are demonstrated. A series of technical data on material preparation and cell performance are presented. Clear improvements in cell performance, not only IDC but also VDC, have been obtained. The realistic limit of the conversion efficiency in a-Si solar cells is estimated and discussed.

45 citations

Journal ArticleDOI
TL;DR: In this article, the interfaces between hydrogenated amorphous silicon carbon alloy and polysilicon, both hydrogenated and not, were investigated by photoemission spectroscopy.
Abstract: The interfaces between hydrogenated amorphous silicon‐carbon alloy and amorphous silicon, both hydrogenated and not, were investigated by photoemission spectroscopy. It is found that the valence‐band discontinuity is 0.15±0.1 eV for the amorphous Si case and zero within the experimental uncertainty for the hydrogenated amorphous Si. The relevance of this result for understanding the behavior of the p‐i‐n amorphous solar cells is discussed.

29 citations

Journal ArticleDOI
TL;DR: In this article, a computer model based on the solution of the complete set of transport equations was used to investigate electric field profiles, carrier distributions and the open-circuit voltage of amorphous silicon-based alloy p-i-n solar cells illuminated through either the p+ or n+ layer.
Abstract: Using a computer model based on the solution of the complete set of transport equations we have investigated electric field profiles, carrier distributions and the open‐circuit voltage of amorphous silicon‐based alloy p‐i‐n solar cells illuminated through either the p+ or n+ layer. Our results indicate that even with a large difference in the electron and hole band mobilities there is no large difference (<50 mV) in the open‐circuit voltage for the two cases. This difference is small because for optimized devices the open‐circuit voltage is limited by the recombination current which is relatively insensitive to space charge and Dember effects. We also show that boron doping in the intrinsic layer can drastically alter the electric field profile in these devices, and can increase the open‐circuit voltage of p‐i‐n solar cells with low built‐in potentials.

18 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that boron carryover into the i layer is responsible for the commonly observed difference in open circuit voltage between p i n and n i p amorphous silicon solar cells.
Abstract: Data are presented showing that boron carryover into the i layer is responsible for the commonly observed difference in open circuit voltage between p‐i‐n and n‐i‐p amorphous silicon solar cells. It is proposed that the lower voltage samples are being limited by surface recombination at the p/i interface and that boron carryover reduces this recombination current. The Voc is then able to rise to the point where it is limited by the bulk recombination current.

10 citations