L. Carnel
Katholieke Universiteit Leuven
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by L. Carnel.
Applied Physics Letters | 2007
D. Van Gestel; Manuel J. Romero; Ivan Gordon; L. Carnel; J. D’Haen; Guy Beaucarne; Mowafak Al-Jassim; J. Poortmans
Defect etching revealed a very large density (∼109cm−2) of intragrain defects in polycrystalline silicon (pc-Si) layers obtained through aluminum-induced crystallization of amorphous Si and epitaxy. Electron-beam-induced current measurements showed a strong recombination activity at these defects. Cathodoluminescence measurements showed the presence of two deep-level radiative transitions (0.85 and 0.93eV) with a relative intensity varying from grain to grain. These results indicate that the unexpected quasi-independence on the grain size of the open-circuit voltage of these pc-Si solar cells is due to the presence of numerous electrically active intragrain defects.
Journal of Applied Physics | 2006
L. Carnel; Ivan Gordon; D. Van Gestel; Guy Beaucarne; J. Poortmans; Andre Stesmans
Grain boundaries are known to be the main limiting factor for a high performance of polysilicon solar cells. Defects at these grain boundaries serve as recombination centers for minority and majority carriers. Grain boundaries are also known to be paths for enhanced hydrogen diffusion, which results in passivation of part of the defects. In this paper, we show that grain boundaries are also paths for an enhanced phosphorus diffusion that limits the effect of hydrogen passivation. Phosphorus spikes along the grain boundaries enhance the junction area and determine the collection and the recombination volumes. Avoiding this preferential diffusion of phosphorus atoms during emitter formation, we obtained open-circuit voltages (Voc) up to 536mV on polysilicon material with a grain size of only 0.2μm. These high Voc values can only be accounted for by theory if a much smaller grain boundary recombination velocity is assumed than what was previously accepted for p‐n junctions on fine-grained polysilicon solar c...
IEEE Electron Device Letters | 2006
L. Carnel; H.F.W. Dekkers; Ivan Gordon; D. Van Gestel; K. Van Nieuwenhuysen; Guy Beaucarne; J. Poortmans
A considerable cost reduction in photovoltaics could be achieved if efficient solar cells could be made from thin polycrystalline-silicon (pc-Si) films. Although hydrogen passivation of pc-Si films is crucial to obtain good solar cells, the exact mechanism of hydrogen diffusion through pc-Si layers is not yet understood. In this letter, the influence of the junction and the grain size are investigated. We find that the presence of a p-n junction acts as a barrier for hydrogen diffusion in thin-film polysilicon solar cells. Therefore, pc-Si solar cells should preferably be passivated before junction formation. Furthermore, pc-Si layers with large grains retain less hydrogen after passivation than layers with small grains. This indicates that hydrogen atoms get mainly trapped at the grain boundaries.
ieee world conference on photovoltaic energy conference | 2006
L. Carnel; Ivan Gordon; Dries Van Gestel; Linda R. Pinckney; Alexandre Michel Mayolet; Jan D'Haen; Guy Beaucarne; J. Poortmans
Thin-film polysilicon solar cells on foreign substrates are often considered as a promising low cost alternative to bulk silicon solar cells. Until now however, the obtained efficiencies and open-circuit voltages are far below those of other technologies. In this paper, we show how the open-circuit voltage can be enhanced significantly using an amorphous silicon-crystalline silicon heterojunction emitter instead of a diffused homojunction emitter. Open-circuit voltages up to 536 mV were obtained for polysilicon layers with a heterojunction emitter. This is the highest open-circuit voltage obtained for polysilicon solar cells with a p-n structure on foreign substrates
IEEE Electron Device Letters | 2007
L. Carnel; Ivan Gordon; D. Van Gestel; D. Vanhaeren; Pierre Eyben; Guy Beaucarne; J. Poortmans
Thin-film polysilicon solar cells are a promising low-cost alternative for bulk silicon solar cells due to their reduced material thickness. Recently, we showed that the use of an amorphous silicon/polycrystalline silicon heterojunction emitter instead of a diffused homojunction emitter led to a boost in the open-circuit voltage by 90 mV. Now, we present a full evidence that shows that this improvement is related to the absence of dopant smearing along the grain boundaries. By using scanning spreading resistance microscopy, we found an enlargement of the junction area by a factor of five in case of a homojunction. The tips of the dopant spikes represent lowly doped areas with an enhanced recombination.
MRS Proceedings | 2007
Dries Van Gestel; Ivan Gordon; L. Carnel; Guy Beaucarne; Jef Poortmans
To reduce the harmful influence of grain boundaries in polycrystalline Si layers we make absorber layers on foreign substrates with columnar grains with a grain width larger than the grain thickness. Such layers with a grain size in the range of ~1-100 µm can be obtained by aluminum-induced crystallization and epitaxy. Until now however, the open-circuit voltage of solar cells made from such layers was quasi-independent of the grain size. To understand this fact, defect etching and Electron Backscattered diffraction (EBSD) measurements were performed to investigate the crystallographic defects. A very large density (~ 10 9 cm -2 ) of intra-grain defects (IGD) was found. Room temperature Electron Beam Induced Current (EBIC) measurements were done to localize and investigate the electrically active defects. The intra-grain defects found with defect etching showed a strong recombination activity. These results indicate that the unexpected quasi-independence on the grain size of the open-circuit voltage of our pc-Si solar cells is due to the presence of numerous electrically active intra-grain defects.
Progress in Photovoltaics | 2007
Ivan Gordon; L. Carnel; D. Van Gestel; Guy Beaucarne; J. Poortmans
Thin Solid Films | 2005
Ivan Gordon; D. Van Gestel; K. Van Nieuwenhuysen; L. Carnel; Guy Beaucarne; J. Poortmans
Thin Solid Films | 2008
Ivan Gordon; L. Carnel; D. Van Gestel; Guy Beaucarne; J. Poortmans
Thin Solid Films | 2006
L. Carnel; Ivan Gordon; D. Van Gestel; K. Van Nieuwenhuysen; G. Agostinelli; Guy Beaucarne; J. Poortmans