Emmanuel Van Kerschaver

Comparison of n- and p-type high efficiency silicon solar cell performance under low illumination conditions

For scavenging energy out of the environment, it is very important for solar cells to maintain the efficiency at low light intensity levels. The high efficiency p-type front junction (18.3% at 1 sun AM1.5) and n-type rear junction (17.3% at 1 sun AM1.5) cells are prepared using an identical cell process based on firing an aluminum paste on the rear. The Al paste acts either as back surface field or rear emitter respectively. A detailed characterization of these cells under low illumination conditions was carried out based on the measured efficiency and suns-Voc. In this paper, it is experimentally and theoretically shown that n-type base cells outperform p-type base cells at such low injection levels. The observed dependence of the performance on the injection level is explained using the Shockley-Read-Hall recombination model where the different capture cross sections for electrons and holes has a decisive influence on the minority carrier bulk lifetime for p-type silicon under low level injection.

All-aluminum screen-printed IBC cells: Design concept

A design concept supported by numerical device modeling is presented for a p-type IBC cell with screen-printed aluminum for both contact polarities. Applying such a design to Cz silicon appears to offer cell efficiency exceeding 20%. The key enabling feature for this design is cleaving each cell into strips held together by tape. These strips are then connected electrically in series using extrusion printing after the strips are laminated to the module glass. The resulting module technology is called SPLICE, for “Screen Printed Locally Interdigitated Contact Elements”.

A DLTS Study of SiO2 and SiO2/SiNx Bi-Layer Surface Passivation of Silicon

Deep Level Transient Spectroscopy (DLTS) has been applied to Metal-Oxide-Semiconductor (MOS) capacitors fabricated on crystalline silicon n- and p-type substrates, with a SiO2 or a SiO2/SiNx bi-layer passivation stack, covered by an Al gate. It is shown that similar interface state distributions are obtained in both cases, from which it is concluded that the SiNx deposition does not degrade the interface. It is also shown that a rather large density of dangling bond defects is present at the Si/SiO2 interface, which is related to the absence of a post metallization forming gas annealing.

Bulk Passivation of Defects in Multi-Crystalline Silicon Solar Cells by a-SiNx:H Layers

In this work the impact of hydrogenation from hydrogen-rich amorphous silicon nitride (a-SiNx:H) on dislocations and grain boundaries in multi-crystalline silicon (mc-Si) solar cells is presented. Layers are deposited by means of plasma enhanced chemical vapor deposition (PECVD). Electrical bulk passivation is provided during thermal annealing, in which hydrogen diffuses from a-SiNx:H. The passivation effect is discussed in terms of recombination centers and non-recombinative charge traps reduction as well as in terms of local short circuit current improvement in specially manufactured solar cells.

Laser sintering of screen-printed silver paste for silicon solar cells

This paper proposes laser sintering of screen-printed silver grids, which is compatible with low temperature surface passivation materials such as intrinsic hydrogenated amorphous silicon and has the potential of fabricating high efficiency solar cells at a low cost. It was found that a nanosecond pulsed laser (λ = 532 nm) can locally and controllably fire silver paste through SiNx without punching through the underneath phosphorus-diffused emitter. A low temperature belt firing prior to laser sintering is helpful for improving the quality of laser sintering. Laser sintered cells reached 17.3% cell efficiency on 239 cm2 cell area.