Amorphous silicon p-i-n solar cell.

p0001The invention relates to a solar cell with an existing, preferably of tin oxide-indium oxide anti-reflection layer and an existing amorphous silicon semiconductor body, which contains between a p-type region and an n-type zone have an intrinsic (i) layer that a decreasing in the direction of in-transition Bordotierungsprofil having.

p0002Such solar cells are both from J. Appl. Phys. 54 (11) pages 6705-6707 and from Appl. Phys. Letters 44 (11) pages 1092-1094 known. By Bordotierungsprofil in the i-layer is achieved that a high efficiency of up to 9.45% and good fill factors of 0.72 are obtained. The cells are formed on glass substrates, and the light is irradiated from the p-side.

p0003In thin-film solar cells made from amorphous silicon (a-Si) with the layer sequence pin, the light can be irradiated by both the p-side and the n-side. These cells show more or less pronounced so-called Staebler-Wronski effect. Due to this effect, in lighting, especially when the cell is operated open, ie bears the open circuit voltage, a reversible decrease in the efficiency of, for example, up to 50% at an illumination of 100 mW / cm² take place with a time duration of 16 hours. Reversible here means that by tempering the arrangement with, for example, 180^*C after 30 minutes, the output values ​​of the efficiency can be reached again. Although the decrease in the efficiency decreases with time, such cells are of limited use for industrial use.

p0004The object of the invention is therefore to prevent the photoaging just described and a stable to create the Staebler-Wronski effect not having solar cell.

p0005This object is achieved by a solar cell of the type mentioned, which is characterized according to the invention by the following structure:<ul><li>a), consisting of metal back contact electrode,</li><li>b) the one on the rear side contact electrode applied as the substrate body of the amorphous semiconductor layer sequence pin,</li><li>c) deposited on the semiconductor body antireflection layer constituting the upper electrode, and</li><li>d) a, applied to the anti-reflective layer, serving as a front side contact metal strip electrode system.</li></ul>

p0006It is within the scope of the invention that the boron concentration in the pi-transition is 40 ppm in the amorphous silicon (a-Si) and decreases to zero at the in-transition. A corresponding Borkonzentrationsgradient adjusts to the amorphous silicon. As the intrinsic layer is formed in a separate glow discharge deposition, precipitated by this measure, the carry-over of boron no longer significant. In reaction gas of boron is at 20 ppm diborane (B₂H₆) With respect to the reaction gas of silane (SiH₄) Set.

p0007Further embodiments of the invention result from the dependent claims.

p0008The invention is explained below with reference to Figures 1 and 2 in more detail. It shows<ul><li>Figure 1 schematically illustrates the structure of the solar cell with the adjacent, for example, linear and Bordotierungsprofil</li><li>Figure 2 a graph showing the decrease in the efficiency (-Δη) in percent (ordinate) by a 16-hour 100 mW / cm^2-Lighting without load resistor (Staebler-Wronski effect) as a function of the boron concentration; (The abscissa shows the initial value of the pi-transition of diborane in the silane).</li></ul>

p0009In figure 1 the following reference numerals are:<ul><li>1 = substrate body, for example, stainless steel,</li><li>2 = amorphous silicon layer is p-doped (20 nm),</li><li>3 = intrinsic amorphous silicon layer with boron profile (500 nm),</li><li>4 = amorphous silicon layer n-doped (15 nm),</li><li>5 = indium-tin oxide layer (ITO =, anti-reflection layer, 70 nm)</li><li>6 = metal strip system consisting of a chromium-nickel alloy, an existing, for example, silver intermediate layer and a layer of tin</li><li>7 = direction of the incident rays (hv).</li></ul>

p0010As can be seen from Figure 2, shows the light aging of cells without load resistance and the linear Bordotierungsprofil in the intrinsic layer only changes the efficiency η in the range of measurement accuracy (absolute deviation: approximately + 0.1%).

p0011Although the efficiency is not as high as that of the aforementioned cells; the stability of the cells of the invention is compared to the known arrangements but much better.