English:
[0001] The present invention relates generally to solar cells and, in particular, to an improved structure and manufacturing process for a bifacial solar cell.
[0002] Bifacial solar cells (BSC) may use any of a variety of different designs to achieve higher efficiencies than those typically obtained by a conventional, monofacial solar cell. One such design is shown in U.S. Patent No. 5,665,175 which discloses a BSC configuration with first and second active regions formed on the front and back surfaces of the BSC, respectively, the two regions separated by a distance λ. The distance λ allows a leakage current to flow between the first and second active regions, thus allowing a solar cell panel utilizing such bifacial cells to continue to operate even if one or more individual solar cells become shaded or defective.
[0003] U.S. Patent No. 7,495, 167 discloses an n+pp+structure and a method of producing the same. In the disclosed structure, the p+layer, formed by boron diffusion, exhibits a lifetime close to that of the initial level of the substrate. In order to achieve this lifetime, the ' 167 patent teaches that after phosphorous gettering, the cell must be annealed at a temperature of 600° C or less for one hour or more. In order to retain the lifetime recovered by the phosphorous and low-temperature born gettering steps, the cell then undergoes a final heat treatment step in which the cell is fired at a temperature of around 700° C or less for one minute or less.
[0004] U.S. Patent Application Publication No. 2005/0056312 discloses an alternative technique for achieving two or more p-n junctions in a single solar cell, the disclosed technique using transparent substrates (e.g., glass or quartz substrates). In one disclosed embodiment, the BSC includes two thin-film polycrystalline or amorphous cells formed on opposing sides of a transparent substrate. Due to the design of the cell, the high temperature deposition of the absorber layers can be completed before the low temperature deposition of the window layers, thus avoiding degradation or destruction of the p-n junctions.
[0005] Although there are a variety of BSC designs and techniques for fabricating the same, these designs and techniques tend to be relatively complex, and thus expensive. Accordingly, what is needed is a solar cell design that achieves the benefits associated with bifacial solar cells while retaining the manufacturing simplicity of a monofacial solar cell. The present invention provides such a design.
[0009] Fig. 1 illustrates a preferred embodiment of a BSC in accordance with the invention;
[0010] Fig. 2 illustrates the process flow for the BSC of Fig. 1 ; and
[0011] Fig. 3 illustrates an alternate process flow for the BSC of Fig. 1.

中文:
[0001]本发明总体上涉及太阳能电池,更具体地,涉及用于双面太阳能电池的改进结构和制造工艺。
[0002]双面太阳能电池(BSC)可应用任何种类不同的设计来获得比传统单面太阳能电池通常所获得的效率更高的效率。这种设计之一参见美国专利5,665,175,其公开了具有分别形成于BSC的前表面和后表面的第一活动区(active region)和第二活动区的BSC结构,这两个区分开距离λ。距离λ使得泄露电流在所述第一和第二活动区之间流动,因此使得利用这样的双面电池的太阳能电池板即便在一个或多个个别的太阳能电池被遮蔽或有缺陷时还能够继续工作。
[0003]美国专利7,495,167公开了一种n+pp+结构,以及一种制造该结构的方法。在所公开的结构中,由硼扩散形成的p+层的寿命接近于衬底的初始水平。为了获得该寿命,美国专利7,495,167教示了磷吸杂之后,电池必须在600°C或更低的温度下退火一小时或更长时间。然后,为了保持通过磷和低温硼吸杂步骤恢复的寿命,电池经受最后的热处理步骤,其中将电池在大约700°C或更低的温度下烧制(fire)一分钟或更短时间。
[0004]美国专利申请公开2005/0056312公开了用于在单个太阳能电池中获得两个或更多个p-n结的可选技术,所述公开的技术采用了透明衬底(例如玻璃或石英衬底)。在一个公开的实施例中,BSC包括形成在透明衬底的相对侧的两个薄膜多晶或非晶电池。由于该电池的设计,可在窗口层的低温沉积之前完成吸收器层的高温沉积,因此可避免p-n结的退化或破坏。
[0005]尽管存在多种用于制造BSC的BSC设计和技术,这些设计和技术倾向于相对复杂,且因此昂贵。因此,需要一种太阳能电池设计,能够获得与双面太阳能电池相关的优点,同时保持单面太阳能电池的制造简单性。本发明将提供这样的设计。
[0009]图1描述了根据本发明所述的BSC的优选实施例;
[0010]图2描述了用于图1的BSC的方法流程;以及
[0011]图3描述了用于图1的BSC的可选方法流程。