Solar energy could become more affordable following a breakthrough by UNSW scientists, who have boosted the efficiency of solar cell technology.

The advance could see the price of an installed solar system for an average house fall from around $20,000 to $15,000. Up to 45 percent of the cost of solar cell technology is due to the high cost of the silicon used to convert sunlight to electricity.

Silicon is the material of choice in the electronics industry because of its stability, non-toxicity and ubiquity. However, silicon is a poor absorber of light. In a bid to drive down costs, scientists have moved from using expensive thick silicon “wafers” to cheaper “thin film” cells, containing less silicon.

The disadvantage of these one-to-two micron-thick films is that they convert only eight to 10 percent of incoming sunlight into electricity, compared to the 25 percent efficiency of thicker, more expensive, silicon wafers. Scientists around the world are testing new ways to boost the efficiency of thin film technology, while keeping down costs.

Now, researchers at UNSW’s ARC Photovoltaics Centre of Excellence, led by PhD student Supriya Pillai have reported a 16-fold enhancement in light absorption in 1.25-micron thin-film cells for light with a wavelength of 1050 nm. They have also reported a seven-fold enhancement in light absorption in the more expensive wafer type cells light wavelengths of 1200 nm.

"Most thin-film solar cells are between eight and 10 percent efficient," says Dr Kylie Catchpole, a co-author of the study, "but the new technique could increase efficiency to between 13 and 15 percent."

That's an important advance, she says: "If they're below 10 percent efficient, then you can't really afford to install them, because it would take up too much of your roof area, for example, to power your house." Once the technology approaches 15 per cent efficiency, it becomes commercially viable.

An average house could have its daily power supplied by installing a solar system and panels covering 10 square metres. This system would exclude power for cooking and hot water heating.

The breakthrough, which is reported in the upcoming issue of the Journal of Applied Physics, could eventually see a dramatic rise in solar power’s share of the electricity market. Currently only 30,000 Australian households - out of 8 million - have installed solar panels.

The UNSW researchers have devised a way to deposit a thin film of silver (about 10 nanometres thick) onto a solar cell surface and then heat it to 200° Celsius. This breaks the film into tiny 100-nanometre “islands” of silver that boost the cell’s light trapping ability, thereby boosting its efficiency.

效能的提高增强了对太阳能电池的购买承受力

随着新南威尔士大学（UNSW）科学家们提高了太阳能电池工艺的效能，这一突破有可能使太阳能的使用成本更加低廉。

这一改进从一种太阳能系统安装的费用自约$20,000降至$15,000可见一斑。高至45%太阳能电池工艺的成本是由于制作一种能够把光能转化成电能的硅片装置。

由于其稳定、无毒和分布广泛的特性，硅是被电子制造业广泛采用的一种原料。尽管如此，硅也是一种吸光能力很差的元素。因此为了节约成本，科学家们已从原来使用昂贵的厚硅晶片转移至更廉价的含较少量硅的薄膜电池。

这种只有1-2微米厚的硅膜层的主要缺点就是它们只能将所进入阳光的10%转变成为电能，相对更厚而价格昂贵硅晶则拥有25的转化率。目前世界上的科学家们正在测试新的方法在压低成本的同时提高薄膜层工艺效能。

目前，由在读博士生Supriya Pillai 所带领的UNSW ARC卓越光电中心的研究者们报告说发现在1050 纳米波长光处1.25微米的薄硅膜对光的吸收出现16倍的增长。同时他们还发现更昂贵的硅晶型电池在1200纳米波长处的吸光度可有7倍的增长。

“大多数薄层太阳能电池的效能在8-10%之间，”这项研究的合著者Kylie Catchpole博士说到：“但是我们利用最新的技术可以使效能提高到13-15%之间。”

那将是一项重要的进步，她说到：“如果它们的效能在10%以下，那么安装将使你遇到无法承受的困难，因为它将占据你屋顶的绝大面积。例如，是你的整个房子带电。”一旦先进的工艺能够使效能提高到15%，它将变得经济而可行。

只需安装一个10平米面积的太阳能控板即可供给一般大小房屋的日常用电，包括烹饪和烧水所需的电力。

这项被刊登在应用物理学期刊突破，将最终刺激电力市场的太阳能份额出现戏剧性飙升。当前8百万澳洲居民中只有30,000家安装了太阳能控板。

UNSW的研究者们设计了一种将一层极薄的银膜（约10纳米厚）放置太阳能电池表面随之加热其至200°摄氏度，这致使银薄膜裂分成能够提高了电池的捕光能力的100纳米碎片，从而增强了其效能。