双语阅读｜新太阳能板材料有望替代硅

SOMETIMES it takes a while for the importance of a scientific discovery to become clear. When the first perovskite, a compound of calcium, titanium and oxygen, was discovered in the Ural mountains in 1839, and named after Count Lev Perovski, a Russian mineralogist, not much happened. The name, however, has come to be used as a plural to describe a range of other compounds that share the crystal structure of the original. In 2006 interest perked up when Tsutomu Miyasaka of Toin University in Japan discovered that some perovskites are semiconductors and showed particular promise as the basis of a new type of solar cell.

有时候，科学发现的重要性需要经过一段时间才能显现出来。1839年，在乌拉尔山脉发现第一块钙钛氧化合物钙钛矿，并以俄罗斯矿物学家列夫·佩洛夫斯基伯爵的名字命名。然而，这个名称用于描述众多有相同晶体结构的化合物。2006年，日本桐荫横滨大学Tsutomu Miyasaka发现一些钙钛矿是半导体材料，而且有可能作为新型太阳能电池主要成分。这个发现让人们对钙钛矿的兴趣大增。

In 2012 Henry Snaith of the University of Oxford, in Britain, and his colleagues found a way to make perovskite solar cells with an efficiency (measured in terms of how well a cell converts light into electric current) of just over 10%. This was such a good conversion rate that Dr Snaith immediately switched the direction of Oxford Photovoltaics, a firm he had co-founded to develop new solar materials, into making perovskites—and perovskites alone. Progress has continued, and now that firm, and also Saule Technologies, a Polish concern founded in 2014 to do similar things, are close to bringing the first commercial perovskite solar cells to market.

2012年，英国牛津大学的亨利·斯奈斯及其同事发现一种制造出钙钛矿太阳能电池的方法，效率(以电池将光转化为电流的能力来衡量)略高于10%。这种转化率相当不错，因此，斯奈斯博士立即改变其共同创立的牛津太阳光电公司的发展方向，从原来的开发新的太阳能材料转而只生产钙钛矿。对于钙钛矿的研发还在继续。现在，该公司与2014年成立的波兰Saule Technologies公司都开始做类似的事情，同时，他们即将要第一批商用钙钛矿太阳能电池推向市场。

Today 10% is quite a modest efficiency for a perovskite cell in the coddling conditions of a laboratory. For lab cells values above 22% are now routine. That makes those cells comparable with ones made from silicon, as most of the cells in solar panels are—albeit that such silicon cells are commercial, not experimental. It did, however, take silicon cells more than 60 years to get as far as they have, and the element is probably close to its maximum practical level of efficiency. So, there may not be much more to squeeze from it, whereas perovskites could go much higher.

如今，对于钙钛矿电池在尚未成熟的实验室条件来说，10％的效率是相当不错的。对于实验室级别的电池来说，常规的转化率是22%以上。这就使得电池与硅电池具有可比性，因为太阳能电池板上的大多数电池都是商用级的，而非用于实验级别的。然而，硅电池经过60多年发展才达到目前的水平，而且这种元素可能接近其实际效率的最高水平。因此，可能没有更多的发展空间了，而钙钛矿可以更大的发展空间。

Perovskite cells can also be made cheaply from commonly available industrial chemicals and metals, and they can be printed onto flexible films of plastic in roll-to-roll mass-production processes. Silicon cells, by contrast, are rigid. They are made from thinly sliced wafers of extremely pure silicon in a process that requires high temperature. That makes factories designed to produce them an expensive proposition.

钙钛矿电池还可以从常规的工业化学品和金属中制造出来，成本低廉，能投放的大规模生产过程中使用，印刷到塑料的柔性薄膜上。相比之下，硅电池较坚硬，是由极纯的硅片薄片经过高温制成的，使得工厂的生产成本高昂。

Racing with silicon

与硅的角逐

On the face of it, then, perovskites should already be transforming the business of solar power. But things are never that simple. First, as with many new technologies, there is a difference between what works at small scale in a laboratory and at an industrial scale in a factory. Learning how to manufacture something takes a while. Also, perovskites as materials are not without their problems—in particular, a tendency to be a bit unstable in high temperatures and susceptible to moisture, both of which can cause the cells to decompose. Such traits are unconducive to the success of a product that would be expected to last two or three decades in the open air. Researchers are beginning to solve those shortcomings by making perovskites that are more robust and waterproof.

从表面上看，钙钛矿应该改变了太阳能产业，而事情远没有那么简单。首先，与许多新技术一样，在实验室小规模生产与在工厂大规模生产是有区别的。要实现批量生产还需要一段时间。此外，钙钛矿作为一种材料也存在一些问题——尤其的是，它在高温下不太稳定，而且容易受潮，这两种情况都会导致电池分解。这些特点不利于产品的成功，因为这种产品预计在户外可使用二三十年。目前，研究人员正着手解决这些不足之处，制造出更坚固、更防水的钙钛矿。

But even if they succeed, there is a third consideration. This is that these newfangled cells will have to go up against an incumbent solar-power industry which invested $160bn in 2017 and is familiar with silicon and how to handle it.

但是，即使上述两个问题解决了，还有第三个需考虑的因素，即这个新材料电池必须与现有的太阳能产业角逐——2017年有1600亿美元投资，熟悉了解硅，有成熟的方案。

What perovskites need, then, is a record which would provide that industry with the confidence to use them. To do this, both Oxford Photovoltaics and Saule are teaming up with large companies to ease the new materials into the market quite literally on the back of established products.

此外，钙钛矿需要的是记录工业使用这些产品的信心。为了做到这一点，牛津光电公司和萨勒公司正与大公司合作，让新材料在现有产品的支持下可以轻松进入市场。

In the case of Oxford Photovoltaics those established products are existing silicon solar cells. The idea behind the resulting so-called tandem cells is that

together the two materials involved can mop up more of the spectrum and turn it into electricity. This is done by tweaking the perovskite upper layer to absorb strongly at the blue end of the spectrum and leaving the lower silicon layer to capture those wavelengths falling towards the red end. That boosts the efficiency of the combined panel by 20-30% says Frank Averdung, Oxford Photovoltaics’ boss. Tandem cells of this sort would allow solar-panel producers to offer a performance beyond anything silicon alone might achieve. Such panels would, of course, cost more to make—but the boost in performance will not, Mr Averdung says, increase the cost per watt and in time may reduce it.

以牛津光伏公司为例，这些已有的产品是以硅太阳能电池形态出现。这种所谓的串联电池的原理是，将两种材料结合在一起，吸收更多的光谱转化为电能。这是通过调整钙钛矿的上层来强烈吸收光谱的蓝色端，并留下较低的硅层来捕捉那些向红色端下降的波长。牛津光伏公司的老板Frank Averdung表示，这种复合板能将效率提高20-30%。这种串联电池能让太阳能电池板制造商提供一种硅材料无法匹敌的性能。当然，这种电池板的制造成本会更高，但性能的提升不会增加每瓦成本，假以时日还能降低成本。

Oxford Photovoltaics is now building a production line in Germany to start making tandem cells next year with what it describes as standard industrial processes. The factory will be used to demonstrate the technology, which will then be licensed to other manufacturers. Some of the details are still secret, because the company is working with a large but unnamed solar-energy firm.

目前，牛津光伏正在德国建立一条生产线，在明年开始生产串联电池。该公司称这条生产线标准工业流程。这家德国工厂会用来展示这项太阳能技术；该技术之后会许可给其它制造商。由于该公司正在与一家大型太阳能企业合作，该技术的一些细节仍处于保密状态。

The tandem approach lowers the barrier to perovskites entering the market, and allows the new materials to be shown to meet various industry standards. It is, though, intended only as a halfway house. Eventually, Mr Averdung believes, perovskites will act as stand-alone cells—and not just in conventional panels. Because they are semi-transparent, perovskite films could also be used to turn windows into solar generators, by capturing part of the incoming sunlight while permitting the rest to pass through.

串联法减少了钙钛矿进入市场的障碍，并让这些新材料满足各行各业的标准。不过，这仅仅是一个折中办法。最终，Averdung认为，钙钛矿将作为独立电池——而不仅仅是传统面板。由于是半透明的，钙钛矿薄膜也可吸入一部分光源，同时滤过其它部分，从而将窗户变成太阳能发电机。

Saule, meanwhile, is using inkjet printing to produce its own perovskite cells on thin plastic sheets. At present it can turn these out in A4 size (210mm by 297mm), but it is scaling up the process to manufacture versions with an area of one square metre. Saule’s sheets have an efficiency of 10%, so are not yet a match for the sorts of silicon panels found in solar farms. But Artur Kupczunas, a co-founder of the company, says that in combination with the cheapness, flexibility and lack of weight of perovskite sheets, an efficiency of 10% is enough to justify applying those sheets to the exteriors of buildings. The established products that Saule is hoping to ride on the back of are thus the components used to construct those exteriors.

与此同时，Saule公司使用喷墨印刷技术在薄塑料上生产自己的钙钛矿电池。目前，该公司能出生产A4大小（210mm×297mm）的电池板，不过，它正在扩大工艺，生产面积为1平方米的电池。 Saule的板材效率达到了10％，与太阳能场中的各种硅板无法媲美。不过，该公司的联合创始人Artur Kupczunas表示，钙钛矿板有廉价，灵活和轻便的特点，10％的效率足以让将板材用在建筑外墙面。因此，Saule公司希望这些已面市场产品将来能用于作外部饰部件。

The power of the press

竞争压力的力量

To this end, Saule has granted Skanska, one of Europe’s biggest construction groups, the right to incorporate perovskite printed sheets into some of its components, such as those used to make façades. This would let the walls generate electricity, thus lowering a building’s carbon footprint and making it more self-sufficient. Skanska plans to test the sheets on an office block, possibly in Poland, later this year.

为此，Saule公司授权欧洲最大的建筑集团公司之一的Skanska，将钙钛矿印刷板用作建筑材料组件，用于如外墙建造方面。这能让墙壁发电，降低建筑物的碳足迹，能提升能源自给自足能力。Skanska公司计划于今年能在波兰的一个办公区实验这种太阳能板。

As the sheets would be added to their substrates off-site, there would, Mr Kupczunas points out, be no additional installation costs. In time, he expects sheets’ efficiencies to increase towards the 26% which the company has achieved in laboratory conditions. The printing process also makes it easy to produce sheets of different sizes for different applications. They should function better than silicon in low light, which means they would generate more electricity on cloudy days.

Kupczunas指出，由于太阳能板会不用在现场加装到基建材料上，无需额外的安装费用。他预计，随着时间的推移，板材的效率将提高到在实验室条件下的26％。印刷过程还可轻易生产出不同尺寸，适合不同场景的板材。它们在低光照条件下的反应好于硅，这意味着在阴天生产更多电。

Perovskites are thus now serious challengers to silicon solar cells. That does not mean they will succeed. The history of technology, in this area and in others, is littered with ideas that looked good (and, indeed, were often technically superior to existing alternatives) but nevertheless fell by the wayside. The power of incumbency should not be underestimated. And the price of silicon-based solar power has dropped markedly over the past decade, particularly as a consequence of enormous investment by the Chinese.

因此，对于硅太阳能电池来说，钙钛矿如今正式发起了挑战。这并不意味着他们会成功。无论是在技术史上还是其他领域，都充斥着看起来很棒的想法（实际上，技术通常优于现有替代品），但它们最终却淘汰了。现有技术的能力不容小觑。在过去十年中，硅晶太阳能的价格下降显著，特别是有中国巨额投资的情况下。

Nevertheless, as Sam Stranks, who leads an optical-electronics research group at the University of Cambridge, observes, the demand for renewable power is such that a huge ramp-up in production will be needed. He believes perovskites have every chance of sharing in this, both because they are cheap and because he thinks that one more turn of the technological ratchet will improve their efficiency in a way that silicon cannot match.

然而，剑桥大学光学电子研究小组负责人Sam Stranks发现，对可再生能源的需求将会产生大量的增产需求。他认为钙钛矿完全有机会分得一杯羹，一是因为成本便宜，二是技术齿轮的转动将提升它的能源效率，而这是硅无法匹敌的。

Because many chemical combinations result in a perovskite crystal structure, and each of them has different optical properties, choosing the chemistry of a cell also means choosing what part of the spectrum it absorbs, as Oxford Photovoltaics is doing already with its tandem silicon-perovskite cells. Dr Stranks thinks that in time silicon could be cut out of the loop by making tandem cells entirely out of layers of perovskites. This, he reckons, could push efficiency levels up to around 36%. And if that happens, it really might drive silicon solar cells into the shadows.

由于有许多化学组合能最终得到钙钛矿晶体结构，而每一种组织都是会有不同的光学特性，因此，电池化学特性的选择也意味着选择吸收光谱里哪一部分。这也就是牛津光伏在研发串联硅—钙钛矿电池所做的事。Stranks博士认为，很快就能用完全由多层脱离钙钛矿制造的串联电池在发电环节中将硅彻底替代。他认为，这可以将能效水平提高到36％左右。如果能实现的话，确实可能会对硅太阳能电池产生不利影响。