Perovskite crystals may represent the future of solar power

Their efficiency rates far exceed those of conventional silicon panels
它们的效率远远超过传统硅板

2024年10月24日 05:34 上午 |牛津大学

IT IS COMMONLY claimed, and also true, that enough sunlight falls on Earth in the course of an hour to meet a year’s worth of global power needs. Some of that sunlight is currently converted into electricity by arrays of solar panels: by the end of 2023, these panels covered almost 10,000 square kilometres of Earth’s surface, producing some 1,600 terawatt-hours of electricity, about 6% of that generated worldwide.

人们普遍认为，一小时内照射到地球上的阳光足以满足全球一年的电力需求，这也是事实。目前，部分阳光通过太阳能电池板阵列转化为电能：到 2023 年底，这些电池板覆盖了近 10,000 平方公里的地球表面，产生约 1,600 太瓦时的电力，约占全球发电量的 6%。

The amount of installed solar-capacity has been doubling roughly every three years. This is happening as the silicon-based solar cells used in the panels have been getting cheaper with intense competition among firms in China, which with state support have come to dominate the industry. At the same time, researchers have found ways to make the cells better at absorbing the energy in sunlight. Modern solar panels operate with efficiency rates of 22-24%—a massive increase from the 6% achieved when the first practical solar cells were invented in the 1950s at Bell Labs in New Jersey, and were so expensive they mostly powered satellites.

太阳能装机容量大约每三年翻一番。发生这种情况的原因是，由于中国企业之间的激烈竞争，电池板中使用的硅基太阳能电池变得越来越便宜，而在国家的支持下，中国企业已在该行业占据主导地位。与此同时，研究人员找到了使细胞更好地吸收阳光能量的方法。现代太阳能电池板的运行效率为 22-24%，与 20 世纪 50 年代新泽西州贝尔实验室发明第一批实用太阳能电池时的 6% 相比，这是一个巨大的提高，而且价格昂贵，主要为卫星提供动力。

Yet most processes have their limits. The maximum theoretical efficiency of a silicon solar cell—the amount of energy in sunlight that is turned into electricity—is around 29%. This is possible only in laboratory conditions. When cells are packed together into solar panels, the total efficiency of the panel is unlikely to get above 26%. This is partly because the spaces between cells and other parts of the panel, such as the frame, do not contribute to making electricity. There are also inevitable losses of energy in the wires connecting the cells.

然而大多数流程都有其局限性。硅太阳能电池的最大理论效率（将阳光中的能量转化为电能）约为 29%。这只有在实验室条件下才有可能。当电池组装成太阳能电池板时，电池板的总效率不太可能超过 26%。部分原因是电池和电池板其他部分（例如框架）之间的空间无助于发电。连接电池的电线中也不可避免地存在能量损失。

The future of solar power, however, could lie in a new, more efficient, type of solar cell that has just gone into production. Made with a family of crystalline materials called perovskites, they are capable of delivering panels with practical efficiency rates well above 30%.

然而，太阳能的未来可能在于一种刚刚投入生产的新型、更高效的太阳能电池。它们由一系列称为钙钛矿的晶体材料制成，能够提供实际效率远高于 30% 的面板。

Jumping the gap

跳跃差距

Traditional solar cells typically contain two layers of ultra-pure silicon, both doped with an additive to make them semiconducting (ie, the ability to work as either a conductor or insulator). As they absorb light, electrons receive enough energy to jump across the junction between the layers, producing an electric current. Although other semiconductors can do the same, none rivals the affordability of silicon, which is produced cheaply from sand.

传统的太阳能电池通常包含两层超纯硅，两层都掺杂了添加剂，使其成为半导体（即能够作为导体或绝缘体工作）。当它们吸收光时，电子会接收到足够的能量来跨越各层之间的连接处，从而产生电流。尽管其他半导体也能做到同样的事情，但没有一种半导体的价格可以与硅相比，因为硅是用沙子廉价生产的。

The original perovskite is a mineral called calcium titanium oxide. It was discovered in 1839 and named after Count Lev Perovski, a Russian mineralogist. The name has since become a generic term for substances with a similar crystalline structure. One of the things that makes perovskites so attractive to researchers as an alternative to silicon is that, in addition to being efficient at absorbing the energy in sunlight, they can also be made cheaply from easily obtainable materials, including a number of metals and halogens, like chlorine, bromine and iodine.

最初的钙钛矿是一种叫做钙钛矿氧化物的矿物。它于 1839 年被发现，并以俄罗斯矿物学家列夫·佩罗夫斯基伯爵 (Count Lev Perovski) 的名字命名。该名称从此成为具有相似晶体结构的物质的通用术语。钙钛矿作为硅的替代品对研究人员如此有吸引力的原因之一是，除了能够有效吸收阳光中的能量之外，它们还可以由容易获得的材料（包括许多金属和卤素）廉价地制成，如氯、溴和碘。

Even though their light-absorbing superpowers have been known for some time, they have been difficult to harness, not least because perovskites degrade quickly and can be susceptible to moisture. Researchers are therefore searching for ways to make them more stable and to adapt manufacturing processes to protect the cells from the elements.

尽管它们的吸光超能力早已为人所知，但它们却很难利用，尤其是因为钙钛矿降解速度很快，而且容易受潮。因此，研究人员正在寻找使它们更加稳定并调整制造工艺以保护电池免受自然因素影响的方法。

A leader in developing perovskite panels is Oxford PV, a British company. The firm has developed “tandem cells”, consisting of a thin layer of perovskite placed on a bed of silicon. The idea is that the two materials working together can extract a greater amount of energy from sunlight than each could individually. To do so, the perovskite layer is tweaked to absorb light from the blue end of the spectrum while the silicon layer mops up the wavelengths at the red end, says Chris Case, the company’s chief technology officer.

开发钙钛矿面板的领导者是英国公司 Oxford PV。该公司开发了“串联电池”，由放置在硅床上的一层薄薄的钙钛矿组成。这个想法是，两种材料一起工作可以从阳光中提取比每种材料单独提取更多的能量。该公司首席技术官克里斯·凯斯(Chris Case)表示，为此，对钙钛矿层进行了调整，以吸收光谱蓝端的光，而硅层则吸收了红端的波长。

The firm has opened a factory in Germany which has just started to supply commercial tandem-cell solar panels to its first customer, an unnamed utility in America. The panels are being installed, along with conventional silicon units, at a new grid-connected solar farm. This will provide perovskites with their first big test at this scale, not just for efficiency but also durability and longevity. As silicon panels are expected to continue working for 20-25 years, perovskites must demonstrate similar lifespans.

该公司在德国开设了一家工厂，刚刚开始向其第一个客户（美国一家不知名的公用事业公司）供应商用串联电池太阳能电池板。这些电池板与传统的硅装置一起安装在一个新的并网太阳能发电场。这将为钙钛矿提供首次如此规模的大测试，不仅是效率，还有耐用性和寿命。由于硅面板预计可以持续工作 20-25 年，因此钙钛矿必须具有类似的使用寿命。

The first production panels have an average efficiency of 24.5%, adds Dr Case. A new generation under development has reached 26.9%, and this is expected to increase to well over 30% as research continues. The theoretical efficiency limit for a perovskite tandem cell in a laboratory is around 43% (compared with the 29% for silicon) even if that is also unlikely to be reached once it is integrated into a panel.

Case 博士补充道，第一批生产的电池板的平均效率为 24.5%。正在开发的新一代已达到 26.9%，随着研究的继续，这一数字预计将增加到 30% 以上。实验室中钙钛矿串联电池的理论效率极限约为 43%（相比之下，硅为 29%），即使一旦集成到面板中也不太可能达到这一目标。

Other companies are also close to commercialising their versions of perovskite-on-silicon solar panels. Hanwha, a big South Korean industrial group, has invested 137bn won ($102m) in a factory to make tandem cells for its QCells range of solar panels. At lab scale, the firm says individual cells have achieved a maximum efficiency of 29.3%.

其他公司也即将将其钙钛矿硅太阳能电池板商业化。韩国大型工业集团韩华 (Hanwha) 已投资 1,370 亿韩元（1.02 亿美元）建厂，为其 QCells 系列太阳能电池板生产串联电池。该公司表示，在实验室规模上，单个电池的最高效率达到了 29.3%。

The current world record for a lab-based perovskite tandem cell is 34.6%. This was claimed in June by LONGi Green Energy Technology, a big Chinese manufacturer. It began working on mass-production for the cells in October 2023. The firm says it has also achieved 30.1% efficiency in a prototype commercial-size panel, though it has not yet announced when production will begin. ■

目前实验室钙钛矿串联电池的世界纪录是 34.6%。中国大型制造商隆基绿能科技于 6 月份宣称了这一点。该公司于 2023 年 10 月开始致力于电池的大规模生产。该公司表示，其商业尺寸面板原型也实现了 30.1% 的效率，但尚未宣布何时开始生产。 ■