Inkjet-printed Ultrathin Solar Cells
The rainbow-colored soap bubbles under the sun always paint a dreamy, unrealistic, and airy-fairy picture. Yet, the scientists from King Abdullah University of Science and Technology (KAUST), Saudi Arabia, have used these fragile surfaces to demonstrate their groundbreaking innovation. They have invented an ultrathin solar cell that is so light that it can sit on the soap bubble surface. Yes, for real.
Indium is a toxic and expensive metal, which is a necessary element to produce thin-film solar cells. Thin-film solar cells, or what we call the CIGS (copper indium gallium selenide) solar cells, are the third generation of photovoltaic cells. They have been proven to have high power generation efficiency of up to 20.3% with just a tiny cell. When the cells are put together as a module, the efficiency can still reach 14%. Yet, because of the high costs of the rare materials and complex production processes, scientists have been working hard to find alternatives to make highly-efficient-low-budget thin-film solar cells.
The researchers from KAUST made a breakthrough. They have developed a transparent conductive polymer called PEDOT: PSS. A layer of organic photovoltaic material is in the middle of the polymer. The solar cells can work indium-free and be inkjet-printed, while the structure is thin and light enough to be carried on soap bubble surfaces.
Inkjet printing is a science on its own. The scientists need to formulate functional inks for each layer of the solar cell architectures. They also need to overcome the intermolecular force within the cartridge and the ink to let the tiny nozzle eject the very fine ink droplets one by one before they go for the drying stage and other processes to finish the entire production.
These inkjet-printed ultrathin solar cells are coated with waterproof parylene, which can prevent damage from the weather. In the glass plate tests, the researchers found that the inkjet-printed solar cells’ light-electric power conversion efficiency is 4.73%, which is not high. However, the researchers believe that this new technology has its competitive advantages: with the support from computers, inkjet printing can diversify the design of solar cells because the inks can be printed on specific places. So, the ultrathin solar cells can flexibly be made or applied to various devices, skipping the molding process, which saves materials and costs.
The size of batteries is very important to some devices, such as miniaturized sensors, wearable electronics, electronic skins, sensors for flying devices, and biosensors. The toxic-free inkjet-printed solar cell, with its ultrathin and superlight structure, is the perfect power solution for the mentioned devices. Let’s hope scientists can further advance this technology, especially its power generation efficiency, to broaden its application.
(To read the article at SolarCare Programme’s website HERE)
可貼在肥皂泡上的超薄太陽能電池
在陽光底下泛出七彩炫光的肥皂泡，總會給人一種夢幻、虛浮、不切實際的感覺。但一班來自沙地阿拉伯阿卜杜拉國王科技大學（KAUST）的科學家，卻利用這些浮幻的肥皂泡，向我們確實地展示了他們的研究成果。他們研發了一種超薄的太陽能電池，材質又薄又輕，使其能黏附在肥皂泡的表面上，可謂給太陽能科技帶來了革新。
銦(Indium)是貴金屬，而且有毒，但在現有的薄膜太陽能技術中，卻是不能缺少的元素。銅銦鎵硒型（CIGS）是第三代太陽能電池的代名詞，效能極高，一塊細小面積的電池，光轉電效率已經達到20.3%，而模組的效率也達14%。可是，因原料稀有，再加上複雜的製作過程，這種電池的生產成本非常高。因此科學家們都在積極研發效率高、成本低的薄膜太陽能電池。
KAUST的研究團隊在這一範疇中得到了革命性的突破。他們研發出一種極為透明的導電聚合物PEDOT：PSS，這種聚合物中間夾了一層有機太陽能材料，不含任何銦元素，只需利用噴塗印刷（inkjet printing），就能製造出薄得能黏在肥皂泡表面上的超薄太陽能電池。
噴塗印刷並不是一門簡單的學問。要運用這技術製造超薄膜太陽能電池，科學家須特意為太陽能電池調配出具特殊功能的油墨（functional inks），更要克服墨盒和墨水之間的分子間作用力（intermolecular force），方能從極小的噴嘴中噴射出一滴滴油墨，然後才處理乾燥墨膜、成品等工序。
這種「噴塗式超薄膜太陽能電池」（inkjet-printed ultrathin solar cell）的外層塗有防水的聚對二甲苯（parylene），可避免太陽能電池因風雨而導致的耗損。在玻璃基板實際測試後，研究團隊發現其光轉電效率為 4.73%。雖然效率不高，但研究團隊認為，這種技術另有優勢：噴墨印刷透過電腦輔助，不但使太陽能板的設計更多樣化，更能將墨水準確地噴印於特定位置上，不用模具，就能製作出各式各樣的特殊元件，既節省原料、又能降低成本。
再者，噴塗式超薄膜太陽能電池不含有毒貴金屬銦，加上它極輕極薄，適合應用在發展受限於電池大小的設備上，例如小型感測器、穿戴式電子設備、電子皮膚、飛行器感測器、生物感測器等。希望在不久的將來，科學家能進一步提高噴塗式超薄膜太陽能電池的發電效率，進而擴大它的應用範圍。