SBIR Phase I: Low-Temperature Route to Cu(In,Ga)Se2 for Flexible Photovoltaics

这个小型企业创新研究（SBIR）一期项目提供了一种低温加工复合半导体材料铜铟镓二硒化（CIGS）的新方法。CIGS目前被用作一些薄膜多晶太阳能电池的太阳能吸收层，其效率达到了19%，创下了世界纪录。由于成本效益的考虑，显示器和光伏（PV）行业正朝着连续卷对卷制造的方向发展，而卷对卷CIGS太阳能电池工艺目前的模块效率为6%至8%。这被认为是由于使用聚酰亚胺衬底时需要较低的烧结温度，导致CIGS吸收层中的微结构限制。该项目的研究目标是证明使用低温处理步骤提高CIGS太阳能电池的转换效率。为了做到这一点，小晶粒CIGS薄膜将受到有利于晶粒生长的条件，从而产生大晶粒的多晶半导体。将仔细控制和优化温度，以确定该过程是否可能使经济的底物，如聚对苯二甲酸乙二醇酯。如果成功，该方法将普遍适用于多晶金属硫族化物电子材料，其中可以通过减少晶界数量来改善性能。该项目的商业应用是制造高效率、柔性的太阳能电池半导体材料。该项目允许以CIGS太阳能电池为第一个例子，对半导体生长方法进行可行性论证。假设低温处理导致大颗粒材料的形成，并提高太阳能转换效率，该工艺可以作为现有卷对卷CIGS制造设施的插件使用。在柔性和轻质基板上开发15%效率的CIGS太阳能电池将满足用于便携式电子产品（如手机和笔记本电脑）的高端太阳能电池产品的需求，这些产品10年的市场估计为50亿美元并非不合理。虽然现有的光伏技术可能满足便携式光伏的成本目标（即10美元/瓦），但鉴于低比功率密度和模块的不灵活性，这些技术并不适用，因此为新兴的太阳能电池技术提供了重要的机会。对于这种消费者应用，通过使用便携式光伏增加的价值是无需“插电”为电力系统充电的便利性。除了CIGS太阳能电池外，这种低温生长方法还可以通过晶体管和/或热电器件的新途径影响柔性电子和电子纺织品等新兴领域。

This Small Business Innovation Research (SBIR) Phase I project provides a new approach to low-temperature processing of a compound semiconductor material, copper indium gallium diselenide (CIGS). CIGS is presently being used as the solar absorber layer in some thin film polycrystalline solar cells with world-record efficiencies of 19 percent. While there is a move in the display and photovoltaic (PV) communities towards continuous roll-to-roll manufacturing owing to cost benefits, roll-to-roll CIGS solar cell processes currently give 6 to 8 percent efficient modules. This is thought to be due to microstructural limitations in the CIGS absorber layer as a consequence of lower temperature sintering required when using a polyimide substrate. The research objective of this project is to demonstrate improved conversion efficiencies for CIGS solar cells using a low-temperature processing step. To do this, small grain CIGS films will be subjected to conditions that favor grain growth yielding a large-grained polycrystalline semiconductor. Temperature will be carefully controlled and optimized to determine if this process might enable economical substrates such as polyethylene terephthalate. If successful, the approach would be generally applicable to polycrystalline metal chalcogenide electronic materials where performance improvements might be anticipated with a reduction in the number of grain boundaries. The commercial application of this project is in the manufacture of high efficiency, flexible, solar cell semiconductor material. This project allows a feasibility demonstration for a semiconductor growth methodology using CIGS solar cells as the first example. Assuming the low-temperature treatment results in the formation of large-grained materials and gives increased solar conversion efficiencies, the process could be utilized as a plug-in at an existing roll-to-roll CIGS manufacturing facility. The development of 15 percent efficient CIGS solar cells on flexible and lightweight substrates would address the needs of higher-end solar cell products used in portable electronics such as cell phones and laptops where a 10-year market estimate of $5 billion is not unreasonable. While existing PV technologies may meet the cost target for portable PV (i.e. $10/W) these are not applicable given the low-specific power density and inflexibility of the modules thus providing a significant opportunity for an emerging solar cell technology. For this consumer application, the value added through the use of portable PV is the convenience of never "plugging in" to recharge a power system. In addition to CIGS solar cells, this low-temperature growth approach could impact the emerging fields of flexible electronics and electronic textiles through new routes to transistors and/or thermo-electrics.