摘要
典型的商业化太阳能电池组件封装结构由光伏玻璃、胶膜、电池片、背膜等部分组成,由于光伏封装玻璃与空气之间存在界面,会带来约4%的太阳光反射,这部分太阳光无法参与到光电转换过程中,造成了一定的光损耗。减反射膜可以有效地抑制由于界面存在折射率差而导致的光反射损耗,因此,在光伏组件中普遍需要在光伏玻璃表面镀减反射膜,这具有重要的现实意义和巨大的经济价值。然而,由于太阳光的宽谱特性,光伏组件面临着严苛的户外环境使用要求,这需要光伏玻璃减反射膜不仅具有较好的减反增透特性,还需在复杂环境下保持稳定,并且符合光伏产业大面积、低成本、均匀成膜的技术要求。事实上,实现兼具以上特性的减反射膜材料制备和镀膜是极具挑战的。与玻璃衬底折射率匹配的减反射膜需要具有极低的折射率(低于自然界中天然材料的折射率),为了获得这种超低折射率需要在材料中引入一定比例的孔隙结构,而这与所要求的严苛环境下材料的稳定性存在矛盾。因此,光伏玻璃减反射膜研究除追求优异的光学特性外,维持其在复杂气候条件下的稳定性也至关重要,减反射膜耐候性、机械强度以及多功能特性(如自清洁、防尘抗污和防潮等)增强方面的探索都成为主要研究课题。在光学特性方面,利用仿生折射率渐变结构提升减反射膜的宽光谱、广角减反特性研究已取得了一系列进展。而在光伏产业中,基于光学特性、稳定性和制造成本的考虑普遍采用溶胶-凝胶二氧化硅单层减反体系,相比于传统的纳米实心二氧化硅颗粒制备的多孔二氧化硅减反射膜,新型介孔二氧化硅和具有封闭孔隙结构的空心二氧化硅减反射膜体现出更好的耐候性和机械强度,同时维持了所需的孔隙率,保持了较好的减反增透特性。此外,为了应对在不同气候环境下的长期应用需求,研究者们进行了一些二氧化硅减反射膜自清洁和防尘抗污等多功能改性方面的探索,但目前在实现同时具有优异的光学特性、较高的力学性能和长效的耐候性的多功能减反射膜方面仍存在较大挑战。本文归纳了光伏玻璃减反射膜的研究进展,从减反射膜的基本概念、原理出发,介绍了针对光伏玻璃减反射膜的特定评价方法,并围绕当前光伏产业中普遍采用的溶胶-凝胶二氧化硅单层减反射膜制备技术进一步对具有三类不同孔隙结构的二氧化硅减反射膜体系进行了介绍,分析了光伏玻璃减反射膜所面临的问题并对其发展趋势进行了展望,以期为制备减反增透特性更优异、在极端环境下更稳定和具有更丰富表面功能特性的新型光伏玻璃减反射膜提供参考。
T ypical commercial PV modules are composed of PV glass, EVA, solar cells, back reflectors, and so forth. Due to the interfacial reflection between PV glass and air, a portion of sunlight, around 4%, is reflected, which cannot take part in the optoelectronic conversion, resulting in a certain of light loss. Antireflection coatings (ARCs) can effectively suppress the loss caused by the interfacial reflection. To some extent, it is necessary to fabricate ARCs on the surface of PV glass in PV modules, which is of great significance for practice and economy. However, ARCs have to possess an improved transmittance and a good stability under harsh environments since the solar irradiance covers a broad spectral range and PV modules are applied outdoors. On the other hand, it is necessary that ARCs should be prepared in large-area and low-cost due to the demand from PV industry. In fact, fulfilling the aforementioned requests simultaneously is highly challenging. The refractive index of ARCs on PV glass should be low for impedance matching, which is lower than that of materials in nature. For achieving the low refractive index, a certain of porosity is introduced, but it conflicts with the demanding stability. It implied that the stability of ARCs under harsh environments is of great importance besides excellent optical properties. The studies on improvements in durability, mechanical strength, and multi-functiona- lities of ARCs, such as self-cleaning, anti-dust and humidity-resistant properties, have attracted much attention. Concerning the optical properties, the bio-inspiredgraded-refractive-index ARCs exhibited broadband and omnidirectional antireflection. In the PV industry, the sol-gel silica single-layered ARCs are usually applied considering optical properties, stability, and manufacturing cost. Compared with conventional porous silica ARCs, consisting of solid silica nanoparticles, novel mesoporous and hollow silica ARCs with meso-sized and closed pores respectively, posses better durability and mechanical strength while preserving good antireflection. Besides, for long-term application under various environments, many efforts have been made on multi-functional self-cleaning, anti-dust, and anti-soiling ARCs via chemical modification, though the simultaneous realization of excellent optical, mechanical, and long-term durability is highly challenging so far. This review offers a retrospection of the research efforts with respect to ARCs on PV glass, and provides an introduction on the concepts, fundamentals, and evaluation methods of ARCs in PV modules. We concentrate on the preparation of sol-gel silica single-layered ARCs that are usually applied in PV industry and provide the detailed descriptions on three kinds of silica ARCs with different pore structures. We point out the challenges that state-of-the-art ARCs face and provide a perspective for achieving novel ARCs with better antireflection, stability, and versatile surface functionalities.
作者
林昇华
张景
艾玲
鲁越晖
王林军
宋伟杰
LIN Shenghua;ZHANG Jing;AI Ling;LU Yuehui;WANG Linjun;SONG Weijie(School of Materials Science and Engineering, Shanghai University, Shanghai 200444;Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201;Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou 213164)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2019年第21期3588-3595,共8页
Materials Reports
基金
国家自然科学基金(61574144
61605224)
浙江省自然科学基金(LY17A040004)
宁波市自然科学基金(2017A610021)~~
关键词
减反射膜
光伏玻璃
溶胶-凝胶
改性
antireflection coatings
photovoltaic glass
sol-gel
modification
