前后光栅周期对于双光栅结构薄膜太阳能电池光俘获效应的影响

本文用时域有限差分法对硅层等效厚度为100 nm的具有不同前后光栅周期的介质/金属双光栅结构薄膜太阳能电池进行了模拟分析,比较了三角形最佳相同与不同周期光栅结构的吸收光谱特性,分析了光栅高度、填充比、硅吸收层厚度对最佳相同和不同周期光栅结构光吸收特性的影响,以及相应结构中导致光吸收增强的共振模式.结果表明前后光栅周期为1:1的共形双光栅结构中存在光泄漏现象,偏离1:1后的光栅结构可有效地抑制低级次衍射光的泄漏,前光栅周期小于后光栅周期的结构光吸收性能的提高来自于平面波导模式在吸收层中的有效激发和传播,而前光栅周期大于后光栅周期的结构光吸收性能的提高则来自于后光栅界面上所激发的等离子体极化模式.在较厚的硅吸收层厚度,前后光栅周期比为1:2和1:3的电池结构也会出现光泄漏现象,从而使具有最大光吸收效率的结构偏离这些周期比结构的位置.     

复合绒面ZnO:Al光栅增强薄膜硅电池陷光特性

探讨复合绒面ZnO:Al光栅对薄膜硅太阳能电池光俘获效率的影响.织构了由关联长度(lcor)和平均高度(have)表征的绒面,叠加到周期为980nm和槽深为160nm的一维正弦ZnO:Al光栅上,形成复合绒面ZnO:Al光栅.前电极AZO光栅,当lcor较小和have较大时,电池的短路电流较高.若lcor取0.01,则短路电流随have的增大而升高,由have=0.05时的21.93 mA/cm2增加到have=0.80时的23.80mA/cm2.置于背电极且lcor=0.01时,短路电流随have的增加而逐渐减小,由have=0.05时的25.50mA/cm2降到have=0.80时的24.81 mA/cm2.采用直流溅射和化学腐蚀方法分别制备了无绒面ZnO:Al光栅和lcor=0.01,have=0.14的复合绒面ZnO:Al光栅.反射率测试结果表明,复合绒面ZnO:Al光栅总反射率(8.3%)较无绒面ZnO:Al栅(10.2%)降低了1.9%,镜面反射率(4.7%)较无绒面ZnO:Al栅(6.8%)降低了2.1%.以实验制备的两种光栅为模型用严格耦合波方法进行模拟,计算结果表明与无绒面ZnO:Al光栅相比,复合绒面ZnO:Al光栅的总反射率和镜面反射率均显著下降.复合绒面ZnO:Al光栅由于具有较好的减反作用更适合用作薄膜电池前电极,从而得到更高的短路电流;而无绒面ZnO:Al光栅因具有较高的反射适用于背电极,能将到达背电极的光子重新返回硅吸收层而获得更高的陷光效率.     

Light trapping enhancement in thin film silicon solar cells with different front and back grating periodicities

Dual-grating structure thin-film silicon solar cells with different front and back grating periodicities are designed The geometrical parameters of both gratings are investigated. The reflection is greatly reduced by the front grating, whereas the absorption in the long wavelength is increased because of the back grating. The short circuit current of the combined structure is enhanced by 16.8% for a 1μm thick c-Si layer compared with that of the conformal grating structure. The short circuit current can be further increased by creating a relative lateral displacement between the front and back gratings. The displacement results in a more remarkably enhaneed absorption when the thickness of the aetive layer is reduced, indicating its importance in the design of ultra-thin high-efficiency solar cells.     

亚微米AZO光栅及其漫透射分布特性

探讨亚微米掺铝氧化锌(AZO)光栅的漫透射光谱特性。在AZO薄膜上涂布光刻胶,用325nm激光双光束干涉曝光得到掩模图案。将其置于质量分数为0.5%的稀盐酸溶液中湿法刻蚀,制备出周期(780～1280nm)和高度(60～300nm)能独立调控的AZO一维光栅。正入射双向透射分布函数(BTDF)测试结果表明,400～900nm波段内平均镜面透射率随光栅周期增大而降低,与紫外-可见分光光度计测得的结果吻合;同时,周期越大被衍射到30°～80°范围内的漫透射比重和漫透射峰值均越大,而峰位角越小。根据光栅方程对实验结果给出了合理的解释。     

Light scattering effect of submicro-textured Ag/Al composite films prepared at lower substrate temperatures

We present a new and practical approach for preparing submicro-textured silver and aluminum (Ag/Al) double-structured layers at low substrate temperatures. The surface texturing of silver and aluminum double-structured layers was performed by increasing the deposition temperature of the Al layers to 270℃. The highly submicro-textured silver and aluminum double-structured layers were prepared by thermal evaporation on quartz glasses and their surface microstructure, light scattering properties, and thermal stability were investigated. Results showed that the highly submicro-textured Ag/Al composite films prepared at low substrate temperatures used as back reflectors not only can enhance the light scattering and have good thermal stability, but also have good adhesion properties. In addition, their fabrication is low cost and readily carried out.     

Light trapping enhancement with combined front metal nanoparticles and back diffraction gratings

In this letter, a design with both metal nanoparticles and back diffraction gratings is put forward for enhancing the efficiency of thin film silicon solar cells. The coupling mechanism between the metal nanoparticles and silicon absorber layer, and that between the incident light and the modes of the silicon absorption layer through the grating layer are both analyzed. The interaction between the front metal nanoparticles and back gratings is analyzed, which substantially increases the light trapping by 58% com- pared to fiat solar cell.     

湿法和溶脱法的亚微米ZnO:Al光栅制备

以激光干涉法得到的光刻胶图案为掩模,采用湿法刻蚀和溶脱-剥离法制备了具有良好减反射特性的亚微米掺铝氧化锌（ZnO:Al, AZO）光栅。表面形貌特征和反射光谱测试结果表明,湿法刻蚀较溶脱-剥离法得到的AZO光栅表面更为粗糙,两者均方根粗糙度分别为25.4,7.6 nm。在400～900 nm波段,两种方法制备的周期和高度相同的光栅,平均总反射率分别由AZO薄膜的12.5%下降到8.3%和10.2%。两者的平均镜面反射率分别为6.2%和6.6%,平均漫反射率分别为2.1%和3.6%。湿法刻蚀得到的表面较为粗糙AZO光栅的漫反射明显减弱,从而导致总的减反特性优于溶脱-剥离法得到的表面起伏相对较小的AZO光栅。