Prajapati A, Shalev G
School of Electrical & Computer Engineering, Ben-Gurion University of the Negev POB 653 Beer-Sheva 8410501 Israel
The Ilse-Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev POB 653 Beer-Sheva 8410501 Israel.
Nanoscale Adv. 2019 Oct 15;1(12):4755-4763. doi: 10.1039/c9na00599d. eCollection 2019 Dec 3.
Texturing the front surface of thin film photovoltaic cells with ordered or disordered arrangements of subwavelength structures is beneficial in terms of efficient light harvesting as well as efficient carrier extraction. Previous studies demonstrated efficient broadband absorption of solar radiation with surface arrays of subwavelength inverted cones (light funnels - LFs). In the current work, we use three-dimensional finite-difference time-domain electromagnetic calculations as well as three-dimensional device calculations to examine carrier extraction from photovoltaic cells that are composed of LF arrays on top of underlying substrates. For the selected geometry under examination, we show a broadband absorption enhancement of 14% for the LF photovoltaic cell compared with a cell based on the respective optically optimized nanopillar arrays. However, we show that the nominal power conversion efficiency is 60% higher in the LF cell which is due to the enhancement of both open-circuit voltage and short-circuit current. The higher open-circuit voltage in the LF cell is due to the higher injection of photocarriers, and the higher short-circuit current is a result of the unique LF geometry that supports efficient carrier extraction due to the naturally occurring gradients of the quasi-Fermi levels and minority carrier conductivity that allow for enhanced contact selectivity. We believe that this work paves the way towards a new approach for carrier collection in photonic devices for energy applications.
用亚波长结构的有序或无序排列对薄膜光伏电池的前表面进行纹理化处理，在高效光捕获以及高效载流子提取方面是有益的。先前的研究表明，具有亚波长倒锥（光漏斗-LF）表面阵列的太阳能辐射具有高效的宽带吸收。在当前工作中，我们使用三维时域有限差分电磁计算以及三维器件计算，来研究由位于底层衬底顶部的LF阵列组成的光伏电池中的载流子提取。对于所研究的选定几何结构，我们表明，与基于各自光学优化的纳米柱阵列的电池相比，LF光伏电池的宽带吸收增强了14%。然而，我们表明，LF电池的标称功率转换效率高出60%，这是由于开路电压和短路电流均有所增强。LF电池中较高的开路电压是由于光生载流子的注入增加，而较高的短路电流是独特的LF几何结构的结果，由于准费米能级和少数载流子电导率的自然梯度支持高效载流子提取，从而实现了增强的接触选择性。我们相信，这项工作为能量应用的光子器件中的载流子收集开辟了一条新途径。
