Eyderman Sergey, John Sajeev
Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 1A7, Canada.
Sci Rep. 2016 Jun 23;6:28303. doi: 10.1038/srep28303.
We demonstrate nearly 30% power conversion efficiency in ultra-thin (~200 nm) gallium arsenide photonic crystal solar cells by numerical solution of the coupled electromagnetic Maxwell and semiconductor drift-diffusion equations. Our architecture enables wave-interference-induced solar light trapping in the wavelength range from 300-865 nm, leading to absorption of almost 90% of incoming sunlight. Our optimized design for 200 nm equivalent bulk thickness of GaAs, is a square-lattice, slanted conical-pore photonic crystal (lattice constant 550 nm, pore diameter 600 nm, and pore depth 290 nm), passivated with AlGaAs, deposited on a silver back-reflector, with ITO upper contact and encapsulated with SiO2. Our model includes both radiative and non-radiative recombination of photo-generated charge carriers. When all light from radiative recombination is assumed to escape the structure, a maximum achievable photocurrent density (MAPD) of 27.6 mA/cm(2) is obtained from normally incident AM 1.5 sunlight. For a surface non-radiative recombination velocity of 10(3) cm/s, this corresponds to a solar power conversion efficiency of 28.3%. When all light from radiative recombination is trapped and reabsorbed (complete photon recycling) the power conversion efficiency increases to 29%. If the surface recombination velocity is reduced to 10 cm/sec, photon recycling is much more effective and the power conversion efficiency reaches 30.6%.
通过对耦合的电磁麦克斯韦方程和半导体漂移扩散方程进行数值求解，我们在超薄（约200纳米）砷化镓光子晶体太阳能电池中实现了近30%的功率转换效率。我们的结构能够在300 - 865纳米波长范围内实现波干涉诱导的太阳光捕获，从而吸收近90%的入射太阳光。我们针对等效体厚度为200纳米的砷化镓进行的优化设计是一种方形晶格、倾斜锥形孔的光子晶体（晶格常数550纳米，孔径600纳米，孔深290纳米），用AlGaAs钝化，沉积在银背反射器上，顶部接触为ITO，并封装有SiO2。我们的模型包括光生电荷载流子的辐射复合和非辐射复合。当假设来自辐射复合的所有光都逸出结构时，从垂直入射的AM 1.5太阳光中可获得的最大光电流密度（MAPD）为27.6 mA/cm²。对于表面非辐射复合速度为10³ cm/s的情况，这对应于28.3%的太阳能功率转换效率。当来自辐射复合的所有光都被捕获并重新吸收（完全光子回收）时，功率转换效率提高到29%。如果表面复合速度降低到10 cm/sec，光子回收会更有效，功率转换效率达到30.6%。
