A fair comparison between ultrathin crystalline-silicon solar cells with either periodic or correlated disorder inverted pyramid textures

Abstract

Fabrication of competitive solar cells based on nano-textured ultrathin silicon technology is challenging nowadays. Attention is paid to the optimization of this type of texture, with a lot of simulation and experimental results published in the last few years. While previous studies discussed mainly the local features of the surface texture, we highlight here the importance of their filling fraction. In this work, we focus on a fair comparison between a technologically realizable correlated disorder pattern of inverted nano-pyramids on an ultrathin crystalline-silicon layer, and its periodically patterned counterpart. A fair comparison is made possible by defining an equivalent periodic structure for each hole filling fraction. Moreover, in order to be as realistic as possible, we consider patterns that could be fabricated by standard patterning techniques: hole-mask colloidal lithography, nanoimprint lithography and wet chemical etching. Based on numerical simulations, we show that inverted nano-pyramid patterns with correlated disorder provide typically greater efficiency than their periodic counterparts. However, the hole filling fraction of the etched pattern plays a crucial role and may limit the benefits of the correlated disorder due to experimental restrictions on pattern fabrication.

Performance analysis of rigorous coupled-wave analysis and its integration in a coupled modeling approach for optical simulation of complete heterojunction silicon solar cells

“…The models that enable simulations of thick incoherent and thin coherent layers, including textures of nano-, micro- and several micro-(macro) meter size, are required. Different modeling techniques have been used in simulations of solar cells [11–14], and among them, rigorous coupled-wave analysis (RCWA) has been employed for the optical simulation of thin film or wafer-based solar cells with various textures [2–3 15–17]. However, its applicability, limitations and accuracy in simulation of structures with textures of different types and sizes used in silicon solar cells have not been investigated systematically.…”

“…RCWA, also called the Fourier modal method (FMM), has been widely used in simulations of photovoltaic devices [2–3 15–17], including the structures similar to the ones explored in this paper [3]. It assumes lateral periodicity of the simulated structure.…”

“…This results in a staircase approximation of . While lateral periodicity of the simulated structure is assumed in RCWA, random textures can be simulated by including a sufficient segment of the structure to form a pseudo-periodic simulation domain, where the statistical parameters of the random roughness are still well represented [3]. Spatial 2D discrete Fourier transform of staircase distributions is applied to all ( N ) sublayers, obtaining a discrete power spectrum of distribution for each sublayer.…”

“…In simulations, a random texture from an AFM scan was mirrored across the x and y axis, resulting in an 80 × 80 μm 2 so-called pseudo-periodic texture used in simulations. A similar approach was also taken in [3]. The micropyramid faces are also defined by the slow-etching 111 crystallographic plane, leading to the same 54.7° angle.…”

Biomimetic spiral grating for stable and highly efficient absorption in crystalline silicon thin-film solar cells

“…An obvious dilemma is that the thin film tends to have weak light-absorption efficiency if the film thickness is lower than the absorption length of the material. To overcome this issue, researchers have employed various light-trapping structures to enhance the absorption such as nano-periodic [3][4][5][6][7][8], random [9][10][11] and quasi-random [12][13][14][15][16] surface structures, including plasmonic nanoparticles structures [17][18][19]. Recently, inspired by bionics, biomimetic artificial trapping nanostructures like moth-eye grating and the genetic algorithm-optimized structure are proposed [20,21].…”