Optimization of the optical properties of nanostructured silicon surfaces for solar cell applications

Abstract

Surface nanostructuration is an important challenge for the optimization of light trapping in solar cell. We present simulations on both the optical properties and the efficiency of micro pillars-MPs-or nanocones-NCs-silicon based solar cells together with measurements on their associated optical absorption. We address the simulation using the Finite Difference Time Domain method, well-adapted to deal with a periodic set of nanostructures. We study the effect of the period, the bottom diameter, the top diameter, and the height of the MPs or NCs on the efficiency, assuming that one absorbed photon induces one exciton. This allows us to give a kind of abacus involving all the geometrical parameters of the nanostructured surface with regard to the efficiency of the associated solar cell. We also show that for a given ratio of the diameter over the period, the best efficiency is obtained for small diameters. For small lengths, MPs are extended to NCs by changing the angle between the bottom surface and the vertical face of the MPs. The best efficiency is obtained for an angle of the order of 70 . Finally, nanostructures have been processed and allow comparing experimental results with simulations. In every case, a good agreement is found. V

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

“…For example, nano-texturing of the front-side and/or back-side surfaces of the solar cell allows to enhance the coupling of the incident light into the active layer via light trapping [7,8]. Attention is paid to the optimization of this type of texture and a lot of simulations and experimental results on nanostructured solar cells have been published in the last few years [9][10][11][12][13]. In spite of all these efforts, an important question has not yet found a definite answer: Is the best type of corrugation periodic, quasi-periodic or random?…”

Fabrication and characterization of Al2O3 /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

“…Recently, absorption improvement in c-Si thin film solar cells by means of photonic management (PM) engineering, such as photonic crystals, 4,5 nano-wires (nano-rods), 6,7 nanopores (nanoholes), 8,9 nanocones (nanodomes), [10][11][12][13][14][15] and inverted nano-pyramids 16 has been theoretically studied. However, all these light-trapping structures inevitably lead to significant increase in the device surface area and introduce surface defects, resulting in elevated carrier loss.…”

Effects of Pillar Height and Junction Depth on the Performance of Radially Doped Silicon Pillar Arrays for Solar Energy Applications

“…[ 17 ] Previous publications, which focus on pillars with diameters of up to a few µm, have shown a positive effect of increased pillar heights on the effi ciency of solar cells. [ 10,18,19 ] Voigt et al have used simulations to predict the most effi cient pillar radius (in the range 62-4000 nm) and height (range 3-384 µm) [ 18 ] and found an optimum value of 2 µm for the pillar diameter with a corresponding height of 96 µm. Another important aspect in the design of the pillar array is the diameter-over-pitch (D/P) ratio.…”

“…Previous studies in the fi eld of photovoltaics have shown large improvement in solar cell performance, such the highest theoretical and experimental effi ciencies for various systems. [19][20][21] The radial junction depth variation in micropillars can be varied by tuning the doping process, and a trend of improved JV characteristics for thinner junctions, down to 50 nm, has been shown in simulations. [ 20 ] A thin junction leads to less recombination, which implies that the outer highly doped shell of a radially doped micropillar should be kept thin, but also should keep its carrier separation functionality.…”