Rasmus Schmidt Davidsen

Low surface damage dry etched black silicon

Black silicon (bSi) is promising for integration into silicon solar cell fabrication flow due to its excellent light trapping and low reflectance, and a continuously improving passivation. However, intensive ion bombardment during the reactive ion etching used to fabricate bSi induces surface damage that causes significant recombination. Here, we present a process optimization strategy for bSi, where surface damage is reduced and surface passivation is improved while excellent light trapping and low reflectance are maintained. We demonstrate that reduction of the capacitively coupled plasma power, during reactive ion etching at non-cryogenic temperature (−20 °C), preserves the reflectivity below 1% and improves the effective minority carrier lifetime due to reduced ion energy. We investigate the effect of the etching process on the surface morphology, light trapping, reflectance, transmittance, and effective lifetime of bSi. Additional surface passivation using atomic layer deposition of Al2O3 significant...

Inkjet patterned ALD aluminium oxide for rear PERC metal contacts

A method of patterning atomic layer deposition (ALD) deposited aluminium oxide dielectrics (Al2O3) using an inkjet printer is outlined. This method has applications in creating PERC cell type rear contacts. It is simpler, and uses fewer chemicals than immersive etching techniques such as those involved in photolithography, and the patterning does not cause damage to the silicon evident in laser ablation techniques. Holes with varying diameter between 61-159 μm were etched onto a 50 nm thick ALD Al2O3 passivating dielectric at numerous print settings. The relationship between the printing parameters and the feature size of the holes is discussed.

Simulation and Measurement of Angle Resolved Reflectance from Black Si Surfaces

In this work angle-resolved reflectance from nanostructured Si surfaces realized by maskless RIE texturing has been simulated and measured. The simulation and experimental measurement data show the same trend. Experimentally a total reflectance below 1% for incident angles below 30 and specular reflectance below 0.1% at incident angles below 70 is seen. In both simulation and experiment the specular reflectance is below 10% at incident angles below 65 and below 1% at incident angles below 45 in the case of non-linear graded refractive index. From the simulation results the non-linear graded refractive index yields lower reflectance than the linearly graded refractive index.

Black Silicon Solar Cells

This project aims to optimize the solar cell by applying a new kind of material, black silicon, in order to optimize the absorption of the solar radiation. By changing the surface of the conventional solar cell absorption-material, silicon, on nanoscale, the absorption can possibly and hopefully be improved. If this is the case the next challenge in this project is to incorporate the material in a functioning solar cell, which can actually transform sunlight into electrical power.