Black Silicon Structures
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Nanostructuring on the surface of silicon can make high efficient solar cells possible by lowering the reflection. Silicon wafers were successfully wet chemically etched with metal-assistance, to create a black silicon structure (BSiS). Different passivation layers and methods, PECVD and chemical, were tested with the purpose of decrease surface recombination. Silicon oxide was applied with PECVD with four different deposition times; 15, 30, 45 and 60 seconds. All the samples had promising surface structure and low reflection, ≤1%. The samples with shortest (15s) and longest (60s) deposition time had the most promising cross-section structures. However, the intermediate times (30s and 45s) were assumed to have been destroyed when preparation for the cross-section images, making these results misleading. A passivation layer of silicon nitride was deposited with PECVD with four different deposition times; 60, 120, 180 and 240 seconds. The samples with the shortest deposition times (60s and 120s) kept the same low reflection, below 2%, and BSiS after deposition. A passivation layer of alumina was successfully deposited chemically by dip coating and annealing of the wafer at 600°C for 3 hours. Ag plasmonic nanoparticles were mixed into the alumina solution and passivated with the same chemical production steps as the alumina passivation layer without Ag nanoparticles. The Ag nanoparticles was observed and verified with TEM. Low reflection, less than 1%, and the BSiS was kept after deposition of the passivation layer, both with and without Ag nanoparticles.