H2-Dilution vs. Buffer Layers for Increased Voc

Abstract

AbstractHydrogen dilution and buffer layers, as two ways to obtain higher Voc values in a-Si:H p-i-n solar cells, are directly compared in the present study. Special emphasis is laid on stability against light soaking. H2-dilution in combination with lower substrate temperature yields higher Voc values and better stability as compared to buffer layers. However, light absorption is decreased due to the increased gap in H2-diluted cells. The stability of buffer layer cells can remarkably be ameliorated by boron doping and H2-dilution of the a-SiC:H buffer layer. However, stabilized efficiency is higher for optimized diluted cells than for cells with a buffer layer. An a-Si/a-Si stacked cell with a graded dilution for both cells yielded 10% initial efficiency with 17% relative degradation. Diluted a-Si:H cells at lower temperature become specially interesting in combination with a microcrystalline bottom cell. For such a “micromorph” tandem cell we obtained 11.4% initial efficiency.