Investigation of a-Si:H solar cells with a protocrystalline-like amorphous silicon intrinsic layer
We investigate the effects of the hydrogen dilution in a-Si:H film on the crystallization and the absorption property. Crystallization of the a-Si:H films from amorphous to several tens nanometer-sized crystal state is observed by increase of hydrogen dilution ratio using PECVD. The phase transition of the a-Si:H films from amorphous to micro-crystal occurred very rapidly in a very narrow range of the silane concentration(SC). Protocrystalline-like properties of silicon (pc-Si:H) is obtained fractionally within the a-Si:H matrix. It could be assumed that the volume fraction of the protocrystalline silicon is the highest in the range of SC=3.7∼4.0%, whereas amorphous or micro-crystalline phases are dominant in the other range of SC<4.0% and SC>3.0%, respectively. The μc-Si:H films with SC=1.0%~1.4% have the micro-crystalline volume fraction 75%∼80%. But the μc-Si:H films still contain the amorphous, proto- or nano-crystalline silicon in the rest volume so that they show some different characteristics with other micro-crystalline silicon. The a-Si:H films with SC=3.7∼4.0% doesn't contain the micro-crystalline volume fraction but different characteristics in absorption from the other a-Si:H films with higher SC>4.0%. Such films could be assumed to have the properties of the protocrystalline silicon. They, consequently, showed the low degradation property from the light soaking and the rapid stability.
Hot-wire chemical vapor-deposited microcrystalline silicon in single and tandem n–i–p solar cells
Abstract This paper examines the potential of μc-Si deposited by hot-wire chemical vapor deposition (HWCVD) at a constant hydrogen dilution of 0.95, as absorber layer in n–i–p thin film solar cells. For a series of single junction cells onto plain stainless steel, the highest open circuit voltage (Voc) and Fill Factor (FF) were 0.54 V and 0.72. From J–V measurements at reduced light intensities, the change of the AM1.5-normalized FF values with light intensity was found to depend on the μc-Si i-layer thickness. This is attributed to the thickness evolution of the i-layer crystallinity, which influences the cell properties, particularly for i-layers thinner than 2.0 μm. For thicker layers the measurements clearly show drift-driven charge carrier collection. Tandem cells showed FF values as high as 0.77, which indicates the very high optoelectronic quality of the μc-Si material. A 2.0 μm cell on a textured back reflector shows an efficiency of 7.8%.
The Politics of Truth: Power in Nietzsche’s Epistemology
This article concerns first a curiosity found in Friedrich Nietzsche’s The Antichrist. In the midst of a heated attack on Christianity, Nietzsche detours into a discussion of epistemology. I argue that this turn indicates the importance of epistemology, and illustrates its political and moral character. The weak, who cannot tolerate uncertainty and shades of gray, seek to impose an epistemology of clarity and certainty. At the same time, the strong, who revel in ambiguity, seek to enjoy the richness and subtlety of a non-dichotomous view of the world. This is a political struggle because the weak cannot allow the strong’s epistemology to exist, let alone prevail. It is not surprising, then, that Nietzsche talks about epistemology in the midst of attacking Christianity: its view of truth is essential to its mission of taming the nobles. Here, I consider Nietzsche as a political thinker in a different light. Political battles are fought far beyond the halls of government. Nietzsche is a political thinker; one, however, who looks at politics in an uncommon way.