Light-induced metastability in hydrogenated nanocrystalline silicon solar cells

Abstract

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells has been studied under different light spectra. The nc-Si:H studied contains a certain fraction of hydrogenated amorphous silicon (a-Si:H). We observe no light-induced degradation when the photon energy used is lower than the bandgap of a-Si:H, while degradation occurs when the photon energy is higher than the bandgap. We conclude that the light-induced defect generation occurs mainly in the amorphous phase. Light soaking experiments on a-Si:H∕a-SiGe:H∕nc-Si:H triple-junction solar cells show no light-induced degradation in the bottom cell, because the a-Si:H top and a a-SiGe:H middle cells absorb most of the high-energy photons.

Kinetics of creation and of thermal annealing of light-induced defects in microcrystalline silicon solar cells

“…Previous works demonstrated that some c-Si: H solar cells present a milder form of light-induced degradation, depending on the crystalline volume fraction. [12][13][14][15][16][17][18][19] Klein et al 12 reported a relative decrease of the conversion efficiency of up to 10% after 1000 h of degradation for highly amorphous c-Si: H solar cells; we confirmed, by studying dilution series of c-Si: H solar cells, that the higher the crystallinity, the lower the relative drop in efficiency. 13 Yan et al investigated the influence of the illumination spectra on the lightinduced degradation, 14 as well as the influence of the electrical bias.…”

“…[12][13][14][15][16][17][18][19] Klein et al 12 reported a relative decrease of the conversion efficiency of up to 10% after 1000 h of degradation for highly amorphous c-Si: H solar cells; we confirmed, by studying dilution series of c-Si: H solar cells, that the higher the crystallinity, the lower the relative drop in efficiency. 13 Yan et al investigated the influence of the illumination spectra on the lightinduced degradation, 14 as well as the influence of the electrical bias. 15 They initially concluded that the amorphous phase was solely responsible for the light-induced degradation observed in c-Si: H. Nevertheless, they lately suggested that small grains and/or intermediate-range order could as well play an important role regarding the stability of c-Si: H solar cells.…”

Influence of the statistical shift of Fermi level on the conductivity behavior in microcrystalline silicon

“…In spite of the immense potential of high efficiencies and large area deposition capabilities shown by µc-Si:H in semiconductor technology, especially in photovoltaics 24,25 and TFTs, 26 the understanding of its transport properties is impeded by these lacunae. Different conduction mechanisms and paths have been invoked to explain the electrical transport behavior in µc-Si:H, deriving information that correlate only some microstructural features and mechanisms.…”

Alternative designs for nanocrystalline silicon solar cells

“…This is attributed to the passivation properties of amorphous tissue which surround the grain boundaries. But an increased amorphous concentration in the intrinsic layer leads to degradation in the electronic properties of the device, under prolonged light exposure [133,134,135,136].…”