Light induced electrical and macroscopic changes in hydrogenated polymorphous silicon solar cells

Abstract

We report on light-induced electrical and macroscopic changes in hydrogenated polymorphous silicon (pm-Si:H) PIN solar cells. To explain the particular light-soaking behavior of such cells -namely an increase of the open circuit voltage (Voc) and a rapid drop of the short circuit current density (Jsc) -we correlate these effects to changes in hydrogen incorporation and structural properties in the layers of the cells. Numerous techniques such as current-voltage characteristics, infrared spectroscopy, hydrogen exodiffusion, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and spectroscopic ellipsometry are used to study the light-induced changes from microscopic to macroscopic scales (up to tens of microns). Such comprehensive use of complementary techniques lead us to suggest that light-soaking produces the diffusion of molecular hydrogen, hydrogen accumulation at p-layer/substrate interface and localized delamination of the interface. Based on these results we propose that light-induced degradation of PIN solar cells has to be addressed from not only as a material issue, but also a device point of view. In particular we bring experimental evidence that localized delamination at the interface between the p-layer and SnO2 substrate by light-induced hydrogen motion causes the rapid drop of Jsc.

Light‐Induced Reversible Optical Properties of Hydrogenated Amorphous Silicon: A Promising Optically Programmable Photonic Material

“…It was postulated that a reversible change in refractive index by 1–3% is possible. Recently, similar reversible light‐induced behavior has been reported by Kim et al Furthermore, Kuyken et al showed that the non‐linearity of a ‐Si:H nanowire waveguides was unstable during the characterization with a pump‐probe technique at 1550 nm. Surprisingly, this phenomenon can be reversed after annealing at 200 °C for half an hour and this can be continued in cycles.…”

Comparison of amorphous silicon absorber materials: Kinetics of light‐induced degradation

“…A possible interpretation is that the polymorphous silicon suffers less from light‐induced degradation than standard amorphous silicon. This is in agreement with specific literature on pm ‐Si:H and generally observed for materials that are deposited close to the transition between a ‐Si:H and μ c ‐Si:H (cf. Section 5).…”

Boron doping compensation of hydrogenated amorphous and polymorphous germanium thin films for infrared detection applications

“…Moreover, polymorphous semiconductors represent a technological advance in the development of IR sensing films, since this kind of materials is more stable against the incident radiation than amorphous semiconductors [8][9][10][11][19][20][21], which are currently used as sensing films in commercial IR detector arrays [4].…”

“…The better stability of polymorphous semiconductors over the amorphous counterpart has been demonstrated in the fabrication of thin solar cells [19][20][21], where it has been shown that due to radiation (light soaking) the amorphous film solar cells suffer of degradation and its efficiency is reduced from an initial value, while for polymorphous solar cells the degradation is lower. That degradation is related to weak bonds and stress in the material.…”