Innovative structures for thin film crystalline silicon solar cells to give high efficiencies from low quality silicon

Abstract

The multilayer cell has been specifically designed with the aim to obtain high solar cell efficiency using low quality, thin film, polycrystalline silicon material. The structure consists of multiple p-and n-type silicon layers. This paper examines the tolerance of the cell design to a range of metallic impurities and grain boundaries using computer simulations. The modelled results indicate that the device can tolerate impurity concentrations up to 250 times greater than a conventional, thick solar cell. Further, the results indicate that the structure has excellent tolerance to grain boundaries present in bulk regions of the device. The simulations indicate that grain boundaries present in depletion regions will limit efficiencies considerably if the effective recombination velocity of the grain boundary approaches 10 % cm/s. This extreme case should be largely avoided utilizing grain boundary passivation techniques during device fabrication.

Radial PN junction, wire array solar cells

“…The design was predicted to have superior tolerance to metallic impurities as well as to grain boundaries. [27] However, detractors claimed that, if one includes the effects of efficient light trapping, the parallel multijunction design is little better than a planar design, if at all. [29] It is not altogether clear from the literature why work on this design ceased, as relatively efficient (∼ 13%) cells had been shown to be manufacturable with deposited Si in an industrial-like environment.…”

“…[30] [31] However, it is likely tied to cost effectiveness, i.e., that the cell did not perform well enough to justify the expense of the single-crystalline growth substrate necessary for high quality Si device layers. [27]). …”