Solar cells on low-resistivity boron-doped Czochralski-grown silicon with stabilized efficiencies of 20%

Abstract

Recently, it was shown that the boron-oxygen complex responsible for the light-induced lifetime degradation in oxygen-rich boron-doped silicon can be permanently deactivated by illumination at elevated temperatures. Since the degradation is particularly harmful in low-resistivity Czochralski silicon (Cz-Si), we apply the deactivation procedure to a high-efficiency rear interdigitated single evaporation emitter wrap-through solar cell made on 1.4Ωcm B-doped Cz-Si. The energy conversion efficiency is thereby increased by more than 1% absolute compared to the degraded state to 20.3% on a designated area of 92cm2 and is furthermore shown to be stable under illumination at room temperature.

Advances in crystalline silicon solar cell technology for industrial mass production

“…Many studies have been undertaken in attempts to eliminate LID eff ects in monocrystallinesilicon PV cells, and permanent deactivation of the complex at high temperature (> 170 °C) has been reported [18]. Boron-doped magneticfi eld CZ wafers and gallium-doped CZ wafers also show promise for eliminating LID eff ects in monocrystalline solar cells, and CZ-silicon cells based on phosphorous-doped n-type CZ wafers are also free of LID eff ects.…”

Development of industrial high‐efficiency back‐contact czochralski‐silicon solar cells

“…The desire for lower resistivity must be balanced with the enhanced LID, although LID is anticipated to be reduced in EWT cells due to the dual‐side collection of carriers in the n + pn + region of the cell. Alternatively, LID may be mitigated through use of Ga doping, low‐O content Si, or regeneration anneal 11. Cell designs for different resistivity ranges have been developed and their use in cell fabrication is underway.…”

Progress in emitter wrap-through solar cell fabrication on boron doped Czochralski-grown silicon

“…In 2007 we published an 'advanced' RISE-EWT cell structure (including a full area rear side SiO 2 -passivation with local emitter contact openings and selective emitter diffusion) using the same material and cell size with an efficiency of 21.4% (since then independently confirmed) [3]. With the same 'advanced' cell structure on industrially relevant Cz-Si we achieved and published in 2008 a stabilised conversion efficiency of 20.3% [4]. (Some months later than Ref.…”

“…(Some months later than Ref. [4] the cell was measured again, this time independently at ISE-CalLab, yielding an efficiency of 19.8%). The degradation of this solar cell due to the formation of recombination-active boron-oxygen complexes under illumination [5,6] was deactivated.…”