Precise dopant detection and transport properties of boron ion-implanted silicon solar cells

Abstract

Silicon solar cells continue to dominate photovoltaic technology, holding a market value of ∼98% with an efficiency of 13–24% at the commercial level, which is limited by the recombination process and generated defects during the fabrication process. This study presents p–n junction fabrication using the ion beam technology, where boron species are implanted at a low energy of 35 keV into n-type Si (100). Doping was confirmed by X-ray photoelectron spectroscopy (XPS), which outperformed other conventional techniques (RBS and XRD) with exceptional elemental detection sensitivity. The shift in binding energy was observed to be 0.24 eV for the main peak in the silicon 2p spectra, resulting from the incorporation of boron into the silicon lattice. The local electronic environment modification was investigated by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the O K-edge, which showed local hybridization consistent with boron incorporation and was also validated by FEFF simulations. Moreover, transport measurements exhibited diode-like I–V characteristics obtained using linear sweep voltammetry that were consistent with the Shockley diode model, indicating the formation of a p–n junction and notable suppression of the leakage current to 0.63 µA. Collectively, these findings evidence that the ion beam technology is a viable approach for the fabrication of reduced-defect structures, which are essential for the advancements of photovoltaics.