Atomic Layer Deposition-Based Ultrathin SnO x Buffer for High Passivation Quality in Silicon Heterojunction Solar Cells

초록

Tin oxide (SnO x ) layers fabricated via atomic layer deposition (ALD) effectively serve as electron transport or sputter-resistant buffer layers in perovskite, silicon, and tandem solar cells, mitigating the interface defect density induced by transparent conductive oxide (TCO) in heterojunction (HIT) photovoltaic devices. This study introduces a 7 nm SnO x layer between P-doped amorphous Si (n-a-Si:H) and TCO to significantly enhance the minority carrier lifetime (MCLT). The incorporation of SnO x increased the MCLT of silicon wafers by approximately 32.5%, from 1328 to 1760 mu s, measured at an excess carrier density of 1.0 x 1015 cm-3. UV-visible spectroscopy analysis determined the SnO x film bandgap to be 3.48 eV, facilitating effective absorption of plasma-induced radiation and substantially reducing damage during TCO deposition. X-ray photoelectron spectroscopy (XPS) reveals that SnO x (x approximate to 1.8) exhibits n-type conductivity, effectively passivating n-a-Si:H and mitigating plasma damage, enhancing MCLT. Consequently, the optimized photovoltaic device achieved superior performance, exhibiting a short-circuit current density (J sc) of 40.84 mA/cm2, an open-circuit voltage (V oc) of 728 mV, a fill factor (FF) of 80.53%, and an overall power conversion efficiency (PCE) of 23.95%. These findings underscore the potential of ultrathin SnO x layers to enhance both efficiency and durability of advanced silicon-based solar cells.

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