Effects of oxygen incorporation in solar cells with a-SiO_x:H absorber layer

Abstract

The effects of oxygen incorporation on layer properties and cell performance were investigated in thin film solar cells with a-SiOx:H absorber layers. Besides the widened optical band gap and increased defect densities, a doping effect is observed upon oxygen incorporation even for the layers with wide band gap. From comparison of solar cells illuminated from either p- or n-side, we conclude that overall hole carrier collection is strongly deteriorated by increasing the oxygen concentration. The donor-like states induced by oxygen reform the electric field in the absorber. The intensified electric field near the p/i interface improves the quantum efficiency (QE) around 400 nm, which is attributed to the better carrier collection in the p-layer. The maximum of QE shows a blue shift with both p- and n-side illumination. It is consistent with the enhanced optical band gap of the absorber layer and shows the potential of usage in multi-junction solar cells.

Comparison of silicon oxide and silicon carbide absorber materials in silicon thin-film solar cells

“…Yet the films prepared with CO 2 show higher photoconductivity by half an order of magnitude compared to CH 4 which seems to contradict our remaining results. Figure 10 shows the activation energy calculated from the dark conductivity at room temperature with a constant conductivity prefactor of σ 0 = 150 S/cm as proposed in reference [18]. The activation energy increases with the Tauc bandgap and takes slightly lower values for samples prepared with CO 2 compared to those prepared with CH 4 .…”

“…Another explanation for the discrepancy between photoconductivity and cell results could be that cell performance also depends on hole carrier transport which is not monitored by our conductivity measurements. Wang et al report that hole carrier collection is strongly deteriorated with increased oxygen concentration of amorphous silicon oxide absorber layers in single cells [18]. So it is possible that silicon carbide allows better hole carrier transport than silicon oxide at equivalent bandgaps when used as absorber layers in amorphous silicon single cells.…”

Influence of ZnSnO x barrier layer on the texturing of ZnO:Al layers for light management in flexible thin-film silicon solar cells

“…The plasma might damage the PET substrate , dissolving contaminating atoms like carbon or oxygen from the substrate, which are subsequently incorporated into the silicon layers. Incorporation of these atoms may cause additional electronic defects, reducing the photoelectronic quality of the silicon layer, which consequently would impede the charge carrier collection efficiency . Furthermore, PET is known to be permeable to water and oxygen , so without a diffusion barrier such as ZnSnO x , impurities may also enter the silicon layers though the PET substrate.…”

Tuning of the open-circuit voltage by wide band-gap absorber and doped layers in thin film silicon solar cells

“…The dark conductivity σ d and optical gap E 04 of the ⟨p⟩ layers were measured (more details about the measurements could be found in the Ref. ). By assuming the mobility band gap E g = E 04 , a quantity Δ E p is defined as given as the difference between the band gap and activation energy in the ⟨p⟩ layers.…”