Fig. 4: The short-circuit current density (J_SC) loss analysis in HBC solar cell.

a External quantum efficiency (EQE) spectrum with two different test area. Inset shows the schematic diagram of the current density loss channels in HBC cell from the optics (J_front and J_rear) and recombination (J_shade). Where the minority carrier (holes) upon ESC region has longer transport length (L₂), compared to those upon HSC region (L₁), to the collection region (i.e., HSC). Thus, recombination will be easier occurred in the path, leading to current density loss (electrical shade loss). b The demonstration of electrical shading phenomenon by simulation using Quokka software. It shows a smallest unit of the device (like the inset of Fig. 4a), where semi-transparent red color and semi-transparent blue color represent the HSC region and non-collection region (i.e., gap and ESC region), respectively. The upper panel is the internal quantum efficiency (IQE) as a function of device length under different surface recombination of gap and ESC region (S_{ESC, gap}), and bottom panel is the spatial map of current flow in device under 1 sun illumination for the case of S_{ESC, gap} = 64 cm·s⁻¹. Where the colored arrows in bottom panel represent the hole current density with intensity (J_hole). c The measurement of light beam induced current (LBIC) at the wafer edge portion of our HBC solar cell with three different positions (marked as edge 1, edge 2, and edge 3). The upper panel shows the photography of rear surface of solar cell corresponding to the test area, while the middle panel is the amplification information corresponding to the dashed box in bottom panel. d The recombination current density (J_rec) as functions of effective lifetime (τ_eff) and transport length. Insert is the diagram of simulated structure. The τ_bulk and J_gen represent the silicon bulk lifetime and photo-generated current density. Source data are provided as a Source Data file.