Figure 1

Energy band diagram drawn to scale for a short-circuited multi-layer solar cell based on p-type window material (p⁺-p-i-n–n⁺ structure). P⁺ and n⁺ layers act as electron back diffusion barrier (ebdb) layer (or Hole Transport Layer- HTL), and hole back diffusion barrier (hbdb) layer (or Electron Transport Layer- ETL) respectively.