Improvement in Surface Passivation of c-Si Using Gradient-Layered a-Si:H Film for High Efficiency Silicon Heterojunction Solar Cells

Gradient-layered
$i$
a-Si:H passivation is shown to enhance minority carrier lifetimes in silicon heterojunction solar cells compared to single or dual-layer passivation structures. The gradient layered passivation contains optimized interfacial and capping layers for passivating the
$i$
a-Si:H/c-Si interface and a gradient layer for suppressing charge traps in bulk
$i$
a-Si:H. Gradient layers were obtained by changing the hydrogen dilution ratio continuously during deposition of
$i$
a-Si:H. The minority carrier lifetime of the c-Si substrate using gradient-layered passivation was as high as
$2451\mu \mathbf{s}$
, compared to 1831 μs for dual-layered passivation at
$2\times 10^{15}$
cm
⁻¹
injection level. JV characteristics of Silicon heterojunction (SHJ) solar cell employing these gradient passivation schemes will also be discussed. When the gradient-layered passivation was implied to interdigitated back contact (IBC) SHJ solar cells, there was an improvement in efficiency, compared to other passivation schemes such as single and dual passivation.