Abstract
Thermal oxide (SiO2) and hydrogen-rich amorphous silicon (a-Si:H) interlayer at the front metal-silicon contact of thin silicon solar cells has been optimized based on a theoretical model. An analytical solution to the complete set of equations has been provided to highlighted the potential use and implications of the a-Si:H/SiO2 as a passivation coating at the front surface in crystalline silicon solar cells. The simple analytical expressions of the emitter reverse saturation current density and the photocurrent density were also obtained taking into account bulk recombination velocity and non-uniform doping profile. An optimum a-Si:H/SiO2 interlayer thicknesses were noted to enhance the collection of light-generated free carriers, which improves the efficiency of the short wavelength quantum. This is achieved by a drastic reduction in the effective recombination at the emitter upper boundary, a properly primarily responsible for the decrease in the emitter saturation current density. The findings indicated that the emitter region should be treated as an active layer because an optimum a-Si:H/SiO2 interlayer thicknesses at the front contact (W n,1 = 5 nm and δ = 14 Å) give an improvement that can reach 3.6 mA/cm2 for the photocurrent density, 63 mV for the open-circuit voltage, and 3.95% for the cell efficiency.
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Abbreviations
- q :
-
Electron charge
- V T :
-
Thermal voltage
- W n,1 (W n,2):
-
a-Si:H (c-Si) emitter thickness
- W P (W):
-
Base (depletion layer) thickness
- δ :
-
Interfacial oxide thickness
- S p (S n ):
-
Front (back) surface recombination velocity
- S iR (S iL ):
-
Hole recombination velocity at c-Si emitter (a-Si:H) side
- T iR (T iL ):
-
Interface blocking factor on the c-Si (a-Si:H) side
- S amor (S mono):
-
Effective recombination velocity relative to the a-Si:H (c-Si) region
- S peff,R (S peff,L):
-
Effective recombination velocity at the right (left) of the oxide layer
- p0,1(x) (p0,2(x)):
-
Hole concentration at equilibrium in the a-Si:H (c-Si)
- α 1,λ (α 2,λ ):
-
a-Si:H (c-Si) absorption coefficient
- ϕ0λ :
-
Photon flux density
- R λ :
-
c-Si reflectance
- D peff,1 (D peff,2):
-
Average hole diffusion coefficient in the a-Si:H (c-Si) emitter
- L peff,1 (L peff,2):
-
Average hole diffusion length in the a-Si:H (c-Si) emitter
- τ peff,1 (τ peff,2):
-
Average hole lifetime in the a-Si:H (c-Si) emitter
- u L1 :
-
Light-generated normalized excess hole density in the a-Si:H emitter
- \(J_{ph}^{{{\text{n}},a{\text{ - Si}}}} \left( \lambda \right)\) :
-
Light-generated hole current density in the a-Si:H emitter
- \(J_{ph}^{\text{n}} \left( \lambda \right)\) :
-
Light-generated hole current density in the c-Si emitter
- \(J_{ph}^{\text{p}} \left( \lambda \right)\) :
-
Light-generated hole current density in the base region
- \(J_{ph}^{\text{w}} \left( \lambda \right)\) :
-
Light-generated hole current density in the depletion layer
- \(J_{ph}^{{{\text{a}} - {\text{c}}}} \left( \lambda \right)\) :
-
Total light-generated current density of the passivated solar cell
- \(J_{ph}^{\text{c}} \left( \lambda \right)\) :
-
Total light-generated current density of the conventional solar cell
- \(J_{{0{\text{E}}}} \left( {J_{0E}^{{{\text{a}} - {\text{c}}}} } \right)\) :
-
Emitter dark saturation current density for metal (a-Si:H) contacted devices
- ΔJ ph :
-
Increase in total light-generated current density
- ΔV oc :
-
Increase in open-circuit voltage
- Δη :
-
Increase in conversion efficiency
- F a−c :
-
Amorphous–crystalline factor
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Bougoffa, A., Trabelsi, A., Zouari, A. et al. A new modeling approach for amorphous silicon passivated front contact for thin silicon solar cells. Opt Quant Electron 49, 259 (2017). https://doi.org/10.1007/s11082-017-1093-5
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DOI: https://doi.org/10.1007/s11082-017-1093-5