Heterojunction Silicon Solar Cell
Fabrication Report
Aditya Gupta
122301002
April 27, 2025
Introduction
This report documents the fabrication process of heterojunction silicon solar cells using
Hot-Wire Chemical Vapor Deposition (HWCVD) technology. The complete characteri-
zation and analysis will be presented in a subsequent report.
1 Fabrication Process
1.1 Substrate Preparation
• Substrate Specification:
– Material: n-type crystalline silicon (c-Si)
– Orientation: <100>
– Thickness: 500 µm
– Growth method: Float-Zone
– Resistivity: 1–10 ·cm
• Surface Preparation:
– Initial cleaning: Standard RCA process
– Oxide removal: 2% HF dip for 30 seconds
1.2 Deposition System Configuration
• Cluster Tool Components:
– Load-lock chamber (base pressure: 10−6 Torr)
– 4 HWCVD reactors (for intrinsic/n-type/p-type a-Si:H)
– 1 RF sputtering chamber (for ITO deposition)
• Process Conditions:
– Substrate temperature: 200-300◦ C
– Deposition pressure: 10−2 -10−1 Torr
1
1.3 Layer Deposition Sequence
1. Front-side intrinsic a-Si:H (6-8 nm)
2. n-doped a-Si:H back surface field (20-25 nm)
3. Wafer flip and HF surface renewal
4. Rear-side intrinsic a-Si:H (6-8 nm)
5. p-doped a-Si:H emitter (14-16 nm)
6. Front ITO deposition (90-100 nm) via RF sputtering
1.4 Metallization Process
• Front Contact:
– Pattern: Finger grid design
– Material: Aluminum (1 µm thickness)
– Deposition: Thermal evaporation through shadow mask
• Rear Contact:
– Full-area aluminum back contact
– Thickness: 2 µm
• Post-Metallization Treatment:
– Sample A (Pol. HIT 525 µm): 300◦ C anneal
– Sample B (Pol. HIT 12): No anneal
2 Material Properties
Table 1: Electrical properties of deposited layers
Layer Precursors Conductivity (S/cm) Carrier Conc. (cm−3 ) Mobility (cm
Intrinsic a-Si:H SiH4 5 × 10−10 4 × 1015 —
p-doped a-Si:H SiH4 + B2 H6 + H2 24 4.2 × 1020 0.386
n-doped a-Si:H SiH4 + PH3 + H2 33 2.5 × 1020 0.8
ITO (TCO) Ar + O2 2.5 × 103 3.6 × 1020 43
2
3 Device Characterization Data
(b) Light IV (with background IV from im-
(a) Dark IV proper contact)
Figure 1: Comparison of Dark and Light IV characteristics for Device 1
3.1 Extracted Solar Cell Parameters
Table 2: Combined Solar Cell and Relevant Diode Parameters
Parameter Symbol Significance and Measurement
Photovoltaic-Specific Metrics
Open-Circuit Voltage VOC Measured at zero current under illumination
2
Short-Circuit Current Density JSC Photocurrent
at zero bias (typically in mA/cm )
VM P P ×JM P P
Fill Factor FF VOC ×JSC
× 100%
Common PN-Junction Parameters
Series Resistance Rs High-current slope of IV curve (Ω·cm2 )
Shunt Resistance Rsh Low-voltage slope of reverse IV (Ω·cm2 )
Saturation Current I0 Dark reverse leakage current density
Junction Capacitance Cj Measured at reverse bias (typically pF)
Table 3: Parameters Extracted from Dark and Light IV Curves (Device 1)
Parameter Symbol Dark IV Light IV
Value Value
Saturation Current I0 8.6 ×10−6 A –
Series Resistance Rs 0.34 / 0.78 0.03
Shunt Resistance Rsh 115.51 4.67
Open-Circuit Voltage VOC – 0.46 V
Short-Circuit Current ISC – 10 mA
Maximum Power Voltage VM P – 0.25 V
Maximum Power Current IM P – 6.75 mA
Fill Factor FF – 37.0%
Area A 160.5564 mm2 160.5564 mm2
Power Input (Given) Pin 100mW 100mW
Power Output Pout 0W 0.624375mW
Efficency η – ≈ 3.89%
3
Abbreviations
Abbreviation Definition
a-Si:H Hydrogenated amorphous silicon
BSF Back surface field
c-Si Crystalline silicon
HWCVD Hot-Wire Chemical Vapor Deposition
ITO Indium Tin Oxide
TCO Transparent Conductive Oxide
4 Plots
Figure 2: Light IV characteristics of the fabricated device.
4
Figure 3: Dark IV characteristics of the fabricated device.
Figure 4: Inverted IV plot for detailed diode behavior visualization.
5 Codes
All the codes are here.
5
Drawing: Solar Cell (Contacts)
15.86 mm
1.78 mm
12.99 mm
0.33 mm
Area Calculation
Top rectangle area:
Areatop = 15.86 × 1.78 = 28.2308 mm2
Single rod area:
Areaone rod = 12.99 × 0.5 = 6.495 mm2
Total rods area (7 rods):
Arearods = 7 × 6.495 = 45.465 mm2
Total Area:
Total Area = 28.2308 + 45.465 = 73.6958 mm2
Total Area of Solar Cell:
Total AreaSolar Cell = 234.2522 − 73.6958 = 160.5564 mm2
Efficency Calculations
• Area of the solar cell, A = 160.5564 mm2 = 160.5564 × 10−6 m2
• Fill Factor, F F = 37% = 0.37
• Open-circuit voltage, Voc = 0.25 V
• Short-circuit current, Isc = 6.75 mA = 0.00675 A
• Incident light power density = 100 W/m2
6
Step 1: Maximum Power Output
The maximum power output Pmpp is given by:
Pmpp = F F × Voc × Isc
Substituting the given values:
Pmpp = 0.37 × 0.25 × 0.00675
Pmpp = 0.37 × 0.0016875
Pmpp = 0.000624375 W
Pmpp = 0.624375 mW
Step 2: Input Power
The input power Pin is:
Pin = Irradiance × A
Pin = 100 × 160.5564 × 10−6
Pin = 0.01605564 W
Step 3: Efficiency Calculation
The efficiency η is:
Pmpp
η= × 100
Pin
Substituting:
0.000624375
η= × 100
0.01605564
η ≈ 3.89%
Final Result:
• Maximum Power Output: 0.624375 mW
• Efficiency: η ≈ 0.389%
