ShaneLogic/cuinse2-device-fabrication

CuInSe2 Device Fabrication

When to Use

• Fabricating CuInSe2 or Cu(InGa)Se2 (CIGS) thin-film solar cells
• Selecting deposition method for absorber layer formation
• Designing or optimizing device layer stack architecture
• Troubleshooting efficiency issues in chalcopyrite-based devices

Primary Deposition Methods

Method A: Boeing Co-evaporation

1. Set up separate evaporation sources for Cu, In, and Se elements
2. Co-evaporate elements onto heated substrate
3. Control deposition rates to achieve target composition
4. Forms CuInSe2 directly during deposition

Method B: ARCO Solar Precursor Reaction

1. Deposit Cu/In precursor layers onto substrate
2. Perform reactive anneal in H2Se atmosphere
3. CuInSe2 forms through solid-state reaction

Device Layer Stack Construction

Build the device from substrate upward:

1. Substrate Selection

• Early designs: Ceramic substrates
• Modern standard: Soda-lime glass (enables Na diffusion for efficiency gains)

2. Back Contact

• Deposit sputtered Molybdenum (Mo) layer
• Provides stable, conductive rear contact

3. Absorber Layer

• Deposit CuInSe2 or Cu(InGa)Se2 using Method A or B
• Ga incorporation enables bandgap tuning

4. Window Layer

• Deposit CdS buffer layer (optimized thickness: ~50nm)
• Follow with In-doped CdS as current carrier
• Alternative: High-resistance ZnO or ITO for Cd-free designs

5. Front Contact

• Deposit transparent conductive oxide: doped ZnO (preferred) or ITO

Key Process Variables

| Variable | Type | Description | |----------|------|-------------| | cds_thickness | length | CdS layer thickness (evolved from 2μm to optimized 50nm) | | anneal_gas | chemical | Reactive annealing gas (H2Se for precursor method) |

Critical Optimization Notes

• CdS thickness reduction from 2μm to 50nm significantly improved current collection
• Soda-lime glass substrate provides beneficial Na incorporation
• Method selection depends on equipment availability and production scale