---
name: cdte-cell-degradation-analysis
description: Diagnose and manage degradation in CdS/CdTe solar cells under stress conditions. Use when evaluating CdTe cell stability, diagnosing Voc loss, analyzing back contact issues, planning accelerated lifetime testing, or investigating copper-related degradation in CdTe devices.
---

# CdTe Cell Degradation Analysis

## When to Use
- Evaluating CdS/CdTe cell stability under stress conditions
- Diagnosing unexpected Voc loss in CdTe cells
- Analyzing back contact degradation issues
- Planning accelerated lifetime testing protocols
- Investigating copper-related degradation in back contacts

## Degradation Assessment

### Normal Operating Conditions
CdS/CdTe cells are relatively stable under:
- Normal day/night outdoor cycles
- Operation near maximum power point
- Standard operating temperatures

### Stress-Induced Degradation
**Trigger conditions:**
- Constant full illumination (AM1) at elevated temperatures
- Open circuit voltage condition (worst case)

**Symptoms:**
- Substantial decrease in open circuit voltage (Voc)
- ~80mV Voc loss per month at 100°C, AM1, open circuit
- I-V curve bending at higher bias
- Reduced rectification in dark characteristics
- Dark current shifts to higher values

### Degradation Location
Primary site: Back contact region
- Evidence: Dark current degradation, diode effect reduction
- Mechanism: Copper diffusion/migration likely cause

## Recovery Procedures

### Recovery Conditions
1. Return cell to short circuit load
2. Store in dark conditions
3. Duration: Few days for nearly full recovery

### Recontacting (Partial Recovery)
If recovery is insufficient:
1. Etch off back electrode
2. Apply new back contact
3. Result: Partial restoration of characteristics
4. Note: Some Voc degradation may persist permanently

## Back Contact Optimization

### Copper Thickness Guidelines
- **Dark characteristics**: Need ≥15nm Cu for reasonable initial diode behavior
- **Illuminated characteristics**: ≥2nm Cu sufficient
- **Trade-off**: Thicker Cu may accelerate degradation

### Processing Methods
- Dry (evaporation) vs. wet (etching) processing affects degradation rates
- Optimize for target lifetime requirements

## Production Stability Targets
- Large panels (>1 m²): Edge-to-edge efficiencies >10%
- Life expectancy: >10 years at >80% initial performance