simulation-verification-and-comparison

name: simulation-verification-and-comparison description: Compare simulation results between Driftfusion and other simulators (ASA, IonMonger), analyze discrepancies in J-V characteristics, and configure simulations for fair comparison.

Simulation Verification and Comparison

Use this skill when you need to:

• Compare Driftfusion results with ASA or IonMonger simulators
• Analyze discrepancies in J-V characteristics between simulators
• Configure simulations for fair comparison
• Identify variance sources and apply mitigation strategies

ASA Comparison Configuration

When to use: Comparing Driftfusion results with ASA tool

Configuration Steps:

1. Discretization Setup:

   • Set linear grid spacing for ASA: 1 nm
   • Set interface thickness in Driftfusion: 1 nm

2. Optical Model:

   • Select Beer-Lambert option (without back contact reflection)
   • Use identical optical constant and photon flux density spectrum data
   • Alternative: Insert generation profile from ASA into Driftfusion parameters

3. J-V Scan Settings:

   • Scan range: $V_{app} = 0$ to 1.3 V
   • Scan rate: $k_{scan} = 10^{-10}$ V/s
   • Reason: Minimizes displacement current for fair comparison with steady-state ASA solver

Simulator Discrepancy Analysis

When to use: Comparing simulation results for devices with varying conduction band properties

Calculation: $$\text{Percentage Difference} = 100 \times \frac{J_{ASA} - J_{DF}}{J_{ASA}}$$

Analysis Guidelines:

Parameter Set 1 (PS1):

• Expected difference: ~1% for $J > 10^{-12}$ A cm⁻²
• Halving active layer thickness has minimal impact

Parameter Set 2 (PS2):

• Expected difference: Up to ~5% for $J > 10^{-12}$ mA cm⁻²
• Root causes:
  • Electron density change > 7 orders of magnitude at absorber-ETL interface
  • eDOS transition: $N_{CB} = 10^{18}$ to $10^{20}$ cm⁻³
  • Conduction band energy change: 0.3 eV

Mitigation: Use uniform eDOS ($N_{CB} = 10^{18}$ cm⁻³) across all layers

Three-Layer Device Methodology Comparison

IonMonger Approach:

• Abrupt interfaces
• Solves 8 variables simultaneously
• Only holes in HTL, only electrons in ETL
• Boundary conditions evaluate interfacial recombination at same grid point

Driftfusion Approach:

• Discrete interlayer interface approach
• Solves 4 variables simultaneously
• All carriers resolved in all regions
• Ionic carrier mobility = 0 in HTL, ETL, and interfaces
• Ionic charge compensated by static background charged density

Variance Sources and Mitigation

Primary Variance Sources:

• Treatment of electronic currents across interfaces
• Spatial mesh differences
• Ionic carrier density calculation (Driftfusion: all layers; IonMonger: not all)

Interfacial Recombination Errors:

• Volumetric surface recombination scheme introduces errors
• Surface carrier density differences (electron density at active layer-HTL interface)
• Errors increase with energetic barriers (0.4 to 0.8 eV)

Mitigation Strategies:

1. Increase interface thickness
2. Use more interface mesh points

Trade-off: Increased thickness sacrifices consistency with analytical models using abrupt interfaces, but provides greater flexibility.