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SOLEY

SOLEY - Solar Cell Simulation Package

A scientific-grade toolkit for optical and electrical modelling of photovoltaic devices

Overview

SOLEY is a simulation platform for researchers and engineers working on photovoltaic device optimisation. Unlike traditional drift-diffusion simulators, SOLEY implements an extended detailed balance framework combined with rigorous Transfer Matrix Method (TMM) optical calculations, offering a complementary approach to existing tools like SCAPS-1D or PC1D.

Why SOLEY?

Thermodynamically Consistent

Built on detailed balance principles ensuring physical accuracy

Multi-Junction Support

Native support for tandem and multi-terminal configurations

Bulk and Interface defects

Customisable recombination pathways

Fast & Parallel

TMM calculations with generation profile export

Luminescence Spectroscopy

Integrated PL/EL for material characterization

Design Exploration

Quick parameter screening and optimization

Key Features

Optical Simulation Capabilities

Transfer Matrix Method (TMM) Engine
  • Rigorous electromagnetic modelling of multilayer thin-film stacks
  • R, T, and layer-by-layer absorptance calculation
  • Field distribution for generation profiles
  • Complex refractive index support (n + ik)
  • Wavelength range: 250–4000 nm
Advanced Illumination
  • Direct light with variable incidence angle (0–89°)
  • Diffuse illumination with Lambertian weighting
  • Polarisation control: TE, TM, unpolarised
  • Custom spectral input (AM1.5G, indoor, etc.)
  • Dynamic injection control (0.001–46,300 suns)
Material Handling
  • Bruggeman EMA for composite layers
  • Real-time bandgap extraction
  • Arbitrary material combinations
  • Built-in smoothing algorithms

Device Physics & Electrical Modelling

Extended Detailed Balance
  • Shockley-Queisser limit calculations
  • Radiative recombination (Van Roosbroeck-Shockley)
  • SRH with bulk and interface recombination
  • Auger recombination with T and Eg dependence
  • TMM-integrated absorption spectra
Multi-Junction Support
  • 2-terminal tandem calculations
  • Current-matching analysis
  • 4-terminal efficiency summation
  • Support for 3–6 junction devices
  • Automatic limiting-subcell ID
Defect Modelling
  • Microscopic parameter input (Nt, σn, σp)
  • Automatic J₀ calculation
  • Activation energy (Ea) specification
  • Per-absorber storage

Analysis & Characterization Tools

J-V Characteristics
  • Dark and illuminated curves
  • Custom voltage sweep range
  • Multi-absorber overlay
  • CSV export
Luminescence (PL/EL)
  • Van Roosbroeck-Shockley emission
  • Variable excitation wavelength/power
  • Applied voltage control
  • TMM-based absorptivity
  • Quasi-Fermi splitting calculations
SQ Limit Calculator
  • Theoretical efficiency limits
  • Auger recombination inclusion
  • Resistance effects
  • Temperature-dependent
  • Concentration effects
External Quantum Efficiency
  • Thermodynamic EQE model
  • J₀ to lifetime mapping
  • Green's function approach
  • TMM field integration

Application Screenshots

See SOLEY in action with these interface examples:

💡 Tip: Start with the example files included in the download to familiarize yourself with the workflow before building your own device structures.

Download SOLEY v1.5

Choose your platform below. All packages include the full application, example files, and user manual.

🪟
Windows

~100 MB

Download for Windows

Windows 10/11 (64-bit)

🍎
macOS

~60 MB

Download for macOS

macOS 10.15+ (Intel/Apple Silicon)

🐧
Linux

~100 MB

Download for Linux

Ubuntu 20.04+ / Debian-based

📦 What's included:
  • SOLEY executable application
  • Example device structures
  • Sample optical constants database
  • User manual (PDF) should be downloaded separately on Zenodo

System Requirements

  • OS: Windows 10/11, macOS 10.15+, or Ubuntu 20.04+
  • RAM: 4 GB minimum (8 GB recommended)
  • Disk Space: 500 MB free space
  • Display: 1280×720 minimum resolution

Previous Versions

All releases are archived on Zenodo with DOI versioning.

Quick Start Guide

Installation

  1. Download the appropriate package for your operating system
  2. Extract the ZIP archive to your desired location
  3. Run the SOLEY executable (no installation required)
⚠️ macOS Users: You may need to right-click the application and select "Open" the first time due to Gatekeeper security. Go to System Preferences → Security & Privacy if blocked.

First Simulation in 5 Steps

1. Load Example Structure

File → Open → Select "perovskite_silicon_tandem.soley"

2. Run Optical Calculation

Click "Calculate TMM" to compute absorption profiles

3. Set Device Parameters

Navigate to "Device Physics" tab and review recombination settings

4. Generate J-V Curve

Tools → J-V Characteristics → Select illumination conditions

5. Export Results

File → Export → Choose CSV or PNG format

Essential Workflow

1. Define layer stack (materials + thicknesses)
2. Assign optical constants (n, k data)
3. Run TMM calculation
4. Set absorber parameters (Eg, defects, etc.)
5. Choose illumination (spectrum, angle, intensity)
6. Run electrical model (J-V, EQE, PL, etc.)
7. Analyze and export results

Example Files Included

  • single_junction_silicon.soley - Basic c-Si device
  • perovskite_silicon_tandem.soley - 2T tandem cell
  • CZTS.soley - Sulphur Kesterite
  • CZTSe.soley - Selenium Kesterite

Getting Help

Consult the full User Manual (PDF) for detailed tutorials and parameter explanations.

Technical Approach

Optical Model: Transfer Matrix Method

SOLEY implements the Fresnel-based TMM for stratified media:

  • Exact solution of Maxwell's equations in planar geometry
  • Coherent interference effects in thin films
  • Incoherent limit available for thick substrates (future update)

Reference: Jimenez et al., SOl. Mat. 251, 112109 (2023), DOI: 10.1016/j.solmat.2022.112109

Electrical Model: Extended Detailed Balance

The device physics engine solves:

J(V) = Jph - J0_rad·[exp(qV/kT) - 1] 
       - J0_SRH·[exp(qV/nkT) - 1]
       - JAuger(V)
       - V/Rsh 
       - J·Rs

Key advantages:

  • No need to solve Poisson-drift-diffusion system
  • Faster iteration for design screening
  • Thermodynamic consistency checks
  • Direct link between optical and electrical models

Reference: Jehl Li-Kao, Solar RRL (2025), DOI: 10.1002/solr.202500345

Defect Modelling: Bulk and Interface Recombination

SOLEY translates microscopic trap parameters into macroscopic J₀ using the formulation from Scaffidi et al.:

Bulk recombination:
J₀₀_bulk = π·kB·T·√(ε·Nc·Nv/(2·q·Vbi·Ndop))·vth·σn·Nt

Interface recombination:
J₀₀_interface = q·Sp·Ndop·[(Nc_adj·Nv)/(Ndop_adj·Ndop)]^(1-θ)

Final J₀_SRH:
J₀_SRH = (J₀₀_bulk + J₀₀_interface)·exp(-Ea/(n·kB·T))

Reference: Scaffidi, R. et al. Newton 1(8), 100198 (2025). DOI: 10.1016/j.newton.2025.100198

Development Roadmap

Planned Features

Incoherent TMM

For thick substrates and glass layers

Enhanced EQE

Thermodynamic equations with improved collection probabilities

IBSC Physics

Intermediate band solar cells modelling

Hot Carrier Devices

Non-thermal carrier distributions

Known Limitations

  • Bruggeman mixing can cause layer indexing issues (use with caution)
  • Parallel processing overhead sometimes slower than serial for small datasets
  • macOS GUI scaling untested on all hardware variants
  • Limited built-in database of optical constants (users must provide n, k files)

Citation

If you use SOLEY in your research, please cite:

Jehl Li-Kao, Z. "SOLEY: a package for optical and extended detailed balance model for photovoltaic device simulation." Solar RRL (2025). DOI: 10.1002/solr.202500345

BibTeX

@article{jehl2025soley,
  author  = {Zacharie Jehl Li-Kao},
  title   = {SOLEY: a package for optical and extended 
             detailed balance model for photovoltaic 
             device simulation},
  journal = {Solar RRL},
  year    = {2025},
  doi     = {10.1002/solr.202500345}
}

License

SOLEY is distributed for academic use only. Commercial use requires explicit written permission from the author.

By downloading and using SOLEY, you agree to:

  • Use the software strictly for non-commercial research and educational purposes
  • Cite the software in any publications or presentations
  • Not redistribute modified versions without permission

Contact

Get in touch for questions, bug reports, feature requests, or collaboration opportunities.

📧 Email

zacharie.jehl@upc.edu

Use subject prefixes:
[SOLEY Bug] - Bug reports
[SOLEY Feature] - Feature requests
[SOLEY Collaboration] - Research collaboration

💼 LinkedIn

Connect on LinkedIn

Professional networking and updates

🐛 GitHub Issues

Report on GitHub

For bug tracking and feature discussions

Developer

Zacharie Jehl Li-Kao
Universitat Politècnica de Catalunya (UPC)
Barcelona, Spain