Merge pull request #134 from qpv-research-group/rwca_in_tests

Rwca in tests

.github/workflows/test_unit_and_examples.yml

@@ -30,7 +30,7 @@ jobs:
 
     - name: Install system dependencies in Linux
       if: matrix.os == 'ubuntu-latest'
-      run: sudo apt install -y gfortran ngspice
+      run: sudo apt install -y gfortran ngspice python3-tk libboost-all-dev libopenblas-dev libfftw3-dev libsuitesparse-dev
 
     - name: Install system dependencies in MacOS
       if: matrix.os == 'macos-latest'
@@ -45,6 +45,16 @@ jobs:
         python -m pip install --upgrade setuptools wheel pip twine numpy
         python -m pip install -e .[dev]
 
+    - name: Install S4 in Linux
+      if: matrix.os == 'ubuntu-latest'
+      run: |
+        git clone https://github.com/phoebe-p/S4
+        cd S4
+        #make boost
+        make S4_pyext
+        cd ..
+        rm -rf S4
+
     - name: Install Solcore Linux and MacOS
       if: matrix.os != 'windows-latest'
       run: python -m  pip install --no-deps --force-reinstall --install-option="--with_pdd" -e .

docs/source/Examples/example_optics_comparison.rst

@@ -0,0 +1,130 @@
+Comparison of Solcore's optical models
+======================================================================
+
+.. image:: optmodelcomp.png
+   :width: 80%
+
+The different optical models in Solcore are suitable for different purposes. The Beer-Lambert (BL) model does not include front surface reflection,
+unless it is externally specified, but is extremely fast and may be suitable for material stacks where the layers are optically thick
+(especially if the front surface reflectivity is specified by the user, e.g. from measured data). The transfer matrix model (TMM)
+deals with multi-layer interference correctly, and can be used at multiple incidence angles and either s, p, or unpolarized light.
+Finally, the RCWA capability integrated in Solcore is the most advanced solver, capable of dealing with periodic structures.
+For any multi-layer structures without diffracting layers, it gives the same results as the TMM solver. However, as the number
+of diffraction orders used in the calculation increases, the computation time can become very significant.
+
+The plot above shows the EQE results for a thin GaAs cell with various light-trapping structures, considered using
+the different solvers. The structure is a relatively thin (500 nm) GaAs cell, with :math:`TiO_2` nanoparticles (NPs) on the front
+and a distributed Bragg reflector (DBR) consisting of 10 GaAs/AlAs bilayers. The NP array is made up of disks 50 nm in height,
+with 100 nm diameter and arranged in a square pattern with a period of 400 nm. A DBR is a selective reflector, in this case
+designed to reflect light with wavelengths around 800 nm, close to the bandgap of GaAs where transmission losses would be highest.
+The figure above shows that the simplest model, the BL law, does not give any front-surface reflection, with all the light absorbed
+at short wavelengths. At longer wavelengths, there is some transmission into the GaAs substrate; although absorption in the DBR
+will be calculated, the interference effects which lead to wavelength-selective reflection are ignored by the BL model.
+The TMM model with the DBR removed from the structure shows a similar profile to the BL EQE, but significantly lower due
+to reflection at the front surface. When the DBR is included, two clear new peaks in the EQE calculated using the TMM are
+observed. Finally, when the full structure is modelled using RCWA, these peaks due to the DBR remain but the EQE at all
+wavelengths is increased, due to an anti-reflection effect from the NPs and increased path length in the GaAs cell
+due to diffraction effects.
+
+
+.. code-block:: Python
+
+    import numpy as np
+    import matplotlib.pyplot as plt
+
+    from solcore import si, material
+    from solcore.structure import Junction, Layer
+    from solcore.solar_cell import SolarCell
+    from solcore.solar_cell_solver import solar_cell_solver, default_options
+    from solcore.light_source import LightSource
+    from solcore.constants import vacuum_permittivity
+    from solcore.optics import RCWASolverError
+
+    # user options
+    T = 298
+    wl = si(np.linspace(400, 900, 80), 'nm')
+    light_source = LightSource(source_type='standard', version='AM1.5g', x=wl,
+                               output_units='photon_flux_per_m', concentration=1)
+    opts = default_options
+    opts.wavelength, opts.no_back_reflection, opts.size, opts.light_source, opts.T_ambient = \
+        wl, False, ((400, 0), (0, 400)), light_source, T
+    opts.recalculate_absorption = True
+    # The size of the unit cell for the RCWA structure is 400 x 400 nm
+
+    # Defining all the materials we need
+    Air = material('Air')(T=T)
+    p_GaAs = material('GaAs')(T=T, Na=si('4e18cm-3'))  # for the GaAs cell emitter
+    n_GaAs = material('GaAs')(T=T, Nd=si('2e17cm-3'))  # for the GaAs cell base
+    AlAs, GaAs = material('AlAs')(T=T), material('GaAs')(T=T)  # for the DBR
+    SiO2 = material('SiO2', sopra=True)(T=T)  # for the spacer layer
+    TiO2 = material('TiO2', sopra=True)(T=T)  # for the nanoparticles
+
+    # some parameters for the QE solver
+    for mat in [n_GaAs, p_GaAs]:
+        mat.hole_mobility, mat.electron_mobility, mat.permittivity = 3.4e-3, 5e-2, 9 * vacuum_permittivity
+        n_GaAs.hole_diffusion_length, p_GaAs.electron_diffusion_length = si("500nm"), si("5um")
+
+    # Define the different parts of the structure we will use. For the GaAs junction, we use the depletion approximation
+    GaAs_junction = [Junction([Layer(width=si('100nm'), material=p_GaAs, role="emitter"),
+                               Layer(width=si('400nm'), material=n_GaAs, role="base")], T=T, kind='DA')]
+
+    # this creates 10 repetitions of the AlAs and GaAs layers, to make the DBR structure
+    DBR = 10 * [Layer(width=si("73nm"), material=AlAs), Layer(width=si("60nm"), material=GaAs)]
+
+    # The layer with nanoparticles
+    NP_layer = [Layer(si('50nm'), Air, geometry=[{'type': 'circle', 'mat': TiO2, 'center': (200, 200),
+                                                  'radius': 50}])]
+
+    substrate = [Layer(width=si('50um'), material=GaAs)]
+    spacer = [Layer(width=si('25nm'), material=SiO2)]
+
+    # --------------------------------------------------------------------------
+    # solar cell with SiO2 coating
+    solar_cell = SolarCell(spacer + GaAs_junction + substrate)
+
+    opts.optics_method = 'TMM'
+    solar_cell_solver(solar_cell, 'qe', opts)
+    TMM_EQE = solar_cell[1].eqe(opts.wavelength)
+
+    opts.optics_method = 'BL'
+    solar_cell_solver(solar_cell, 'qe', opts)
+    BL_EQE = solar_cell[1].eqe(opts.wavelength)
+
+    # --------------------------------------------------------------------------
+    # as above, with a DBR on the back
+    solar_cell = SolarCell(spacer + GaAs_junction + DBR + substrate)
+
+    opts.optics_method = 'TMM'
+    solar_cell_solver(solar_cell, 'qe', opts)
+    TMM_EQE_DBR = solar_cell[1].eqe(opts.wavelength)
+
+    # --------------------------------------------------------------------------
+    # cell with TiO2 nanocylinder array on the front
+    solar_cell = SolarCell(NP_layer + spacer + GaAs_junction + DBR + substrate)
+
+    opts.optics_method = 'TMM'
+    solar_cell_solver(solar_cell, 'qe', opts)
+    TMM_EQE_NP = solar_cell[2].eqe(opts.wavelength)
+
+    opts.optics_method = 'BL'
+    solar_cell_solver(solar_cell, 'qe', opts)
+    BL_EQE_NP = solar_cell[2].eqe(opts.wavelength)
+
+    try:
+        opts.optics_method = 'RCWA'
+        opts.orders = 19  # number of diffraction orders to keep in the RCWA solver
+        solar_cell_solver(solar_cell, 'qe', opts)
+        RCWA_EQE_NP = solar_cell[2].eqe(opts.wavelength)
+        RCWA_legend = 'RCWA (GaAs SC + NP array + DBR)'
+    except RCWASolverError:
+        RCWA_EQE_NP = np.zeros_like(BL_EQE_NP)
+        RCWA_legend = '(RCWA solver S4 not available)'
+
+
+    plt.figure()
+    plt.plot(wl * 1e9, BL_EQE_NP, wl * 1e9, TMM_EQE, wl * 1e9, TMM_EQE_DBR, wl * 1e9, RCWA_EQE_NP)
+    plt.legend(labels=['Beer-Lambert law (all structures)', 'TMM (GaAs SC)', 'TMM (GaAs SC + DBR)',
+                       RCWA_legend])
+    plt.xlabel("Wavelength (nm)")
+    plt.ylabel("Quantum efficiency")
+    plt.show()

docs/source/Examples/main.rst

@@ -18,8 +18,8 @@ Optical methods
 ---------------
 
 - :doc:`Using the TMM solver to calculate the reflextion of a multilayered ARC <example_RAT_of_ARC>`
-- :doc:`Looking at the effect of substrate and the no_back_reflection option in the TMM solver <substrate_example>`
-- :doc:`Coherent and incoherent layers in the TMM solver<example_coherency>`
+- :doc:`Looking at the effect of substrate and the no_back_reflection option in the TMM solver <example_substrate>`
+- :doc:`Comparing optical models (TMM, Beer-Lambert, and RCWA) <example_optics_comparison>`
 
 Custom materials
 ----------------