Device Structure¶
This module contains the functions necessary to build a sample structure that can be read by the PDD solver. Typically, you will not need to use any of these except in the case of including quantum wells in the solar cell. In this case, you will need to use this methods to solve the quantum properties and create an effective medium before executing the PDD solver.
Main functions¶
- CreateDeviceStructure(name[, role='device', T=293, layers=[], comments='', repeat=1, substrate=DefaultMaterial, reflection=None])¶
Creates a dictionary with subdctionaries and lists storing all the parameters and material information necessary to solve the Poisson - Drift-Diffusion equations. It might be useful, also, to get all the properties of a given material that will be used in the PDD solver.
Layers is a list of objects of class solcore.Layer. A solcore.Structure or a solcore.Junction are also valid inputs since all of them are made of a list of layers. Any property not defined explicitly in the definition of the materials for the layers and that can not be calculated by
Solcoreis taken from the default material (see section Default material). substrate must be a solcore.material, otherwise the default material is used.Output: dictionary with all the information of the structure.
# This example illustrates the creation of a p-i-n Junction including AlGaAs window and back surface field layers.
# A custom absorption coefficient for the GaAs of the intrinsic layer is used.
import solcore.poisson_drift_diffusion as PDD
from solcore.structure import Layer, Junction
from solcore.import material
# First, we create the materials, overriding any default property we want, such as the doping or the absorption coefficient
window = material('AlGaAs') (T=300, Na = 1e24, Al=0.8)
p_GaAs = material('GaAs') (T=300, Na = 1e24)
i_GaAs = material('GaAs') (T=300)
n_GaAs = material('GaAs') (T=300, Nd = 1e23)
bsf = material('AlGaAs') (T=300, Nd = 1e24, Al=0.4)
# We put everything together in a Junction. We include the surface recombination velocities,
# sn and sp, although they are not necessary in this case.
MyJunction = Junction([ Layer(width = 30e-9, material = window, role="Window"),
Layer(width = 400e-9, material = p_GaAs, role="Emitter"),
Layer(width = 400e-9, material = i_GaAs, role="Intrinsic"),
Layer(width = 2000e-9, material = n_GaAs, role="Base"),
Layer(width = 200e-9, material = bsf, role="BSF")],
sn=1e3, sp=1e3, T=300, kind='PDD')
# Then, we create the structure. What actually this "creation" does is getting all the information of the materials
# from the materials database relevant for the PDD solver and storing them in a dictionary.
MyDevice = PDD.CreateDeviceStructure( 'TestDevice', T = MyJunction.T, layers = MyJunction)
Now “MyDevice” is a dictionary with several entries with the specific information that will be used by the PDD solver (if required). For example MyDevice['layers'][1]['properties'] will contain the following (the order might be different):
{'composition': {'material': 'GaAs'},
'width': 4e-07,
'band_gap': 2.279067404056071e-19,
'electron_affinity': 6.62903371354393e-19,
'eff_mass_electron_Gamma': 0.067,
'eff_mass_hh_z': 0.34129421032745344,
'eff_mass_lh_z': 0.0879370668050916,
'electron_mobility': 0.9399999990563772,
'hole_mobility': 0.017374281562790292,
'ni': 1767480124457.733,
'Nc': 4.3519622483962564e+23,
'Nv': 5.657793654818883e+24,
'electron_minority_lifetime': 3e-06,
'hole_minority_lifetime': 2.5e-07,
'permittivity': 12.9,
'electron_auger_recombination': 1e-42,
'hole_auger_recombination': 1e-42,
'radiative_recombination': 2.8744203894058427e-17,
'Nd': 1, 'Na': 1e+24,
'sn': 1000000.0,
'sp': 1000000.0}
The information for layers 2 and 3 wil be similar since we have GaAs in all cases, except for the mobilities as these depend on the doping, which is different.
Default material¶
The default material is GaAs at 293K. In general, all the intrinsic properties of the materials are taken from the literature and calculated by the Solcore material system. If not found there (for example if the material or alloy is not in the database) or if they are extrinsic, the default values below are used. The extrinsic properties, that depend on the quality of the material or its doping, are just asigned a ‘reasonable’ value. The user must make sure that this ‘reasonable’ value is indeed resonable for the intended application and override it with his/her own, otherwise.
The total list of parameters and the default values are:
Parameter |
Default value |
Units |
Notes |
|---|---|---|---|
band_gap |
Calculated for GaAs at 293K |
J |
- |
electron_affinity |
Calculated for GaAs at 293K |
J |
- |
eff_mass_electron_Gamma |
Calculated for GaAs at 293K |
relative to m0 |
- |
eff_mass_hh_z |
Calculated for GaAs at 293K |
relative to m0 |
- |
eff_mass_lh_z |
Calculated for GaAs at 293K |
relative to m0 |
- |
permittivity |
12.9 |
relative to epsilon0 |
- |
electron_mobility |
Calculated for GaAs at 293K |
m2 V-1 s-1 |
- |
hole_mobility |
Calculated for GaAs at 293K |
m2 V-1 s-1 |
- |
electron_minority_lifetime |
3e-6 |
s |
SRH [1] recombination time for electrons |
hole_minority_lifetime |
2.5e-7 |
s |
SRH recombination time for holes |
electron_auger_recombination |
1e-42 |
m6 s-1 |
- |
hole_auger_recombination |
1e-42 |
m6 s-1 |
- |
radiative_recombination |
Calculated for GaAs |
m3 s-1 |
Derived from the absorption coefficient |
Nd |
1 |
m-3 |
Density of donors |
Na |
1 |
m-3 |
Density of acceptors |