5.2.2 Layer specific parameters

The parameters that define the properties of a layer such as generation, recombination, mobilities, trapping and ions. Each layer has its own file and the structure of the file is the same for each layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} version}}\)
The code verifies that the version number of the parameter file matches that of the program. If not, it exits.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} L}}\)
Thickness (m) of the layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} eps\_ r}}\)
Relative dielectric constant.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ c}}\)
Conduction band edge (eV, positive).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ v}}\)
Valence band edge (eV, positive).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ c}}\)
Effective density of states (m\(^{-3}\)) of the conduction and valence bands.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ D}}\)
Ionised n-doping (m\(^{-3}\)).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ A}}\)
Ionised p-doping (m\(^{-3}\)).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ n}}\)
Electron mobility (m\(^2\)/Vs) at zero field.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ p}}\)
Hole mobility (m\(^2\)/Vs) at zero field.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mobnDep}}\)
This integer value (0 or 1) specifies whether the electron mobility is constant (0) or is field-dependent (1). The field-dependence is of the form

\begin{equation} \mu (F) = \mu _{n} \exp \left(\gamma \sqrt{F}\right), \end{equation}
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where \(\mu _{n}\) is the zero-field mobility (\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ n}}\)), \(F\) is the absolute electric field, and \(\gamma \) is the field activation factor for electrons \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} gamma\_ n}}\).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mobpDep}}\)
This integer value (0 or 1) specifies whether the hole mobility is constant (0) or is field-dependent (1). The field-dependence is of the form

\begin{equation} \mu (F) = \mu _{p} \exp \left(\gamma \sqrt{F}\right), \end{equation}
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where \(\mu _{p}\) is the zero-field mobility (\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ p}}\)), \(F\) is the absolute electric field, and \(\gamma \) is the field activation factor for holes \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} gamma\_ p}}\).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} gamma\_ n}}\)
Field-activation factor (\(\sqrt{\rm m/V}\)) of the electron mobility. Only relevant if \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mobnDep}}\) is set to 1.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} gamma\_ p}}\)
Field-activation factor (\(\sqrt{\rm m/V}\)) of the hole mobility. This is only relevant if \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mobpDep}}\) is set to 1.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ n}}\)
Interface transfer velocity (m/s) of electrons to layer to the right. Internally, \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ n}}\) is converted to a mobility \(\mu _{\rm int}\) at the interface such that the current-voltage curve does not depend on the grid spacing:

\begin{equation} \mu _{\rm int}=(q/kT) \Delta x \mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ n}}~ , \end{equation}
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where \(\Delta x\) is the (local) grid spacing. See section 2.3 for details.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ p}}\)
Interface transfer velocity (m/s) of holes to layer to the right. Internally, \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ p}}\) is converted to a mobility \(\mu _{\rm int}\) at the interface such that the current-voltage curve does not depend on the grid spacing:

\begin{equation} \mu _{\rm int}=(q/kT) \Delta x \mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nu\_ int\_ p}}~ , \end{equation}
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where \(\Delta x\) is the (local) grid spacing. See section 2.3 for details.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ t\_ int}}\)
Number of traps per area (m\(^-2\)) at the interface with the layer to the right.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ int}}\)
Energy level (relative to vacuum, eV) of traps at the interface with the layer to the right.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} intTrapFile}}\)
This specifies the name of the file that is used to specify multiple interface trap levels, see section 3.3 for details). Using such a file means that \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ int}}\) is ignored for traps at the interface with the layer to the right. If set to ‘none’, then this file is not read and the trap level (if any) is taken from \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ int}}\).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} intTrapType}}\)
Integer value (-1, 0, 1) to specify the type of trap at the interface with the layer to the right: -1: acceptor, 0: neutral, 1: donor.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} C\_ n\_ int}}\)
Capture coefficient (m\(^3\) s\(^{-1}\)) for electrons for traps at the interface with the layer to the right. Set to 0 in order to exclude capture from and emission to the conduction band.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} C\_ p\_ int}}\)
Capture coefficient (m\(^3\) s\(^{-1}\)) for holes for traps at the interface with the layer to the right. Set to 0 in order to exclude capture from and emission to the valence band.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ anion}}\)
Concentration of negative ions (m\(^{-3}\)). Note, it does not matter whether these are ions, dopants, or vacancies. It is simply a singly negatively charged species that may move or not.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ cation}}\)
Concentration of positive ions (m\(^{-3}\)). Note, it does not matter whether these are ions, dopants, or vacancies. It is simply a singly positively charged species that may move or not.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ anion}}\)
Mobility of negative ions (m\(^{-2}\)/Vs). Take 0 if they are not supposed to move, this will result in a uniform profile for this layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} mu\_ cation}}\)
Mobility of positive ions (m\(^{-2}\)/Vs). Take 0 if they are not supposed to move, this will result in a uniform profile for this layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} ionsMayEnter}}\)
Integer value to indicate whether ions can enter from other layers (yes=1, no\(\neq \)1).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} G\_ ehp}}\)
The generation rate (m\(^{-3}\) s\(^{-1}\)) of electron-hole pairs in this layer. Only used if there is no generation profile (either supplied by the user or calculated using the transfer matrix algorithm). Parameter \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} G\_ frac}}\) rescales this value. Note: the generation rate of free electrons and holes can be smaller than this if the Onsager-Braun model is employed. When the value of the generation rate is defined in the generation profile, set to 1.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} layerGen}}\)
Integer value to indicate whether this layer absorbs / generates electron-hole pairs (yes=1, no\(\neq \)1). This overrides a user-defined or calculated generation profile in case this is specified (as defined by parameter \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} genProfile}}\)).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} nkLayer}}\)
Name of file with n,k values of this layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} fieldDepG}}\)
Integer value to indicate whether field-dependent splitting of electron-hole pairs should be used (yes=0, no\(\neq \)1). See section 2.5.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} P0}}\)
Fraction of electron-hole pairs that directly yield free charge carriers. Only relevant if the Onsager-Braun model of charge generation is used. See section 2.5.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}\)
Charge separation distance (m) in the Onsager-Braun model.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} thermLengDist}}\)
Integer value that selects which distribution of thermalisation lengths should be used in the Onsager-Braun model. (1) specifies a delta function, the other distributions are:
2: Gaussian

\begin{equation} g(a,r)=\frac{4}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ ^3 \sqrt{\pi }} r^2 \exp \left[-\left(\frac{r}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ }\right)^2\right] \end{equation}
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3: Exponential

\begin{equation} g(a,r)=\frac{1}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ }\exp \left[-\frac{r}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ }\right] \end{equation}
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4: \(r^2\) exponential

\begin{equation} g(a,r)=\frac{r^2}{2\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ ^3}\exp \left[-\frac{r}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ }\right] \end{equation}
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5: \(r^4\) Gaussian

\begin{equation} g(a,r)=\frac{8r^4}{3\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ ^5 \sqrt{\pi }} r^2 \exp \left[-\left(\frac{r}{\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} a}}~ }\right)^2\right]. \end{equation}
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\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} k\_ f}}\)
Decay rate (1/s) of charge-transfer states as used in the Onsager-Braun model. [ 12 , 13 , 14 ]

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} k\_ direct}}\)
Rate constant (m\(^3\)/s) of direct (band-to-band, or bimolecular) recombination.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} preLangevin}}\)
Prefactor of the Langevin expression, should be positive but not larger than 1.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} useLangevin}}\)
Integer value to specify whether the rate constant of direct recombination is calculated from the Langevin expression (1) or not (\(\neq \)1). In the former case, \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} preLangevin}}\) is used in conjunction with the Langevin expression. In the latter, \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} k\_ direct}}\) is used.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} N\_ t\_ bulk}}\)
Defines the density (m\(^{-3}\)) of traps in the bulk of the layer.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ bulk}}\)
Energy level (relative to vacuum, eV) of traps in the bulk.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} bulkTrapFile}}\)
This specifies the name of the file that is used to specify multiple bulk trap levels, see section 3.3 for details). Using such a file means that \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ bulk}}\) is ignored for bulk traps. If set to ‘none’, then this file is not read and the trap level (if any) is taken from \(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} E\_ t\_ bulk}}\).

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} bulkTrapType}}\)
Integer value (-1, 0, 1) to specify the type of bulk trap: -1: acceptor, 0: neutral, 1: donor.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} C\_ n\_ bulk}}\)
Capture coefficient (m\(^3\) s\(^{-1}\)) for electrons for traps in the bulk. Set to 0 in order to exclude capture from and emission to the valence band.

\(\mathtt{\require{color}{\color[rgb]{0.000000000000000,0.500000000000000,0.500000000000000} C\_ p\_ bulk}}\)
Capture coefficient (m\(^3\) s\(^{-1}\)) for holes for traps in the bulk. Set to 0 in order to exclude capture from and emission to the valence band.