so on. We can add other absorption files for other relevant materials.
We can also change the model for absorption, model for recombination, and apply defects to a surface in addition to these basic parameters. A panel for layer properties snapshot is illustrated in Figure 1.5.
On the panel for cell definition, which opens the panel for the properties of contacts (Figure 1.5), you can configure the contact properties by either selecting the front or back contact button.
The identification of each contact is made as follows:
electron and hole surface recombination velocities,
information about the metal work function.
Figure 1.5 Layer properties panel in SCAPS.
After loading the solar cell design with the button for set problem on SCAPS, one can set the working point. The work point specifies the parameters in a measurement that are not varied:
Temperature, T: appropriate to all measurements. In SCAPS, the only variables that have an explicit dependence on temperature are NC(T), NV(T), and thermal voltage kBT.
Voltage, V: is discarded in simulation of I-V and C-V. It is the voltage for dc-bias in simulation of C-f and simulation of QE(λ). SCAPS starts at 0V and proceeds through a series of steps at the point of operation, which we can also define.
Frequency, f: is discarded in simulation of I-V, QE(λ) and C-f. It is the frequency of the simulation of the C-V measurement.
Illumination, the illumination requirements can be further defined when simulating under illumination. The main options are: dark or light, light side choice (left/right), spectrum option. A single sun(=1000 W/m3) illumination with the “air mass.5, global” spectrum is the default, but for specialized simulations, we have a wide range of monochromatic light and spectra.
In a diode, the current at n-contact is converted from the p-contact hole current to the electron current. It implies that recombination must occur somewhere in the diode, even in the most ideal device. The user must define recombination at least at one location (in a layer or interface) somewhere. Defects are most important parameters for study of solar cells. The following parameters identify defects in SCAPS:
position of energy level in the gap,
type of defect (i.e. acceptor, donor or neutral),
thermal capture cross-section for electrons,
thermal capture cross-section for holes,
energetic distribution (single, uniform …),
defect energy level reference (above EV or below EC),
optical cross section of electrons,
capture cross section of holes,
concentration of defects.
We can select one or more of the following measurements to be simulated in the action part of the action panel (Figure 1.3): I-V, C-V, C-f and QE(λ). The start and end values of the argument and the number of steps can be adjusted if necessary.
Figure 1.6 Screenshot of energy bands panel window in SCAPS.
We select the “calculate” button in the action panel after implementing all the necessary data (layer properties, solar cell configuration). The panel of the energy bands opens, and the calculations begin. The window for panel for energy bands opens after measurement with the band diagram, density of carriers, density of current, and probability of occupation of deep defects of graph plots of electrons as shown in Figure 1.6.
Then from the right side of the screen window of the energy bands one can select choices (Gen-Rec, I-V). The behavior of the solar cell like the short circuit current (JSC) may be derived from the I-V curve. The results can be saved for further editing or use in other programs as ASCII files (e.g., Excel). It is broadly used for the simulation and analysis of different types of solar cells [46–49].
1.7 Conclusion
From the study of these simulation softwares, it can be definitely said that simulation of perovskite solar cells can be used as a tool for designing and optimizing advanced perovskite solar cell structures and also to interpret the measurements made on different device structures. It can also be conclusively inferred that simulation can bring about better understanding of the detailed specifics of the working of perovskite solar cell structures. However, the simulation of perovskite solar cells requires a lot of input parameters, which makes it a tedious task.
All the softwares discussed here use Graphical User Interface except ASA, which uses ASCII file to input the values of various parameters. The number of layers that can be simulated is fixed in SCAPS and AMPS 1D, whereas there is no such fixation in AFORS-HET and ASA. All softwares studied use SRH recombination mechanism, whereas SCAPS and AMPS 1D also use band-to-band recombination. Auger recombination is considered in SCAPS. All the software studied here give the option to model defects. In SCAPS, up to seven defects can be simulated in any semiconductor layer, and all the parameters of each defect can be modified by “defect properties panel.” AMPS 1D allows Discrete and Banded Defect (Structural and Impurity) Levels and Generalized Defect (Structural and Impurity) Level Distributions. In AFORS-HET, defect distribution of states (DOS) has to be quantified for all layers and for the interfaces. In ASA, both the extended and localized states can be modeled using the defect-pool models. Modeling of tunnelling is available in all the softwares except AMPS 1D. All softwares are capable of doing electrical and spectral response measurements.
References
1. Neamen, D.A., Semiconductor physics and devices: basic principles, McGraw-Hill, New York, 2003.
2. Mandadapu, U., Vedanayakam, S.V., Thyagarajan, K., Babu, B.J., Optimisation of high efficiency tin halide perovskite solar cells using SCAPS-1D. Int. J. Simul. Process Model., 13, 3, 221–227, 2018.
3. Zeman, M., van den Heuvel, J., Pieters, B.E., Kroon, M., Willemen, J., Advanced semiconductor analysis, TU Delft, Delft, 2003.
4. Pieters, B.E., Krc, J., Zeman, M., May. Advanced numerical simulation tool for solar cells-ASA5, in: 2006 IEEE 4th World Conference on Photovoltaic Energy Conference, vol. 2, IEEE, pp. 1513–1516, 2006.
5. Pieters, BE., Zeman, M., Metselaar, JW., Extraction of the defect density of states of a-Si:H using Q-DLTS. In s.n. (Ed.), Proceedings of the STW annual workshop on semiconductor advances for future electronics and sensors (SAFE 2005), 38–42, STW, 2005.
6. Zeman, M., Willemen, J.A., Vosteen, L.L.A., Tao, G., Metselaar, J.W., Computer modelling of current matching in a-Si: H/a-Si: H tandem solar cells on textured TCO substrates. Sol. Energy Mater. Sol. Cells, 46, 2, 81–99, 1997.
7. Meier, J., Dubail, S., Fluckinger, R., Fisher, D., Keppner, H., Shah, A., Intrinsic microcrystalline silicon(μc-Si:H)—A promising new thin film solar cell material. In Proceedings of the 1st World Conference on Photovoltaic energy conversion,