Perovskite Materials for Energy and Environmental Applications. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119763352
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on the DC voltage of the cell. The device conductance G(ω)/capacitance C(ω) at the specified frequency ω may be determined from the real/imaginary parts of the AC cell current:

image

      When conducted under open-circuit situations, the impedance of a ZnO/a-Si:H(n)/c-Si(p)/Al heterojunction silicon solar cell is quite susceptible to the interface state density Dit. For larger Dit, 1010 cm−2≤ Dit ≤ 1012 cm−2, the resonant frequency (maximum of the phase shift) shifts toward higher frequencies. On the other hand, if operated under dark or short-circuit conditions, the Dit sensitivity is low: for instance, the conductance depending on the temperature in the dark changes only for Dit≥1012 cm−2 which is related to a change of the band bending at the equilibrium.

      If ZnO/a-Si:H(n)/c-Si(p)/Al silicon heterojunction solar cells are excited by a monochromatic laser pulse at a wavelength of 900 nm, the generation of extra carriers occurs only in the c-Si(p) wafer. Hence, the recombination of the a-Si:H/c-Si interface may be efficiently tested. The SPV signal essentially tracks the shift in band bending at the surface because of excessive generation/recombination of carrier, whereas the PL signal is straight linked to excess generation/recombination of carrier. When laser pulse of 10 ns is used, all signals during the pulse do not enter conditions of steady state. Nevertheless, the two signals’ degeneration behavior occur in different time domains. It is inside the range of ms for decay of SPV and within the range of 100 ns for decay of PL. The density of states at a-Si:H/c-Si interface, Dit critically relies not only on the early values immediately after the pulse but also on the transient decay.

      Until now, the AFORS-HET software has been primarily used to (1) determine total achievable amorphous/crystalline solar cells efficiencies, (2) create criteria for designing for such solar cells, (3) establish calculation approaches for controlling a-Si:H/c-Si recombination interface.

      SCAPS is a one-dimensional program for simulation of solar cells established at the University of Ghent’s Department of Electronics and Information Systems (ELIS). It analyzes the behavior and characteristics of solar cell structures numerically. Various measurements of the output parameters of solar cells could be performed by SCAPS. It can calculate the open circuit voltage (Voc), the short circuit current (Jsc), the output characteristic J-V, the fill factor (FF), the quantum efficiency (QE), the output efficiency of the cell, the generation and recombination profiles, and so on [27–30].

      The electrical characteristics can be determined according to the defined physical structure and conditions of bias. This can be done by the assumption that the device’s function can be approximated into a grid in one dimension composed of a set of grid points also called as nodes. The transport of carriers through the system can be modeled by adding the set of differential equations (Poisson’s equation and continuity equations) on this grid (or the discretization of the equation). The grid with finite element can be used to depict the domain of the simulation.

      SCAPS is a program for Windows, and some of its chief characteristics are classified here as follows:

       It is possible to include up to seven layers of semiconductor to the solar cell device.

       When required, gradation of nearly all physical parameters can be done in a new window.

       Capacity to approximate band diagram in steady state, profile for recombination, and transport of carrier.

       Variable bias of voltage, different temperature, and various illumination options

       Can be used to measure concentrations and currents, J-V, C-f, C-V, and Q-V, AC characteristics and spectral response.

       Calculation of single and batch values.

       Final, as well as intermediate values, graphs, and other significant data, can be obtained as output and can be exported

       thickness (μm),

       electron affinity (eV),

       band gap (eV),

       dielectric permittivity (relative),

       valance band effective density of states (1/cm3),

       conduction band effective density of states (1/cm3),

       hole thermal velocity (cm/s),

       electron thermal velocity (cm/s),

       acceptor shallow density (ND),

       donor shallow density (ND).

Snapshot of the action panel of SCAPS. Snapshot of the solar cell definition panel of SCAPS.

      The optical absorption of the semiconductor layers can be taken from a user file. Examples of such user files are distributed with the program: Si.abs,