of Perovskite Based Solar Cells(metal-halide)
Swati kandoria , Saket kumar
and communication engineering department
institute of technical teacher training and research
Abstract- Perovskite based solar cells have attracted much recent research
interest due to the large efficiencies reported for simple planar structures.
However, there is a lack of clarity in literature on the key functional
parameters that control the eventual efficiencies. In this article, we provide
a comprehensive modeling framework, well calibrated with experimental results
from literature, to understand/interpret Perovskite based solar cells and
suggest further optimization schemes. Indeed, our results show that the dark
and light characteristics of these devices are dominated by recombination in
Perovskite layer. Curiously, our analytical model predicts that the open
circuit voltage could be much larger than built-in potential, a result
supported by both literature results and numerical simulations. Finally, we
identify optimization pathways to achieve >20% efficiency for such solar
Index Terms – Perovskite
solar cell, features , material, architecture, model system, trade-off,
efficiency, ETL/HTL properties, conclusion, acknowledgement
A sun based cell, or photovoltaic cell (beforehand named
“sun powered battery”), is an electrical gadget that changes over the
vitality of light specifically into power by the photovoltaic impact, which is
a physical and concoction marvel. It is a type of photoelectric cell,
characterized as a gadget whose electrical qualities, for example, current, voltage,
or protection, shift when presented to light.
Sun powered cells are the building pieces of photovoltaic
modules, also called sun oriented boards.Sun based cells are portrayed as being
photovoltaic, independent of whether the source is daylight or a counterfeit
light. They are utilized as a photodetector.
The operation of a photovoltaic (PV) cell requires three
The retention of light, generating either electron-gap sets
or excitons.The partition of charge transporters of inverse kinds.
The different extraction of those bearers to an outer
Interestingly, a sun powered warm gatherer supplies warm by
retaining daylight, with the end goal of either coordinate warming or aberrant
electrical power age from warm.
One of the solar cell
type is perovskite solar cell,
solar cell is a type of solar cell which
includes a perovskite
structured compound, most commonly a hybrid
organic-inorganic lead or tin
halide-based material, as the
light-harvesting active layer. Perovskite materials such as methylammonium lead halides are cheap to produce and simple to manufacture.
I (a) shows a schematic of a Perovskite based solar cell. It consists of three
materials sandwiched between two electrodes – front contact (FC) and back
contact (BC). The middle layer is a Perovskite compound that absorbs solar
radiation resulting in generation of electron-hole pairs. The Electron
Transport Layer (ETL) and Hole Transport Layer (HTL) allow selective collection
of charge carriers at their respective electrodes. Although Perovskites form a
part of general class of materials having crystal structure as that of calcium
titanium oxide (CaTi03), the compounds reported for solar cell applications
mostly consist of organo-metallic halides 1-4. Researchers have tried with
various types of Perovskites by changing the halide group 4-6 and large
carrier diffusion lengths are also reported 7. This allows one to use thicker
absorber material such that almost all solar radiation beyond band gap energy
can be absorbed thus resulting in high short circuit current density 1.
dark and light current of Perovskite cells are dominated by recombination in
absorber region, (b) Voc of the cells depends on the carrier lifetime in
Perovskites and could be much greater than the built-in potential, Vbi, (c)
carrier mobility in ETL and HTL mostly affect the fill factor, FF, while (d) lT
product of Perovskite significantly affects both Jsc and FF. Based on our
simulation results, we also prescribe optimization routes to achieve> 20%
efficiency for Perovskite based solar cells.
halide perovskites possess unique features that make them exciting for solar
cell applications. The raw materials used, and the possible fabrication methods
(such as various printing techniques) are both low cost. Their high
absorption coefficient enables ultrathin films of around 500 nm to absorb
the complete visible solar spectrum. These features combined result in the
possibility to create low cost, high efficiency, thin, lightweight and flexible
The name ‘perovskite solar
cell’ is derived from the ABX3 crystal structure of the absorber materials, which is referred to as perovskite structure. The most commonly studied
perovskite absorber is methylammonium lead trihalide (CH3NH3PbX3,
where X is a halogen atom such as iodine, bromine or chlorine), with an optical bandgap between 1.5 and 2.3 eV depending on halide
content. Formamidinum lead trihalide (H2NCHNH2PbX3)
has also shown promise, with bandgaps between 1.5 and 2.2 eV. The minimum
bandgap is closer to the optimal for a single-junction cell than methylammonium lead
trihalide, so it should be capable of higher efficiencies.14 The first use of perovskite in a solid state solar cell was in a
dye-sensitized cell using CsSnI3 as a p-type hole transport
layer and absorber.15 A common concern is the inclusion of lead as a component of the
perovskite materials; solar cells based on tin-based
perovskite absorbers such as CH3NH3SnI3 have
also been reported with lower power-conversion efficiencies.
ARCHITECTURES OF PEROVSKSITE SOLAR CELLS AND
Three types of perovskite solar cells are designed to
simulate the effects of architectures and material properties on the device
performance. A HTM-free perovskite solar cell is given in Fig. 1(a). The solar
cell with a perovskite layer sandwiched between ZnO and CuSCN is shown in Fig.
1(b). The perovskite solar cell with double light absorbers is firstly designed
in Fig. 1(c). Fig. 1(d) shows the energy level diagram of each layer in these
devices. SCAPS was developed based on first-principle continuity and Poisson’s
equations (see supplemental material for more details). The computer program
was well adapted to simulating transport physics in solid state devices, such
as homojunction, heterojunction, and multijunction, and formulated to analyze,
design, and optimize structures intended for microelectronic, photovoltaic, or
opto-electronic applications 27. Material parameters set for device simulation
are carefully selected from those reported experimental. The UV-visible
absorption spectrum of MAPbI3 and MAPbBr3 were measured to be used as a
starting point for the optimization of the device structure.
device characteristics under dark and illuminated conditions are simulated
through self-consistent solutions of drift-diffusion and Poisson’s equations
8. Various material parameters and band level alignments used in this study
are shown in Fig. 1 (b). Here, ETL (225 nm thick) properties closely match that
of Ti02 9 while the HTL (200 nm thick) properties are adapted from
spiro-MeOTAD lO. We assume uniform photo-generation of carriers in
Perovskite- a valid assumption as the reported carrier diffusion lengths (>l/Jm,7)
in the Perovskite is much larger than the absorber thickness (300 nm). The
generation rate is normalized such that the entire solar spectrwn beyond the
Perovskite band gap (assumed as l.55 eV) 2 is absorbed. We also assume SRH as
the dominant carrier recombination mechanism in Perovskite while ETL and HTLare
treated recombination/generation free. Electrode work functions are asswned to
be 4.2 eV and 5.1 eV for front and back electrode, respectively.
excellent match between literature results and our simulations(Fig. 2) indicate
that our modeling methodology is well calibrated and the parameters used are
appropriate. With this as the bench mark, we now identify the critical
functional parameters that dictate eventual performance. A. Role of carrier
lifetime on Voc
3 (a) indicates that electron and hole concentrations are uniform for most part
of absorber under Voc conditions. Equating the photo-generation (rate G) to
carrier recombination (SRH mechanism), we find that the open circuit voltage as
given by V DC = 2 x 1n(2GrI n) (1) Fig. 3 (b) shows the simulated light I-V
characteristics as a function of carrier lifetime , and /J, while /J’ is held a
constant. The inset of part (b) shows that eq. (1) closely predicts the
simulated Voc results, and is independent of /J.
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