7 research outputs found
CsPbIBr<sub>2</sub> Perovskite Solar Cell by Spray-Assisted Deposition
In this work, an
inorganic halide perovskite solar cell using a
spray-assisted solution-processed CsPbIBr<sub>2</sub> film is demonstrated.
The process allows sequential solution processing of the CsPbIBr<sub>2</sub> film, overcoming the solubility problem of the bromide ion
in the precursor solution that would otherwise occur in a single-step
solution process. The spraying of CsI in air is demonstrated to be
successful, and the annealing of the CsPbIBr<sub>2</sub> film in air
is also successful in producing a CsPbIBr<sub>2</sub> film with an
optical band gap of 2.05 eV and is thermally stable at 300 °C.
The effects of the substrate temperature during spraying and the annealing
temperature on film quality and device performance are studied. The
substrate temperature during spraying is found to be the most critical
parameter. The best-performing device fabricated using these conditions
achieves a stabilized conversion efficiency of 6.3% with negligible
hysteresis. Cesium metal halide perovskites remain viable alternatives
to organic metal halide perovskites as the cesium-containing perovskites
can withstand higher temperature
Strontium-Doped Low-Temperature-Processed CsPbI<sub>2</sub>Br Perovskite Solar Cells
Cesium
(Cs) metal halide perovskites for photovoltaics have gained
research interest due to their better thermal stability compared to
their organic–inorganic counterparts. However, demonstration
of highly efficient Cs-based perovskite solar cells requires high
annealing temperature, which limits their use in multijunction devices.
In this work, low-temperature-processed cesium lead (Pb) halide perovskite
solar cells are demonstrated. We have also successfully incorporated
the less toxic strontium (Sr) at a low concentration that partially
substitutes Pb in CsPb<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>I<sub>2</sub>Br. The crystallinity, morphology,
absorption, photoluminescence, and elemental composition of this low-temperature-processed
CsPb<sub>1–<i>x</i></sub>Sr<sub><i>x</i></sub>I<sub>2</sub>Br are studied. It is found that the surface of
the perovskite film is enriched with Sr, providing a passivating effect.
At the optimal concentration (<i>x</i> = 0.02), a mesoscopic
perovskite solar cell using CsPb<sub>0.98</sub>Sr<sub>0.02</sub>I<sub>2</sub>Br achieves a stabilized efficiency at 10.8%. This work shows
the potential of inorganic perovskite, stimulating further development
of this material
Water-Free, Conductive Hole Transport Layer for Reproducible Perovskite–Perovskite Tandems with Record Fill Factor
State-of-the-art perovskite–perovskite tandem
solar cells
incorporate a water-based poly(3,4-ethylenedioxythiophene):polystyrenesulfonate
(PEDOT:PSS) hole transport layer in its low bandgap subcell. However,
there is a limitation regarding its use due to the moisture sensitivity
of perovskites and the insulating property of PSS. Here, we overcome
the limitation by using a water-free and PSS-free PEDOT-based hole
transport layer for low bandgap single-junction perovskite solar cells
and in perovskite–perovskite tandems. The champion tandem cell
produces an efficiency of 21.5% and a fill factor of 85.8%, the highest
for any perovskite-based double-junction tandems. Results of photoelectron
spectroscopy, Fourier-transform infrared spectroscopy, and conductive
atomic force microscopy reveal evidence of enhanced conductivity of
water-free and PSS-free PEDOT compared to its conventional counterpart.
The use of water-free and PSS-free PEDOT also eliminates decomposition
of high bandgap subcell with its interfacing layer stack in a tandem
that otherwise occurs with conventional PEDOT:PSS. This leads to enhanced
reproducibility of perovskite–perovskite tandems
High-Efficiency Rubidium-Incorporated Perovskite Solar Cells by Gas Quenching
We
apply gas quenching to fabricate rubidium (Rb) incorporated
perovskite films for high-efficiency perovskite solar cells achieving
20% power conversion efficiency on a 65 mm<sup>2</sup> device. Both
double-cation and triple-cation perovskites containing a combination
of methylammonium, formamidinium, cesium, and Rb have been investigated.
It is found that Rb is not fully embedded in the perovskite lattice.
However, a small incorporation of Rb leads to an improvement in the
photovoltaic performance of the corresponding devices for both double-cation
and triple-cation perovskite systems
The Effect of Stoichiometry on the Stability of Inorganic Cesium Lead Mixed-Halide Perovskites Solar Cells
Metal halide perovskite
solar cells that use the inorganic cation
Cs have been shown to have better thermal stability than the organic
cation containing counterparts, and CsPbI<sub>2</sub>Br has a more
suitable (lower) band gap than CsPbIBr<sub>2</sub> as a photovoltaic
energy harvesting material. However, increase in iodine content reduces
structural stability due to the preference toward the non-perovskite
orthorhombic phase when the film is exposed to air. In this work,
the effect of varying stoichiometry of CsPbI<sub>2</sub>Br perovskite
on film quality such as the grain size, presence of impurities and
nature of impurity grains, photoluminescence, morphology, and elemental
distribution are studied. Details on how to vary the stoichiometry
during the dual source thermal evaporation process are reported. It
is found that the air stability of CsPbI<sub>2</sub>Br film correlates
with the CsBr-to-PbI<sub>2</sub> deposition rate ratio, in which the
CsBr-rich CsPbI<sub>2</sub>Br is the most stable upon air exposure,
while the stoichiometrically balanced CsPbI<sub>2</sub>Br perovskite
film gives the best photovoltaic performance. The encapsulated device
maintains 90% of the initial performance after 240 h damp and heat
test at 85 °C and 85% relative humidity
Overcoming the Challenges of Large-Area High-Efficiency Perovskite Solar Cells
For the first time, we report large-area
(16 cm<sup>2</sup>) independently
certified efficient single perovskite solar cells (PSCs) by overcoming
two challenges associated with large-area perovskite solar cells.
The first challenge of realizing a homogeneous and densely packed
perovskite film over a large area is overcome by using an antisolvent
spraying process. The second challenge of removing the series resistance
limitation of transparent conductor is overcome by incorporating a
metal grid designed using a semidistributed diode model. A 16 cm<sup>2</sup> perovskite solar device at the cell level rather than at
the module level is demonstrated using the modified solution process
in conjunction with the use of a metal grid. The cell is independently
certified to be 12.1% efficient. This work paves the way toward highly
efficient and large perovskite cells without single-junction perovskite
solar cells and silicon–perovskite
tandems
Overcoming the Challenges of Large-Area High-Efficiency Perovskite Solar Cells
For the first time, we report large-area
(16 cm<sup>2</sup>) independently
certified efficient single perovskite solar cells (PSCs) by overcoming
two challenges associated with large-area perovskite solar cells.
The first challenge of realizing a homogeneous and densely packed
perovskite film over a large area is overcome by using an antisolvent
spraying process. The second challenge of removing the series resistance
limitation of transparent conductor is overcome by incorporating a
metal grid designed using a semidistributed diode model. A 16 cm<sup>2</sup> perovskite solar device at the cell level rather than at
the module level is demonstrated using the modified solution process
in conjunction with the use of a metal grid. The cell is independently
certified to be 12.1% efficient. This work paves the way toward highly
efficient and large perovskite cells without single-junction perovskite
solar cells and silicon–perovskite
tandems