Highest reported efficiency cesium lead halide perovskite solar cells are realized by tuning the bandgap and stabilizing the black perovskite phase at lower temperatures. CsPbI2Br is employed in a planar architecture device resulting in 9.8% power conversion efficiency and over 5% stabilized power output. Offering substantially enhanced thermal stability over their organic based counterparts, these results show that all‐inorganic perovskites can represent a promising next step for photovoltaic materials.
Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. State-of-the-art monolithic two-terminal perovskite/silicon tandem devices have so far featured silicon bottom cells that are polished on their front side to be compatible with the perovskite fabrication process. This concession leads to higher potential production costs, higher reflection losses and non-ideal light trapping. To tackle this issue, we developed a top cell deposition process that achieves the conformal growth of multiple compounds with controlled optoelectronic properties directly on the micrometre-sized pyramids of textured monocrystalline silicon. Tandem devices featuring a silicon heterojunction cell and a nanocrystalline silicon recombination junction demonstrate a certified steady-state efficiency of 25.2%. Our optical design yields a current density of 19.5 mA cm thanks to the silicon pyramidal texture and suggests a path for the realization of 30% monolithic perovskite/silicon tandem devices.
We
report a colloidal synthesis approach to CsPbBr3 nanoplatelets
(NPLs). The nucleation and growth of the platelets, which takes place
at room temperature, is triggered by the injection of acetone in a
mixture of precursors that would remain unreactive otherwise. The
low growth temperature enables the control of the plate thickness,
which can be precisely tuned from 3 to 5 monolayers. The strong two-dimensional
confinement of the carriers at such small vertical sizes is responsible
for a narrow PL, strong excitonic absorption, and a blue shift of
the optical band gap by more than 0.47 eV compared to that of bulk
CsPbBr3. We also show that the composition of the NPLs
can be varied all the way to CsPbBr3 or CsPbI3 by anion exchange, with preservation of the size and shape of the
starting particles. The blue fluorescent CsPbCl3 NPLs represent
a new member of the scarcely populated group of blue-emitting colloidal
nanocrystals. The exciton dynamics were found to be independent of
the extent of 2D confinement in these platelets, and this was supported
by band structure calculations.
Perovskite/silicon tandem solar cells are increasingly recognized as promising candidates for next‐generation photovoltaics with performance beyond the single‐junction limit at potentially low production costs. Current designs for monolithic tandems rely on transparent conductive oxides as an intermediate recombination layer, which lead to optical losses and reduced shunt resistance. An improved recombination junction based on nanocrystalline silicon layers to mitigate these losses is demonstrated. When employed in monolithic perovskite/silicon heterojunction tandem cells with a planar front side, this junction is found to increase the bottom cell photocurrent by more than 1 mA cm−2. In combination with a cesium‐based perovskite top cell, this leads to tandem cell power‐conversion efficiencies of up to 22.7% obtained from J–V measurements and steady‐state efficiencies of up to 22.0% during maximum power point tracking. Thanks to its low lateral conductivity, the nanocrystalline silicon recombination junction enables upscaling of monolithic perovskite/silicon heterojunction tandem cells, resulting in a 12.96 cm2 monolithic tandem cell with a steady‐state efficiency of 18%.
Solar cells based on organic-inorganic perovskite semiconductor materials have recently made rapid improvements in performance, with the best cells performing at over 20% efficiency. With such rapid progress, questions such as cost and solar cell stability are becoming increasingly important to address if this new technology is to reach commercial deployment. The moisture sensitivity of commonly used organic-inorganic metal halide perovskites has especially raised concerns. Here, we demonstrate that the hygroscopic lithium salt commonly used as a dopant for the hole transport material in perovskite solar cells makes the top layer of the devices hydrophilic and causes the solar cells to rapidly degrade in the presence of moisture. By using novel, low cost, and hydrophobic hole transporters in conjunction with a doping method incorporating a preoxidized salt of the respective hole transporters, we are able to prepare efficient perovskite solar cells with greatly enhanced water resistance.
High efficiency triple-junction solar
cells are currently made
of III–V semiconductors using expensive deposition methods.
Perovskite/perovskite/silicon monolithic triple-junction solar cells
could be a lower-cost alternative as no epitaxial growth is required.
We demonstrate here that such devices can be realized using textured
crystalline silicon bottom cells for optimal light management. By
changing the perovskite absorbers composition and recombination junctions
to make them compatible with the subsequent fabrication steps, triple-junction
devices with open-circuit voltage up to 2.69 V are realized. To illustrate
the applicability of the technology, we show how the band gaps and
thicknesses of the top and middle cells can be modified to approach
current-matching conditions. The limitations of these devices are
discussed, as well as strategies to make them competitive with III–V
triple-junction cells. The concepts presented here are a first step
toward high-efficiency, high-voltage, and low-cost triple-junction
photovoltaics.
Tandem
photovoltaic devices based on perovskite and crystalline
silicon (PK/c-Si) absorbers have the potential to push commercial
silicon single junction devices beyond their current efficiency limit.
However, their scale-up to industrially relevant sizes is largely
limited by current fabrication methods which rely on evaporated metallization
of the front contact instead of industry standard screen-printed silver
grids. To tackle this challenge, we demonstrate how a low-temperature
silver paste applied by a screen-printing process can be used for
the front metal grid of two-terminal perovskite–silicon tandem
structures. Small-area tandem devices with such printed front metallization
show minimal thermal degradation when annealed up to 140 °C in
air, resulting in silver bulk resistivity of <1 × 10–5 Ω·cm. This printed metallization is then exploited in
the fabrication of large area PK/c-Si tandems to achieve a steady-state
efficiency of 22.6% over an aperture area of 57.4 cm2 with
a two-bus bar metallization pattern. This result demonstrates the
potential of screen-printing metal contacts to enable the realization
of large area PK/c-Si tandem devices.
Optimization of the physical and electronic properties of organic semiconductors is a key step in improving the performance of organic light emitting diodes, organic photovoltaics, organic field effect transistors, and other electronic devices. Separate tuning of the physical and electronic properties of these organic semiconductors can be achieved by the hybridization of organo-silicon structures (silicones, siloxanes, silsesquioxanes) with organic semiconductors. Common chemical means to achieve this hybridization are summarized while a large range of literature examples are covered to demonstrate the range and flexibility of this synthetic strategy.
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