In
our day-to-day lives, advances in lightweight and flexible photovoltaics
will promote a new generation of soft electronics and machines requiring
high power-per-weight. Ultrathin flexible perovskite solar cells (F-PSCs)
with high power-per-weight have displayed a unique potential for specific
applications where lower weight, higher flexibility, and conformability
are indispensable. This Review highlights the recent progress and
practical applications of ultrathin and lightweight F-PSCs and demonstrates
the routes toward enhanced device efficiency and improved mechanical
and environmental stability concerning the choice of flexible substrates
and the development of high-performance functional layers and flexible
transparent electrodes. The fabrication technologies for mass production
of efficient F-PSCs at large scale are then summarized, including
continuous roll-to-roll methods integrated with low-temperature process.
Furthermore, the practical applications focused on self-powered wearable
electronic devices, solar-powered miniature unmanned aerial vehicles,
and even solar modules operating in near-space are elaborated. Finally,
the current challenging issues and future perspective are discussed,
aiming to promote more extensive applications and commercialization
processes for lightweight F-PSCs.
The
cost-efficient and plentiful Na and K resources motivate the
research on ideal electrodes for sodium-ion batteries (SIBs) and potassium-ion
batteries (PIBs). Here, MoSe2 nanosheets perpendicularly
anchored on reduced graphene oxide (rGO) are studied as an electrode
for SIBs and PIBs. Not only does the graphene network serves as a
nucleation substrate for suppressing the agglomeration of MoSe2 nanosheets to eliminate the electrode fracture but also facilitates
the electrochemical kinetics process and provides a buffer zone to
tolerate the large strain. An expanded interplanar spacing of 7.9
Å is conducive to fast alkaline ion diffusion, and the formed
chemical bondings (C–Mo and C–O–Mo) promote the
structure integrity and the charge transfer kinetics. Consequently,
MoSe2@5%rGO exhibits a reversible specific capacity of
458.3 mAh·g–1 at 100 mA·g–1, great cyclability with a retention of 383.6 mAh·g–1 over 50 cycles, and excellent rate capability (251.3 mAh·g–1 at 5 A·g–1) for SIBs. For
PIBs, a high first specific capacity of 365.5 mAh·g–1 at 100 mA·g–1 with a low capacity fading
of 51.5 mAh·g–1 upon 50 cycles and satisfactory
rate property are acquired for MoSe2@10%rGO composite. Ex situ measurements validate that the discharge products
are Na2Se for SIBs and K5Se3 for
PIBs, and robust chemical bonds boost the structure stability for
Na- and K-ion storage. The full batteries are successfully fabricated
to verify the practical feasibility of MoSe2@5%rGO composite.
Metal halide perovskite‐based solar cells have achieved rapidly increasing efficiencies of up to 23.7%. However, it is still far away from the Shockley–Quiesser limit of 33.16%. Tandem solar cells, consisting of two subcells with complementary absorption, are suggested as an alternative to beat this limit due to the fact that a maximum efficiency of 42% can be reached using two subcells with bandgaps of 1.9 eV/1.0 eV, opening up a great potential to develop perovskite‐based tandem solar cells. In this review, the current status of and recent advances in perovskite‐based tandem solar cells are highlighted, including perovskite–silicon, perovskite–perovskite, and perovskite–copper indium gallium selenide (CIGS) integrations. Different configurations, key issues regarding the photoelectric properties, present efficiency limitations, and material design are discussed. The critical role of perovskite bandgap optimization, interface engineering, and recombination layers are also analyzed to outline the roadmaps for future investigation. The current challenging issues and future perspectives are also provided. It is hoped that the findings will provide new perspectives for perovskite‐based tandem solar cells with an unprecedented performance and the opportunity for commercialization.
Lithium‐sulfur (Li‐S) batteries are considered one of the most competitive candidates for the next generation of energy storage devices due to the high theoretical specific capacity and energy density of the sulfur cathode, the abundant resource reserves, and environmental friendliness. However, the S cathode still faces many challenges, such as large volume expansion, low conductivity, and the “shuttle effect” caused by the dissolution and migration of polysulfides. Studies on the cathode are mainly focused on the construction of novel S‐based composites to alleviate the problems mentioned above via physical protection, chemical integration, and electrocatalysts, including S/C, S/metal compounds, and S/conductive polymers. In this Review, the remaining challenges and possible solutions existing in S cathodes are summarized, and the current research progress on various materials design and electrochemical performances improvement are discussed. The future development trend is also proposed.
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