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.