Perovskite Solar Fibers:Current Status,Issues and Challenges

Perovskite-based solar cells with high power conversion efficiencies(PCEs)are currently being demonstrated in solid-state device designs.Their elevated performances can possibly be attained with different non-standard geometries,for example,the fiber-shaped perovskite solar cells,in the light of careful design and engineering.Fiber-shaped solar cells are promising in smart textiles energy harvesting towards next-generation electronic applications and devices.They can be made with facile process and at low cost.Recently,fiber-shaped perovskite solar devices have been reported,particularly with the focus on the proof-of-concept in such non-traditional architectures.In this line,there are so many technical aspects which need to be addressed,if these photovoltaic(PV)cells are to be industrialized and produced massively.Herein,a well-organized and comprehensive discussion about the reported devices in this arena is presented.The challenges that need to be addressed,the possible solutions and the probable applications of these PV cells are also discussed.More still,the perovskite fiber-shaped PV cells with other fiber PV devices reported in literature in terms of their scope,characteristic designs,performances,and other technical considerations have been summarised.

Chlorine‑Rich Substitution Enabled 2D3D Hybrid Perovskites for High Efficiency and Stability in Sn‑Based Fiber‑Shaped Perovskite Solar Cells

Despite the impressive power conversion efficiency(PCE)beyond 25.5%,perovskite solar cells,especially the Sn-based variants,are poorly stable under normal operating conditions compared with the market-dominant silicon solar cells that can last for over 25 years.2D3D hybrid perovskite materials are one of the best options to overcome the instability chal-lenge without compromising efficiency.Indeed,a record performance of 1 year was reported in Pb-based 2D3D planar per-ovskite devices.However,the reaction between 2 and 3D perovskite molecules requires high temperatures(-300°C)and increased reaction time(-24 h)to achieve high-quality 2D3D hybrid perovskites.Herein,we base on the ability of chlorine to displace iodine from its ionic compounds in solutions to utilize chloride ions as catalysts for speeding up the reaction between iodine-based 2D and 3D perovskite molecules.The approach reduces the reaction time to-20 min and the reaction temperature to-100°C with the formation of high-quality 2D3D hybrid perovskites,free from pure 2D traces.Integrating the synthesized 2D3D hybrid perovskite material with 50%chlorine doping in a fiber-shaped solar cell architecture yielded the highest reported PCE of 11.96%in Sn-based fiber-shaped perovskite solar cells.The unencapsulated and encapsulated fiber-shaped solar cells could maintain 75%and 95.5%of their original PCE,respectively,after 3 months under room light and relative humidity of 35–40%,revealing the champion stability in Sn-based perovskite solar devices.The solar yarn also demonstrated constant energy output under changing light incident angles(0–180°).

Scalable van der Waals graphene films for electro-optical regulation and thermal camouflage

Graphene exhibits enormous advantages in mid-infrared(MIR)regulation because of the active control,precise regulation,and large modulation depth.Such graphene films are prepared via chemical vapor deposition(CVD)or reduction,which cannot realize large-scale production and limit the applications.Graphene films with van der Waals(vdW)structure enable excellent mechanical and electrical performance for flexible electrodes and electronics and might be a candidate for MIR regulation.However,current techniques for preparing vdW graphene films require binder or solution assistance,resulting in chemical residues and performance degradation.Here,a new strategy for preparing large-area vdW graphene films by simple mechanical adhesion without any additives was proposed.By selecting the carriers and substrates with proper fracture energies,graphene nanosheets can be transferred from one polymer to another with a layer-by-layer structure.The obtained graphene films possess desired thickness and comparable electrical conductivity(92.8±4.6 ohm sq–1)with those by chemical vapor deposition.They are of high compactness even for ions to intercalate reversibly,which exhibit excellent electrochemical activity and electro-optical regulation capability,effectively suppressing 90%thermal radiation.This strategy can be extended to prepare high-performance vdW graphene films on various polymer substrates and used for sustainable and smart electro-optical applications.