Perovskite solar cells (PSCs) have gained tremendous research interest recently owing to several advantages, including low material cost, facile solution processability, bandgap tunability, and alluring device efficiency. The organic formamidinium (FA) cation‐based perovskites are mainly considered as one of the potential candidates for charge carrier generation due to their excellent properties, such as bandgap and thermal stability than traditional perovskites. However, the inevitable unfavorable polymorphism (i.e., α to δ) at room temperature still forms the basis for numerous research works to allow the fabrication of a high‐quality absorber and enhances the PSCs performance. The studies to resolve the polymorphism and several contemporary techniques (e.g., passivation strategy) with several recent novel fabrication methods presented in this review form the essence of the improvements in PSCs. The absorber morphology also influences the charge‐transfer behavior and the device's lifetime. Therefore, understanding these properties is essential to improve the absorber quality and avoid many defects. This review focuses on the structure and properties of pure and mixed FA perovskites with various halides, mainly the FA cation's role in the absorber composition. And a comprehensive overview of recent FA cation‐based double, triple, and quadrupole PSCs results with proper scientific explanations to understand the device physics.

A green method for an efficient synthesis of water-soluble carbon nanoparticles (CNPs), graphitic shell encapsulated carbon nanocubes (CNCs), Carbon dots (CDs) using Camphor (Cinnamomum camphora) is demonstrated. Here, we describe a competent molecular fusion and fission route for step-wise synthesis of CDs. Camphor on acidification and carbonization forms CNPs, which on alkaline hydrolysis form CNCs that are encapsulated by thick graphitic layers and on further reduction by sodium borohydride yielded CDs. Though excitation wavelength dependent photoluminescence is observed in all the three carbon nanostructures, CDs possess enhanced photoluminescent properties due to more defective carbonaceous structures. The surface hydroxyl and carboxyl functional groups make them water soluble in nature. They possess excellent photostability, higher quantum yield, increased absorption, decreased cytotoxicity and hence can be utilized as a proficient bio imaging agent.

A multifunctional magneto-plasmonic CoFe₂O₄@Au core-shell nanoparticle was developed by iterative-seeding based method. This nanocargo consists of a cobalt ferrite kernel as a core (Nk) and multiple layers of gold as a functionalizable active stratum, (named as Nk@A after fifth iteration). Nk@A helps in augmenting the physiological stability and enhancing surface plasmon resonance (SPR) property. The targeted delivery of Doxorubicin using Nk@A as a nanopayload is demonstrated in this report. The drug release profile followed first order rate kinetics optimally at pH 5.4, which is considered as an endosomal pH of cells. The cellular MR imaging showed that Nk@A is an efficient T₂ contrast agent for both L6 (r₂-118.08 mM⁻¹s⁻¹) and Hep2 (r₂-217.24 mM⁻¹s⁻¹) cells. Microwave based magnetic hyperthermia studies exhibited an augmentation in the temperature due to the transformation of radiation energy into heat at 2.45 GHz. There was an enhancement in cancer cell cytotoxicity when hyperthermia combined with chemotherapy. Hence, this single nanoplatform can deliver 3-pronged theranostic applications viz., targeted drug-delivery, T₂ MR imaging and hyperthermia.

Facile synthesis of superparamagnetic, highly crystalline, manganese ferrite nanocubes (MnNCs) is reported. X-ray diffraction depicts single-phase face-centred cubic spinel and the electron microscopy represents the nearly monodispersed cube-like nanostructure with the size ranging from 18 to 20 nm. Vibrating sample magnetometer shows magnetization field-dependent curves at 300 K exhibiting the superparamagnetic behaviour of NCs with negligible remanence. Furthermore, the biocompatibility of NCs was proved by MTT assay. These unique characteristics make this NCs as a contrast agent ideally suited for T₂-weighted MR imaging. This novel method of synthesizing NCs proves to be very attractive for various biomedical applications because of their outstanding stability and biocompatibility.