a b s t r a c tThe structure and dynamics of negatively charged nucleic acids strongly correlate with the concentration and charge of the oppositely charged counterions. It is well known that the structural collapse of DNA is favoured in the presence of additional salt, a source of excess oppositely charged ions. Under such conditions single stranded DNA adopts a collapsed coil like conformation, typically characterized by stacking base pairs. Using atomistic molecular dynamics simulation, we demonstrate that in the presence of additional divalent salt (MgCl 2 ) single stranded DNA with base sequence 5 0 -CGCGAATTCGCG-3 0 (Dickerson Drew dodecamer) initially collapses and then expands with increasing salt concentration. This is due to the overcharging induced DNA chain swelling, a dominant factor at a higher divalent salt concentration. In a nutshell, our simulations show how in the presence of divalent salt, non-sequential base stacking and overcharging competes and affect single stranded DNA dynamics unlike a monovalent salt.

Effective conversion of solar photons into electrical power through the development of smart and eco‐friendly materials is one of the most extensively researched methods for generating renewable energy. In this work, an inorganic lead‐free double perovskite Cs2SnI6 material is employed as an active layer for solar cell applications, together with GO (graphene oxide) as electron transport layer (ETL) and Cu2O as hole transport layer (HTL). In order to find the most efficient photovoltaic device, a detailed theoretical study using the SCAPS‐1D simulation program is conducted. The device performance is monitored and analyzed by considering various HTLs, doping density in active layer, light intensity, ETL thickness, operating temperature, parasitic resistances, and the role of defects on device performance. The optimized device displays a power conversion efficiency of 23.64% with excellent photovoltaic characteristics. This theoretical study reveals that Cs2SnI6 can be a promising choice for solar cell applications as a lead‐free double perovskite material.

Perovskite solar cells (PSCs) are considered as one of the most promising alternatives for existing solar cells due to its excellent optoelectronic properties and high efficiency. However, lead has posed a serious issue due to its toxicity which may hinder the commercial use of lead‐based perovskite solar panels/arrays. There has been substantial work progress to find an environment‐friendly alternative metal ion to replace lead. Tin (Sn)‐based PSCs have been successfully synthesized and optimized with high efficiency, making it the most promising active material for lead‐free PSCs. In this review, the role of J–V hysteresis in tin halide PSCs is discussed from the perspective of system structure, working concepts, and interfacial carrier dynamics in detail. The problem of hysteresis in PSCs is closely linked to ion migration, ferroelectric effects, capacitive effects, and trap‐assisted recombination processes, which are highlighted in this review. Further, remediation to reduce the hysteresis by various strategies is explained for tin‐based perovskites. The core focus of this review is to analyze the deterioration of device performance and stability caused due to the generation of defects in the perovskite films, leading to a time‐dependent hysteresis of the current–voltage curves.

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