Halide perovskites are a compelling candidate for the next generation of clean energy harvesting technologies thanks to their low cost, facile fabrication and outstanding semiconductor properties. However, photovoltaic device efficiencies are still below practical limits and long-term stability challenges hinder their practical application. Current evidence suggests that strain in halide perovskites is a key factor in dictating device efficiency and stability. Here, we outline the fundamentals of strain within halide perovskites relevant to photovoltaic applications and rationalize approaches to characterize the phenomenon. We examine recent breakthroughs in eliminating the adverse impacts of strain, enhancing both device efficiencies and operational stabilities. Finally, we discuss further challenges and outline future research directions for placing stress and strain studies at the forefront of halide perovskite research. An extensive understanding of strain in halide perovskite is needed, which would allow effective strain management and drive further enhancements in efficiencies and stabilities of perovskite photovoltaics.

Stable but not quite cubic The black, photoactive phase of formamidinium (FA) perovskites, which is usually stabilized by cation alloying to avoid the formation of inactive hexagonal phases, is assumed to be cubic. High-resolution microscopy studies by Doherty et al . using nanoscale probes revealed that these FA-rich phases are not cubic but rather undergo slight tilting (by two degrees) of the octahedra. Black phases can have localized regions of hexagonal phases that nucleate degradation. Surface-bound ethylenediaminetetraacetic acid stabilized the tilted phase of pure FA lead triiodide against environmental degradation. —PDS

Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7% in single junction and 29.8% in tandem perovskite/silicon cells 1,2 , yet retaining such performance under continuous operation has remained elusive 3 . Here, we develop a multimodal microscopy toolkit to reveal that in leading formamidinium-rich perovskite absorbers, nanoscale phase impurities including hexagonal polytype and lead iodide inclusions are not only traps for photo-excited carriers which themselves reduce performance 4,5 , but via the same trapping process are sites at which photochemical

It has been recently shown that the strain gradient is able to separate the light-excited electron-hole pairs in semiconductors, but how it affects the photoelectric properties of the photo-active materials remains an open question. Here, we demonstrate the critical role of the strain gradient in mediating local photoelectric properties in the strained BiFeO 3 thin films by systematically characterizing the local conduction with nanometre lateral resolution in both dark and illuminated conditions. Due to the giant strain gradient manifested at the morphotropic phase boundaries, the associated flexo-photovoltaic effect induces on one side an enhanced photoconduction in the R -phase, and on the other side a negative photoconductivity in the morphotropic -phase. This work offers insight and implication of the strain gradient on the electronic properties in both optoelectronic and photovoltaic devices.

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Breast cancer is ranked the top in types of cancer that affects internationally. It affects up to 1 in 13 women during their lifetime. Physiotherapy is one of the major sources of recovery in patients of Mastectomy in terms of pain, ranges, and function. OBJECTIVE: To compare the effects of pre-operative shoulder rehabilitation program versus post-operative mastectomy patients. METHODS: This was a randomized clinical trial. The study setting was Oncology Department, Mayo Hospital Lahore, Shokat Khanum and Gulab Devi Hospital Lahore. The study was completed in 6 months. Total 50 subjects were allocated in two groups using lottery method of randomization. Patient with age less than 40 years, diagnosed with breast cancer were included, while those with associated signs of musculoskeletal problems, autoimmune systemic disease and advanced medical problem was excluded. Group A received set of exercises comprised of range of motion exercises and lymph edema education pre and post operatively. Group B received post rehabilitation exercises only. Data was analyzed by SPSS 16.0. Independent t test was applied to analyze between group differences and paired sample t test to see within group improvement. Descriptive statistics was in form of mean, variance and appropriate graphs. RESULTS: Independent sample test results regarding post interventional disability of arm, shoulder, and hand (DASH) score showed significant p value 0.000 with a mean difference of 23.28000 while assuming equal variances. The mean and standard deviation of pain score was 3.76 (SD+0.778) pre/post combination group and post-operative rehabilitation program alone 4.1200 (SD+0.78102) with a statistically equal improvement in both groups (0.109). CONCLUSION: The study concluded that there was significant difference with better outcomes in terms of improvement in function, pain and range in patients having combination protocol i.e. pre-operative and post-operative rehab protocol in patient of mastectomy as compared to post-operative rehabilitation protocol alone.