Surface Modulation via Conjugated Bithiophene Ammonium Salt for Efficient Inverted Perovskite Solar Cells.

The metal halide perovskite absorbers are prone to surface defects, which severely limit the power conversion efficiencies (PCEs) and the operational stability of the perovskite solar cells (PSCs). Herein, trace amounts of bithiophene propylammonium iodide (bi-TPAI) are applied to modulate the surface properties of the gas-quenched perovskite. It is found that the bi-TPAI surface treatment has negligible impact on the perovskite morphology, but it can induce a defect passivation effect and facilitate the charge carrier extraction, contributing to the gain in the open-circuit voltage (Voc) and fill factor. As a result, the PCE of the gas-quenched sputtered NiOx-based inverted PSCs is enhanced from the initial 20.0% to 22.0%. Most importantly, the bi-TPAI treatment can largely alleviate or even eliminate the burn-in process during the maximum power point tracking measurement, improving the operational stability of the devices.

Stabilization of FAPbI3 with Multifunctional Alkali-Functionalized Polymer.

The defects located at the interfaces and grain boundaries (GBs) of perovskite films are detrimental to the photovoltaic performance and stability of perovskite solar cells. Manipulating the perovskite crystallization process and tailoring the interfaces with molecular passivators are the main effective strategies to mitigate performance loss and instability. Herein, a new strategy is reported to manipulate the crystallization process of FAPbI3 -rich perovskite by incorporating a small amount of alkali-functionalized polymers into the antisolvent solution. The synergic effects of the alkali cations and poly(acrylic acid) anion effectively passivate the defects on the surface and GBs of perovskite films. As a result, the rubidium (Rb)-functionalized poly(acrylic acid) significantly improves the power conversion efficiency of FAPbI3 perovskite solar cells to approaching 25% and reduces the risk of lead ion (Pb2+ ) leakage continuously via the strong interaction between CO bonds and Pb2+ . In addition, the unencapsulated device shows enhanced operational stability, retaining 80% of its initial efficiency after 500 h operation at maximum power point under one-sun illumination.

A universal co-solvent dilution strategy enables facile and cost-effective fabrication of perovskite photovoltaics.

Cost management and toxic waste generation are two key issues that must be addressed before the commercialization of perovskite optoelectronic devices. We report a groundbreaking strategy for eco-friendly and cost-effective fabrication of highly efficient perovskite solar cells. This strategy involves the usage of a high volatility co-solvent, which dilutes perovskite precursors to a lower concentration (<0.5 M) while retaining similar film quality and device performance as a high concentration (>1.4 M) solution. More than 70% of toxic waste and material cost can be reduced. Mechanistic insights reveal ultra-rapid evaporation of the co-solvent together with beneficial alteration of the precursor colloidal chemistry upon dilution with co-solvent, which in-situ studies and theoretical simulations confirm. The co-solvent tuned precursor colloidal properties also contribute to the enhancement of the stability of precursor solution, which extends its processing window thus minimizing the waste. This strategy is universally successful across different perovskite compositions, and scales from small devices to large-scale modules using industrial spin-coating, potentially easing the lab-to-fab translation of perovskite technologies.

Molecular-Level Insight into Correlation between Surface Defects and Stability of Methylammonium Lead Halide Perovskite Under Controlled Humidity.

Perovskite-based photovoltaics (PVs) have garnered tremendous interest, enabling power conversion efficiencies exceeding 25%. Although much of this success is credited to the exploration of new compositions, defects passivation and process optimization, environmental stability remains an important bottleneck to be solved. The underlying mechanisms of thermal and humidity-induced degradation are still far from a clear understanding, which poses a severe limitation to overcome the stability issues. Herein, in situ X-ray diffraction (XRD), in operando liquid-cell transmission electron microscopy (TEM) and ex situ solid-state (ss)NMR spectroscopy are combined with time-resolved spectroscopies to reveal new insights about the degradation mechanisms of methylammonium lead halide (MAPbI3 ) under 85% relative humidity (RH) at different length scales. Liquid-cell TEM enables the live visualizations from meso-to-nanoscale transformation between the perovskite particles and water molecules, which are corroborated by the changes in local structures at sub-nanometer distances by ssNMR and longer range by XRD. This work clarifies the role of surface defects and the significance of their passivation to prevent hydration and decomposition reactions.

Nanoscale interfacial engineering enables highly stable and efficient perovskite photovoltaics.

We present a facile molecular-level interface engineering strategy to augment the long-term operational and thermal stability of perovskite solar cells (PSCs) by tailoring the interface between the perovskite and hole transporting layer (HTL) with a multifunctional ligand 2,5-thiophenedicarboxylic acid. The solar cells exhibited high operational stability (maximum powering point tracking at one sun illumination) with a stabilized T S80 (the time over which the device efficiency reduces to 80% after initial burn-in) of ≈5950 h at 40 °C and a stabilized power conversion efficiency (PCE) over 23%. The origin of high device stability and performance is correlated to the nano/sub-nanoscale molecular level interactions between ligand and perovskite layer, which is further corroborated by comprehensive multiscale characterization. These results provide insights into the modulation of the grain boundaries, local density of states, surface bandgap, and interfacial recombination. Chemical analysis of aged devices showed that molecular passivation suppresses interfacial ion diffusion and inhibits the photoinduced I2 release that irreversibly degrades the perovskite. The interfacial engineering strategies enabled by multifunctional ligands can expedite the path towards stable PSCs.

Combined Precursor Engineering and Grain Anchoring Leading to MA-Free, Phase-Pure, and Stable α-Formamidinium Lead Iodide Perovskites for Efficient Solar Cells.

α-Formamidinium lead iodide (α-FAPbI3 ) is one of the most promising candidate materials for high-efficiency and thermally stable perovskite solar cells (PSCs) owing to its outstanding optoelectrical properties and high thermal stability. However, achieving a stable form of α-FAPbI3 where both the composition and the phase are pure is very challenging. Herein, we report on a combined strategy of precursor engineering and grain anchoring to successfully prepare methylammonium (MA)-free and phase-pure stable α-FAPbI3 films. The incorporation of volatile FA-based additives in the precursor solutions completely suppresses the formation of non-perovskite δ-FAPbI3 during film crystallization. Grains of the desired α-phase are anchored together and stabilized when 4-tert-butylbenzylammonium iodide is permeated into the α-FAPbI3 film interior via grain boundaries. This cooperative scheme leads to a significantly increased efficiency close to 21 % for FAPbI3 perovskite solar cells. Moreover, the stabilized PSCs exhibit improved thermal stability and maintained ≈90 % of their initial efficiency after storage at 50 °C for over 1600 hours.

Multimodal host-guest complexation for efficient and stable perovskite photovoltaics.

Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host-guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs+ ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host-guest complex. The resulting solar cells show power conversion efficiencies exceeding 24% and enhanced operational stability, maintaining over 95% of their performance without encapsulation for 500 h under continuous operation. Moreover, the host contributes to binding lead ions, reducing their environmental impact. This supramolecular strategy illustrates the broad implications of host-guest chemistry in photovoltaics.

Crown Ether Modulation Enables over 23% Efficient Formamidinium-Based Perovskite Solar Cells.

The use of molecular modulators to reduce the defect density at the surface and grain boundaries of perovskite materials has been demonstrated to be an effective approach to enhance the photovoltaic performance and device stability of perovskite solar cells. Herein, we employ crown ethers to modulate perovskite films, affording passivation of undercoordinated surface defects. This interaction has been elucidated by solid-state nuclear magnetic resonance and density functional theory calculations. The crown ether hosts induce the formation of host-guest complexes on the surface of the perovskite films, which reduces the concentration of surface electronic defects and suppresses nonradiative recombination by 40%, while minimizing moisture permeation. As a result, we achieved substantially improved photovoltaic performance with power conversion efficiencies exceeding 23%, accompanied by enhanced stability under ambient and operational conditions. This work opens a new avenue to improve the performance and stability of perovskite-based optoelectronic devices through supramolecular chemistry.

Compositional and Interface Engineering of Organic-Inorganic Lead Halide Perovskite Solar Cells.

Power conversion efficiency (PCE) of the perovskite solar cells (PSCs) has remarkably been increased from 3.1% to 25.2%. The fast expansion of the PSCs has been along with the development of compositional and interface engineering, which has been playing a critical role. For the PSCs with record high-efficiency and stability, the perovskite absorber layer has been changed from the initial MAPbI3- to FAPbI3-based compositions. Owing to the enormous engineering works, perovskite absorber layers with monolithic grains could be achieved, in which the interior defects are negligible compared with the surface defects. Therefore, interface engineering, which can passivate the surface defects and/or isolate the perovskite from the environmental moistures, has been playing a more and more important role to further boost the PCE and stability of the PSCs. Herein, a compact review study of the compositional and interface engineering is presented and promising strategies and directions of the PSCs are discussed.

Facile Synthesis of a Furan-Arylamine Hole-Transporting Material for High-Efficiency, Mesoscopic Perovskite Solar Cells.

A novel hole-transporting molecule (F101) based on a furan core has been synthesized by means of a short, high-yielding route. When used as the hole-transporting material (HTM) in mesoporous methylammonium lead halide perovskite solar cells (PSCs) it produced better device performance than the current state-of-the-art HTM 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). The F101-HTM-based device exhibited both slightly higher Jsc (19.63 vs. 18.41 mA cm(-2) ) and Voc (1.1 vs. 1.05 V) resulting in a marginally higher power conversion efficiency (PCE) (13.1 vs. 13 %). The steady-state and time-resolved photoluminescence show that F101 has significant charge extraction ability. The simple molecular structure, short synthesis route with high yield and better performance in devices makes F101 an excellent candidate for replacing the expensive spiro-OMeTAD as HTM in PSCs.

Interfacial Charge Transfer Anisotropy in Polycrystalline Lead Iodide Perovskite Films.

Solar cells based on organic-inorganic lead iodide perovskite (CH3NH3PbI3) exhibit remarkably high power conversion efficiency (PCE). One of the key issues in solution-processed films is that often the polycrystalline domain orientation is not well-defined, which makes it difficult to predict energy alignment and charge transfer efficiency. Here we combine ab initio calculations and photoelectron spectroscopy to unravel the electronic structure and charge redistribution at the interface between different surfaces of CH3NH3PbI3 and typical organic hole acceptor Spiro-OMeTAD and electron acceptor PCBM. We find that both hole and electron interfacial transfer depend strongly on the CH3NH3PbI3 surface orientation: while the (001) and (110) surfaces tend to favor hole injection to Spiro-OMeTAD, the (100) surface facilitates electron transfer to PCBM due to surface delocalized charges and hole/electron accumulation at the CH3NH3PbI3/organic interfaces. Molecular dynamic simulations indicate that this is due to strong orbital interactions under thermal fluctuations at room temperature, suggesting the possibility to further improve charge separation and extraction in perovskite-based solar cells by controlling perovskite film crystallization and surface orientation.

Revised guidelines on management of antenatal hydronephrosis.

Widespread antenatal screening has resulted in increased detection of anomalies of the kidneys and urinary tract. The present guidelines update the recommendations published in 2000. Antenatal hydronephrosis (ANH) is transient and resolves by the third trimester in almost one-half cases. The presence of oligohydramnios and additional renal or extrarenal anomalies suggests significant pathology. All patients with ANH should undergo postnatal ultrasonography; the intensity of subsequent evaluation depends on anteroposterior diameter (APD) of the renal pelvis and/or Society for Fetal Urology (SFU) grading. Patients with postnatal APD exceeding 10 mm and/or SFU grade 3-4 should be screened for upper or lower urinary tract obstruction and vesicoureteric reflux. Infants with vesicoureteric reflux should receive antibiotic prophylaxis through the first year of life, and their parents counseled regarding the risk of urinary tract infections. The management of patients with pelviureteric junction or vesicoureteric junction obstruction depends on clinical features and results of sequential ultrasonography and radionuclide renography. Surgery is considered in patients with increasing renal pelvic APD and/or an obstructed renogram with differential renal function <35-40% or its subsequent decline. Further studies are necessary to clarify the role of prenatal intervention, frequency of follow up investigations and indications for surgery in these patients.

Doctors and Padma awards.

UNLABELLED: BACKGROUND; The announcement of the annual Padma awards in January always generates a great deal of interest as well as controversy and, some believe that many good candidates are excluded and many less deserving ones included. We analysed the recipients in the field of medicine to determine whether or not a pattern emerged regarding who were bestowed these honours. We were not able to objectively evaluate whether or not the honours were 'deserved'. METHODS: We obtained and then analysed the list of awardees from newspapers and the official website of the Ministry of Home Affairs. Between 2000 and 2010, a total of 1166 awards were announced, of which 157 (13.4%) were in the field of medicine. We excluded foreigners and those from 'alternative' fields (20), and evaluated the remaining 137 in detail. RESULTS: Sixty-two (45.3%) recipients were from Delhi, 18 (13.1%) from Maharashtra and 17 (12.4%) from Tamil Nadu. Of the 137 awardees, 31 (22.6%) were cardiologists or cardiac surgeons. Many large states of the country, such as West Bengal, Gujarat, Rajasthan, Madhya Pradesh, Punjab and Haryana, did not have a single awardee. CONCLUSION: The over-representation of Delhi and cardiology in the Padma awards for medicine suggests that their distribution is not entirely fair.

Laparoscopic repair of paraesophageal hiatus hernia in infancy.

Paraesophageal hiatus hernia (PEHH) is an uncommon type of diaphragmatic hernia in the pediatric age group. Two patients aged 5-months and 8-months presented with respiratory symptoms and underwent a laparoscopic repair. Preoperative assessment included chest x-ray and CT scan. We suggest that laparoscopic repair of PEHH in infants is safe and preferred mode of the treatment.

Scapular bronchogenic cyst.

We report a rare case of a 3-year-old male child with scapular bronchogenic cyst. The cyst was excised because of associated pain and discharge from the swelling. Till date, 64 cases of cutaneous bronchogenic cyst have been reported in the literature. Only 12 of these patients had lesion located in periscapular area. The treatment is surgical as it can undergo malignant transformation.