Coherent growth of high-Miller-index facets enhances perovskite solar cells.

Obtaining micron-thick perovskite films of high quality is key to realizing efficient and stable positive (p)-intrinsic (i)-negative (n) perovskite solar cells1,2, but it remains a critical challenge. Here, we report an effective method for producing high-quality, micron-thick formamidinium-based perovskite films by forming coherent grain boundaries, where high-Miller-index-oriented grains grow on the low-Miller-index-oriented grains in a stabilized atmosphere. The resulting micron-thick perovskite films, with enhanced grain boundaries and grains, showed stable material properties and outstanding optoelectronic performances. The small-area solar cells achieved efficiencies of 26.1%. The 1-square-centimeter devices and 5 cm × 5 cm minimodules delivered efficiencies of 24.3% and 21.4%, respectively. The devices processed in a stabilized atmosphere presented a high reproducibility across all four seasons. The encapsulated devices exhibited superior long-term stability under both light and thermal stressors in ambient air.

Reactive Passivation of Wide-Bandgap Organic-Inorganic Perovskites with Benzylamine.

While amines are widely used as additives in metal-halide perovskites, our understanding of the way amines in perovskite precursor solutions impact the resultant perovskite film is still limited. In this paper, we explore the multiple effects of benzylamine (BnAm), also referred to as phenylmethylamine, used to passivate both FA0.75Cs0.25Pb(I0.8Br0.2)3 and FA0.8Cs0.2PbI3 perovskite compositions. We show that, unlike benzylammonium (BnA+) halide salts, BnAm reacts rapidly with the formamidinium (FA+) cation, forming new chemical products in solution and these products passivate the perovskite crystal domains when processed into a thin film. In addition, when BnAm is used as a bulk additive, the average perovskite solar cell maximum power point tracked efficiency (for 30 s) increased to 19.3% compared to the control devices 16.8% for a 1.68 eV perovskite. Under combined full spectrum simulated sunlight and 65 °C temperature, the devices maintained a better T80 stability of close to 2500 h while the control devices have T80 stabilities of <100 h. We obtained similar results when presynthesizing the product BnFAI and adding it directly into the perovskite precursor solution. These findings highlight the mechanistic differences between amine and ammonium salt passivation, enabling the rational design of molecular strategies to improve the material quality and device performance of metal-halide perovskites.

A mixed-methods study on risk perception and safety practices among unorganized construction workers in a municipal area of West Bengal.

BACKGROUND: The construction industry in India heavily relies on unorganized workers, who often lack adequate access to safety measures, placing them at significant risk of accidents and injuries. The objective was to determine risk perceptions of construction workers, and explore their safety practices, facilitators, and barriers. METHODS: A mixed-methods approach with a convergent parallel design (QUAN + qual) was undertaken. Quantitative strand included face-to-face interviews with 203 randomly selected building construction workers from 10 construction sites in five selected municipal wards in Kolkata. Questions pertained to socio-demographics, occupational characteristics, risk perception, and safety practices. The qualitative arm involved key informant interviews to unravel the facilitators and barriers affecting safety practices and nonparticipant observation. RESULTS: The perceived risk for respiratory problems due to dust, pain from carrying loads, slips, trips or falls, and heat-related illnesses was in the medium- to high category for 64.0%, 58.6%, 39.9%, and 36.5% of the study participants, respectively. However, the safety practices for these respective domains were in the good practice category for 6.9%, 4.9%, 54.2%, and 34.5% of the workers. From the qualitative arm, it was evident that availability of PPE, a conducive environment, and availability of worker-friendly technology could be important predictors of safety practices. Barriers such as time constraints and feasibility due to discomfort and expenditure were also identified. CONCLUSION: Despite high-risk perception, safety practices were not consistently good among construction workers. Further research is crucial to enhance the health and safety of unorganized workers in India.

Respiratory Morbidity Among Seed-Processing Industry Workers: A Cross-Sectional Study in Rural West Bengal, 2022-2023.

Background: Seed processing workers are exposed to dust particles generated during the processing of seeds, which can have adverse effects on their respiratory health. Aim: to estimate the prevalence and patterns of respiratory morbidity among seed processing workers in Hooghly district, West Bengal, India, and to explore their use of respiratory personal protective equipment (PPE). Methods: A cross sectional observational study was conducted in 5 seed processing plants from December 2022 to February 2023. A sample size of 129 workers was selected using probability proportionate to population size to select seed processing plants and simple random sampling to select workers at selected plants. Data on sociodemographic characteristics, occupational profile, substance use patterns, respiratory PPE use, and respiratory symptoms were collected through structured interviews. Spirometry was performed with a hand held tabletop spirometer (RMS Helios 401) to assess respiratory function. Results: 52.7% of participants reported at least one chronic respiratory symptom, while 17.1% had evident respiratory morbidity based on spirometry results, with most having restrictive patterns (10.1%). Multivariable regression analysis revealed that factors associated with respiratory morbidity included increasing work years of exposure [1.10 (1.02 1.18)], irregular use of respiratory PPE [4.36 (1.22 15.57)], and primary or below education level [6.09 (1.38 26.98)]. Conclusion: The study highlights the high prevalence of respiratory symptoms and morbidity among seed processing workers. It emphasizes the importance of implementing effective respiratory protection measures and raising awareness about occupational lung diseases in this industry. Further research and interventions are needed to improve the respiratory health and well being of seed processing workers.

Bandgap-universal passivation enables stable perovskite solar cells with low photovoltage loss.

The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (>90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino-silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane-treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.

Open-circuit and short-circuit loss management in wide-gap perovskite p-i-n solar cells.

In this work, we couple theoretical and experimental approaches to understand and reduce the losses of wide bandgap Br-rich perovskite pin devices at open-circuit voltage (VOC) and short-circuit current (JSC) conditions. A mismatch between the internal quasi-Fermi level splitting (QFLS) and the external VOC is detrimental for these devices. We demonstrate that modifying the perovskite top-surface with guanidinium-Br and imidazolium-Br forms a low-dimensional perovskite phase at the n-interface, suppressing the QFLS-VOC mismatch, and boosting the VOC. Concurrently, the use of an ionic interlayer or a self-assembled monolayer at the p-interface reduces the inferred field screening induced by mobile ions at JSC, promoting charge extraction and raising the JSC. The combination of the n- and p-type optimizations allows us to approach the thermodynamic potential of the perovskite absorber layer, resulting in 1 cm2 devices with performance parameters of VOCs up to 1.29 V, fill factors above 80% and JSCs up to 17 mA/cm2, in addition to a thermal stability T80 lifetime of more than 3500 h at 85 °C.

Chloride-Based Additive Engineering for Efficient and Stable Wide-Bandgap Perovskite Solar Cells.

Metal halide perovskite based tandem solar cells are promising to achieve power conversion efficiency beyond the theoretical limit of their single-junction counterparts. However, overcoming the significant open-circuit voltage deficit present in wide-bandgap perovskite solar cells remains a major hurdle for realizing efficient and stable perovskite tandem cells. Here, a holistic approach to overcoming challenges in 1.8 eV perovskite solar cells is reported by engineering the perovskite crystallization pathway by means of chloride additives. In conjunction with employing a self-assembled monolayer as the hole-transport layer, an open-circuit voltage of 1.25 V and a power conversion efficiency of 17.0% are achieved. The key role of methylammonium chloride addition is elucidated in facilitating the growth of a chloride-rich intermediate phase that directs crystallization of the desired cubic perovskite phase and induces more effective halide homogenization. The as-formed 1.8 eV perovskite demonstrates suppressed halide segregation and improved optoelectronic properties.