Managing Interfacial Defects and Carriers by Synergistic Modulation of Functional Groups and Spatial Conformation for High-Performance Perovskite Photovoltaics Based on Vacuum Flash Method.

Interfacial nonradiative recombination loss is a huge barrier to advance the photovoltaic performance. Here, one effective interfacial defect and carrier dynamics management strategy by synergistic modulation of functional groups and spatial conformation of ammonium salt molecules is proposed. The surface treatment with 3-ammonium propionic acid iodide (3-APAI) does not form 2D perovskite passivation layer while the propylammonium ions and 5-aminopentanoic acid hydroiodide post-treatment lead to the formation of 2D perovskite passivation layers. Due to appropriate alkyl chain length, theoretical and experimental results manifest that COOH and NH3 + groups in 3-APAI molecules can form coordination bonding with undercoordinated Pb2+ and ionic bonding and hydrogen bonding with octahedron PbI6 4- , respectively, which makes both groups be simultaneously firmly anchored on the surface of perovskite films. This will strengthen defect passivation effect and improve interfacial carrier transport and transfer. The synergistic effect of functional groups and spatial conformation confers 3-APAI better defect passivation effect than 2D perovskite layers. The 3-APAI-modified device based on vacuum flash technology achieves an alluring peak efficiency of 24.72% (certified 23.68%), which is among highly efficient devices fabricated without antisolvents. Furthermore, the encapsulated 3-APAI-modified device degrades by less than 4% after 1400 h of continuous one sun illumination.

Heterojunction In Situ Constructed by a Novel Amino Acid-Based Organic Spacer for Efficient and Stable Perovskite Solar Cells.

The optical properties and stability of metal halide perovskites can be improved by reducing their dimensionality. Because defects at the perovskite film grain body and boundaries cause significant energetic losses by nonradiative recombination, perovskite films with manageable crystal size and macroscopic grains are essential to improve the photovoltaic properties. Through theoretical calculation models and experiments, we show that the carboxyl group of 4-ammonium butyric acid-based cation (4-ABA+) can interact with the three-dimensional (3D) perovskite to produce in situ a secondary grain growth by post-treatment. It passivates the trap defects and broadens the light absorption. 4-ABA+ could induce a 2D capping layer on top of 3D mixed cation-based perovskite to construct a 2D/3D heterojunction. The 4-ABA+-modified perovskite film consists of large-sized grains with extremely low trap state densities and possesses a longer charge carrier lifetime and good stability, resulting in efficient perovskite solar cells with a champion efficiency of 23.16% and a VOC of 1.20 V. We show that the 4-ABA+-treated devices outperform the 3-ammonium propionic acid (3-APA+)- and 5-ammonium valeric acid (5-AVA+)-treated ones. Moreover, the devices exhibit high stability under high humidity and continuous light soaking conditions. This work gives a hint that our approach based on 4-ABA+ treatment is key to achieving better electrical properties, a controlled crystal growth, and highly stable perovskite solar cells.

Stabilizing Perovskite Precursor by Synergy of Functional Groups for NiOx -Based Inverted Solar Cells with 23.5 % Efficiency.

Perovskite solar cells suffer from poor reproducibility due to the degradation of perovskite precursor solution. Herein, we report an effective precursor stabilization strategy via incorporating 3-hydrazinobenzoic acid (3-HBA) containing carboxyl (-COOH) and hydrazine (-NHNH2 ) functional groups as stabilizer. The oxidation of I- , deprotonation of organic cations and amine-cation reaction are the main causes of the degradation of mixed organic cation perovskite precursor solution. The -NHNH2 can reduce I2 defects back to I- and thus suppress the oxidation of I- , while the H+ generated by -COOH can inhibit the deprotonation of organic cations and subsequent amine-cation reaction. The above degradation reactions are simultaneously inhibited by the synergy of functional groups. The inverted device achieves an efficiency of 23.5 % (certified efficiency of 23.3 %) with an excellent operational stability, retaining 94 % of the initial efficiency after maximum power point tracking for 601 hours.

High-Performance CsPbIBr2 Perovskite Solar Cells: Effectively Promoted Crystal Growth by Antisolvent and Organic Ion Strategies.

Growing attention has been paid to CsPbIBr2 perovskite solar cells (PSCs) after balancing the band gap and stability features of the interested full-inorganic perovskites. However, their power-conversion efficiency (PCE) still lags behind that of the PSCs using hybrid halide perovskite and how to increase the corresponding PCE is still a challenge. Herein, antisolvents and organic ion surface passivation strategies were systematically applied to precisely control the growth of CsPbIBr2 crystals for constructing a high-quality full-inorganic perovskite film. Through careful adjustments, a CsPbIBr2 film with a pure phase, full coverage, and high crystallinity with preferable (100) orientation was successfully obtained by introducing diethyl ether as the antisolvent followed by guanidinium surface passivation. The optimal CsPbIBr2 film was composed by a large grain with an average size of 950 nm, few grain boundaries, and higher hydrophobic property. Planer PSC using the optimal CsPbIBr2 film and electron-beam-deposited TiO2 compact layer exhibits a PCE of 9.17%, which ranks among the highest PCE range of the reported CsPbIBr2 PSCs. Besides, the designed CsPbIBr2 PSC exhibited good long-term stability, which could maintain 90% of the initial PCE in 40% humidity ambient, which remained constant after heat treatment at 100 °C for 100 h. Based on the optimal CsPbIBr2 film, the flexible and large-area (up to 225 mm2) PSCs were further fabricated. The adopted film improvement methods were further extended to other kinds of full-organic PSCs, which demonstrated the universality of this strategy.

Efficient rare earth co-doped TiO2 electron transport layer for high-performance perovskite solar cells.

Perovskite solar cells (PSCs) had received great attention as a result of their recent rapid increasing efficiency. However, the stability of PSCs is still a challenge due to the degradation of the perovskite layer caused by the high-energy ultraviolet (UV) irradiation. Inspired by the luminescent down converting ability for UV blocking and conversion as well as energy transfer between suitable rare earth (RE) ions, a planar CH3NH3PbI3 perovskite solar cell using Sm3+ and Eu3+ co-doped TiO2 electron transfer layer was designed. By optimizing the Sm3+ and Eu3+ doping concentration, the REs co-doped TiO2 ETL combines the advantages of high electron extraction and lower interfacial recombination caused by REs introduction, a power conversion efficiency of 19.01% was obtained. In addition, benefit from the enhanced ability to convert UV light into visible light of the co-doped ETL, the PSCs can sustain higher than at least 80% of the original efficiency over 25 days of full sunlight irradiation or after 100 h of UV illumination. Moreover, since the low-temperature pulsed laser deposition was adopted in ETL fabrication process, the large area (225 mm2) and flexibility devices were further explored, with PCEs of 12.60% and 15.48%, respectively. This work indicates that Sm3+ and Eu3+ co-doped ETLs are effective and promising method to enhance the photovoltaic performance and UV stability of PSCs, which can be further applied in other PSCs with different ETLs and co-doping types.

Enhancing Photostability of Perovskite Solar Cells by Eu(TTA)2(Phen)MAA Interfacial Modification.

Organic-inorganic lead halide perovskite solar cells (PSCs) exhibit spectacular changes in the photovoltaic area, but they still face the challenges of full spectral utilization and photostability under continuous light irradiation. The ultraviolet (UV) part in sunlight could induce oxygen vacancy in the mesoporous TiO2 (m-TiO2) layer, resulting in the degradation of perovskite photoactive films and the rapidly decreased device performance. In this work, we demonstrate that an effective luminescent downconversion material, Eu(TTA)2(Phen)MAA (ETPM), can be used as an interfacial modifier between the m-TiO2 layer and the perovskite photoactive layer to improve the power conversion efficiency (PCE) from 17.00 to 19.07%. The improved device performance can be ascribed to the effective utilization of incident UV light and reduced carrier recombination. Meanwhile, the conversion of the UV light by ETPM could inhibit the stability loss of the device under irradiation. As a result, the modified PSCs can maintain 86% of their initial value under continuous light soaking for 100 h, higher than that of 40% for the control device. This work indicates that the introduction of the luminescent downconversion material ETPM can successfully improve the PCE and photostability of PSCs.

Sn-doped 3D ATO inverse opal/hematite hierarchical structures: facile fabrication and efficient photoelectrochemical performance.

The coupling of hematite with a three-dimensional (3D) conductive inverse opal (IO) skeleton provides an efficient route to enhance the photoelectrochemical (PEC) properties of hematite without changing its chemical composition. In this work, novel 3D antimony-doped SnO2 (ATO) IO/hematite heterostructures were facilely fabricated, and their PEC properties were thoroughly studied. Analysis of the morphologies and photocurrent densities of the 3D ATO IO//Fe2O3 heterostructures reveals that the high conductivity of the ATO skeleton as well as the high specific area and good light harvesting properties of the 3D IO structures greatly enhance their PEC performance. In particular, further morphology tuning by changing the diameters of the ATO IO skeletons could optimize the optical and electrical properties of the as-prepared heterostructures, demonstrating the important influence of morphology engineering on PEC performance. Moreover, after a simple Sn-doping process, the PEC properties of the as-prepared structure could be further enhanced; a photocurrent density of 1.28 mA cm-2 at 1.23 V vs. RHE was obtained under AM 1.5G illumination.

Enhanced Performance of Perovskite Solar Cells with Zinc Chloride Additives.

Perovskite solar cells (PSCs) have attracted extensive attention due to their impressive photovoltaic performance. The quality of the perovskite layer is very critical to achieve high device performance. Here, we explore the partial substitution of PbI2 by ZnCl2 in the preparation of CH3NH3PbI3 and its effects on perovskite morphology, optical properties, and photovoltaic performance. Consequently, the device with 3% ZnCl2 shows great improvement in power conversion efficiency (PCE) from 16.4 to 18.2% compared to that of the control device. Moreover, the device is more stable than the control device, with only 7% degradation after aging for 30 days. These results are attributed to the increased grain size, improved film morphology, and reduced recombination loss after the partial substitution of PbI2 by ZnCl2 in the perovskite film. This work develops a new approach for morphology control through rational additives in the perovskite film, and paves the way toward further enhancing the device performances of PSCs including PCE and stability.

Improved method of step length estimation based on inverted pendulum model.

Step length estimation is an important issue in areas such as gait analysis, sport training, or pedestrian localization. In this article, we estimate the step length of walking using a waist-worn wearable computer named eButton. Motion sensors within this device are used to record body movement from the trunk instead of extremities. Two signal-processing techniques are applied to our algorithm design. The direction cosine matrix transforms vertical acceleration from the device coordinates to the topocentric coordinates. The empirical mode decomposition is used to remove the zero- and first-order skew effects resulting from an integration process. Our experimental results show that our algorithm performs well in step length estimation. The effectiveness of the direction cosine matrix algorithm is improved from 1.69% to 3.56% while the walking speed increased.

SIFT-Based Indoor Localization for Older Adults Using Wearable Camera.

This paper presents an image-based indoor localization system for tracking older individuals' movement at home. In this system, images are acquired at a low frame rate by a miniature camera worn conveniently at the chest position. The correspondence between adjacent frames is first established by matching the SIFT (scale-invariant feature transform) based key points in a pair of images. The location changes of these points are then used to estimate the position of the wearer based on use of the pinhole camera model. A preliminary study conducted in an indoor environment indicates that the location of the wearer can be estimated with an adequate accuracy.

[Effects of dental health awareness and behaviours on the glycemic metabolic characteristics and periodontal disease of patients with type 2 diabetic].

OBJECTIVE: To analyze the effects of dental health awareness and behaviours on the relationship between glycemic metabolic characteristics and periodontal disease of type 2 diabetic patients. METHODS: In the study, 83 subjects with type 2 diabetes mellitus were recruited. The clinical periodontal indexes, such as pocket probing depth (PPD), attachment loss (AL), modified bleeding index (mBI), plaque index (PLI) were obtained with a Williams type periodontal probe; Laboratory examinations including glycosylated haemoglobin A1(HbA1C) were made, glucose assay tested, and the structured questionnaire interview conducted evaluationg the knowledge, attitude and practice (KAP) about periodontal health. RESULTS: The prevalence of moderate and severe periodontitis was 67.5%, compared with mild periodontitis, whose severities were affected by the higher level of HbA1C (≥8.0%) (OR 54.1-143.1), followed by using glycemic drug (OR=12.9-44.6), stress (OR=16.9-29.6), and the dissatisfaction with diabetic therapy (OR=16.9-18.0) et al. Meanwhile the attachment loss conditions were also correlated with the poor periodontal knowledge level(OR=3.4),older age(OR=1.1),and misjudgement of gingival inflammation (OR=13.3) et al. On the other hand, individuals with moderate and severe periodontitis, having bad teeth brushing effects and knowing about dental plaque inadequately, had a significantly higher risk for the poorly controlled glycemic results (HbA1C≥8.0%), and the OR was 8.61, 8.07, and 7.49 respectively. CONCLUSION: In patients with type 2 diabetes the severity of periodontal disease and the glycemic metabolic level (HbA1C) have a definite bidirectional adverse interrelationship, which is affected by the dental health awareness and behaviours.

[Periodontal health status assessed by community periodontal index and related factors in adult population of Beijing urban community].

OBJECTIVE: To investigate the periodontal health conditions by using community periodontal index (CPI) and analyze the effects of related risk factors. METHODS: By stratified random sampling procedure, a total of 1 183 subjects aged 35-74 were recruited from 13 neighbour community and accepted structured interview and periodontal examination. RESULTS: The percentage of edentulous jaws was 2.3% (27/1 183). For the remaining 1 156 people, the percentage of subject with a highest CPI scores of 0,1,2,3,4 were 0.3%, 0.2%, 46.3%, 31.9%, 21.3%, respectively. At the sextant and tooth level, the numbers of healthy, bleeding, calculus, shallow pocket, deep pocket and missing pocket were 0.26, 0.25, 3.56, 1.06, 0.39, 0.48, and 3.32, 2.02, 15.43, 2.60, 0.70, 3.93, respectively. By multivariable logistic regression models, many risk indicators such as age, gender, smoking, the knowledge, attitudes and practices (KAP) status, etc. were demonstrated to be related to the distribution of deeper and missing pockets. CONCLUSION: The adult periodontal conditions of urban community were serious and affected by some demographic and behavior risk factors. More than half (53.2%) of the examined subjects require complex periodontal treatments.

[Effect of community periodontal care intervention on periodontal health and glycemic control in type 2 diabetic patients with chronic periodontitis].

OBJECTIVE: To evaluate the effectiveness of community periodontal care intervention in type 2 diabetic patients with chronic periodontitis who participated in community non-communicable diseases management service. METHODS: The randomized controlled and blinded community trial with a duration of six months was designed to compare effects of "periodontal initial therapy" on group I(22 cases), of "professional mechanical tooth cleaning (PMTC), i.e. coronal scaling" on group II(19 cases)and of "non-clinical therapy" on the control group(25 cases). The clinical periodontal indexes, such as probing depth (PD), attachment loss (AL), modified bleeding index (mBI), plaque index (PLI) were obtained with a Williams type periodontal probe; Laboratory examinations including glycosylated haemoglobin A1(HbA1C), glucose assay, were conducted. RESULTS: The reductions of PD in groups I and II were 0.71 and 0.70 mm, respectively, which was more significant than in control group (0.20 mm); the reductions of AL in groups I, II, and control group were 0.86, 0.57, and 0.03 mm, respectively, which showed significance in all the three groups. The subjects of groups I and II had 0.56% and 1.01% reductions of HbA1C respectively, and the significance was observed in group II. In addition, the improvement of HbA1C values in group II was highly correlated with the decrease in gingivitis (r=0.51, P=0.03). CONCLUSION: The community periodontal care approaches implemented in the community health service centers have significantly improved periodontal health as well as reduced glycemic level, which could be regarded as basic health care strategies for the patients with diabetes.

Changing use and knowledge of fluoride toothpaste by schoolchildren, parents and schoolteachers in Beijing, China.

OBJECTIVE: To assess the oral hygiene practices, current use of and knowledge about fluoride toothpaste among schoolchildren, parents, and schoolteachers; to describe the attitudes of parents and schoolteachers in relation to improving schoolchildren's oral health. DESIGN: Cross-sectional study. PARTICIPANTS: 1,557 schoolchildren, 1,132 parents, and 352 schoolteachers were recruited by multistage stratified sampling procedure in a district of Beijing, China. METHODS: Self-completed questionnaire. RESULTS: The percentage of schoolchildren, parents, and schoolteachers who actually used fluoride toothpaste was 88%, 86%, and 87%, respectively, and 74-78% of the respondent groups brushed their teeth twice a day or more. 64% of schoolchildren, 73% of parents, and 74% of schoolteachers confirmed the caries preventive effect of fluoride toothpaste. Toothpaste recommended by oral health professional organisations was preferred by respondents - particularly by schoolchildren - when purchasing toothpaste (86%). 93% of parents and 56% of schoolteachers recognised their important role in promoting children's oral health; however, their lack of knowledge seemed to be a major obstacle in fulfilling this role. CONCLUSIONS: The use of fluoride toothpaste in Beijing appears to have increased during the past decade. In addition to mass communication comprehensive school-based oral health programmes are needed to continuously promote the use of fluoride toothpaste among schoolchildren.

[Prevalence and related factors of periodontitis in community-dwelling Chinese with diabetes].

OBJECTIVE: To evaluate the periodontal conditions in community-dwelling Chinese with diabetes and analyze some related factors. METHODS: A total of 90 (45- to 84- year-old) patients with diabetes, participating in community-based non-communicable diseases management system, were recruited in this study. The examination items on these patients included periodontal measurements performed by pocket probing depth (PPD), attachment loss (AL), sulcus bleeding index (SBI), plaque index (PLI), and blood sugar metabolic level surveillance, as well as structured questionnaire interview. RESULTS: The prevalence of periodontitis was 100%, while 37.1% was diagnosed as having mild periodontitis, 24.4% with moderate, and 38.5% with advanced periodontitis. The AL level in male was significantly higher than that in female. The periodontal destruction was highly correlated with HbA1C value and affected by some socio-behavior factors based on multinomial logistic model. CONCLUSIONS: There is a positive correlation between AL and HbA1C level, and AL and HbA1C should be measured regularly. The patients' periodontal inflammation needs effective control. Priority should be given to the low income population and those with little periodontal knowledge for behavior interventions.

[Evaluation of the public on the psychosocial effects of fluorosis].

OBJECTIVE: To explore the attitude of the public to the psychosocial effects of fluorosis through investigating the public in different areas. METHODS: Twenty typical fluorosis photos were selected and evaluated by the public in Xingtai, Beijing and Guangzhou, which included 101 dentists, 118 dental students, 103 college students in non-dental schools, 102 clerks and 92 leaders. Each evaluator was required to answer seven five-point questions according to each photo. RESULTS: The mean of the public evaluation was going up with the increase of Dean's Index (DI) score, ranging from 2.21 to 4.74, meanwhile, the prevalence of reporting that fluorosis would affect their psychosocial status also ascended. Less than 25% people reported that very mild fluorosis (DI < or = 1) would affect the psychosocial status of patients, and mild fluorosis (DI = 2) would affect 25% - 56%, while the prevalence would increase to 48% - 97% in severe fluorosis group (DI > or = 3). "Bivariate Correlation Analysis" showed that significant correlation existed in the evaluation of the public and the degree of fluorosis. The scores of dentists were significantly lower than those of dental students, college students in non-dental schools and clerks. The evaluation scores of the public in Xingtai were generally higher than those in Beijing and Guangzhou. CONCLUSIONS: Mild or less fluorosis could lead to little psychosocial effects.

[A survey of cognition and utilization of fluoride toothpaste and associated factors].

OBJECTIVE: To survey the situation of cognition and utilization of fluoride toothpaste and associated factors amongst elementary and middle school students in Haidian district, Beijing. METHODS: Sample of students was recruited by a multistage, stratified, and probability proportional to size sampling procedure. Self-administered structured questionnaires were used to collect information concerning the knowledge of, attitudes to and utilization of fluoride toothpaste and associated factors. A total of 1 557 students completed the questionnaire effectively. RESULTS: The percent age of students who used fluoride toothpaste when brushing their teeth were 87.8%. More than 60% of students knew that fluoride toothpaste could prevent dental caries by strengthening the out layer of tooth surface. 41.6% of the students doubted about the harmless of fluoride toothpaste even to be used properly. Advertisement was the main source of information about the fluoride toothpaste. CONCLUSIONS: The percentage of students using fluoride toothpaste was high and the majority of them knew that fluoride toothpaste could prevent caries. The oral health education programme concerning the optimal use of fluoride in dental caries prevention is highly recommended.

[Evaluation of the psychosocial status of fluorosis patients in fluorosis epidemic areas].

OBJECTIVE: To explore the psychosocial effect of fluorosis on patients in fluorosis epidemic areas. METHODS: Multistage, stratified, clustered and random sampling method was used in this survey. Totally 416 inhabitants of 12, 15 and 35-44 years of age from rural fluorosis epidemic areas in Hebei province were selected. Dental fluorosis was classified by Dean's index (DI). A total of 178 patients with different types of fluorosis were involved in a psychosocial questionnaire investigation which included six five-point subscales, including attitude to teeth, subjective well-being, life satisfaction, interpersonal or social anxiety, effect of self-esteem, impact on behavior. RESULTS: Fluorosis prevalence in fluorosis epidemic areas of Xingtai in Hebei province was 71.20%, and significant difference existed among three age groups (Pearson Chi-square value = 167.51, P < 0.01). With the increase of DI score, the average value of subscale "attitude to teeth" rising, ranging from 2.58 to 3.51, and value of "subjective well-being" was also increasing, ranging from 2.35 to 2.9. Statistical difference of subscale average value was found only in these two subscales ("attitude to teeth": F = 4.787, P < 0.01; "subjective well-being": F = 2.538, P < 0.05). "Attitude to teeth" was significantly different between control group and moderate group (F = 0.52, P < 0.01) and between control group and severe group (F = 0.72, P < 0.01). While significant difference of "subjective well-being" could only be found between control group and severe group (F = 0.56, P < 0.01). According to the bivariate correlation analysis, strong correlation could be found between the degree of fluorosis and the average value of sub-scales. CONCLUSIONS: The psychosocial impact of fluorosis on patients in fluorosis epidemic areas mainly appeared in two aspects, i.e. attitude to teeth and the perception of well-being, especially in severe group.