Parent–Child Cohesion, Basic Psychological Needs Satisfaction, and Emotional Adaptation in Left-Behind Children in China: An Indirect Effects Model

This study aimed to validate an indirect effects model of parent–child cohesion in emotional adaptation (i.e., loneliness and depression) via basic psychological needs satisfaction in Chinese left-behind children as well as the applicability of the model to both genders. A cross-sectional study was conducted and included 1,250 children aged between 9 and 12 years (635 left-behind children and 615 non-left-behind children) from rural primary schools. The results showed that: (1) relative to non-left-behind children, left-behind children exhibited significantly higher loneliness and depression scores and greater disadvantages involving father–child cohesion, mother–child cohesion, and psychological needs satisfaction. (2) Father– and mother–child cohesion were significantly negatively correlated with loneliness and depression and significantly positively correlated with psychological needs satisfaction in left-behind children. (3) Through structural equation modeling showed that psychological needs satisfaction partially mediated the relationship between parent–child cohesion and emotional outcomes in left-behind children. (4) Through multi-group analyses showed significant gender differences in structural weighting between parent–child cohesion and emotional adaptation, in that parent–child cohesion in left-behind boys was a stronger negative predictor of unfavorable emotional outcomes relative to that observed in left-behind girls, while psychological needs satisfaction in left-behind girls was a stronger negative predictor of unfavorable emotional outcomes relative to that observed in left-behind boys. The implications of these findings for interventions directed at Chinese left-behind children were discussed

Influence of the stoichiometry of tin-based 2D/3D perovskite active layers on solar cell performance

2D/3D mixed tin perovskites have the advantages of high crystallinity and preferential orientation compared to pure 3D tin perovskite. However, solar cells based on 2D/3D mixed tin perovskites are still limited by low power conversion efficiency (PCE) when compared to their lead-based counterparts. It is essential to gain deeper insight into the factors that limit the performance of these solar cells in order to further improve them. In this work, we demonstrate that the starting stoichiometry of 2D/3D (PEA(0.08)FA(x)SnI(3)) tin perovskite films influences their crystallization and photophysical properties as well as the solar cell performance. The reference 2D/3D film (x = 0.92, where x refers to the stoichiometry of the precursors) is highly crystalline with the 3D phase preferentially oriented and a small amount of 2D phase located at the bottom of the film. The reference solar cell delivers a PCE of about 8.0%. 2D/3D films with even higher FA concentration (x > 1.0) mainly consist of poorly crystalline and randomly oriented 3D phases, with much higher trap density compared to the reference film. The corresponding solar cells therefore suffer from severe trap-assisted charge recombination, and deliver a poor PCE o

Field-Effect Transistors Based on Formamidinium Tin Triiodide Perovskite

To date, there are no reports of 3D tin perovskite being used as a semiconducting channel in field-effect transistors (FETs). This is probably due to the large amount of trap states and high p-doping typical of this material. Here, the first top-gate bottom-contact FET using formamidinium tin triiodide perovskite films is reported as a semiconducting channel. These FET devices show a hole mobility of up to 0.21 cm(2) V-1 s(-1), an I-ON/OFF ratio of 10(4), and a relatively small threshold voltage (V-TH) of 2.8 V. Besides the device geometry, the key factor explaining this performance is the reduced doping level of the active layer. In fact, by adding a small amount of the 2D material in the 3D tin perovskite, the crystallinity of FASnI(3) is enhanced, and the trap density and hole carrier density are reduced by one order of magnitude. Importantly, these transistors show enhanced parameters after 20 months of storage in a N-2 atmosphere

Impact of the Hole Transport Layer on the Charge Extraction of Ruddlesden-Popper Perovskite Solar Cells

Recent works demonstrate that polyelectrolytes as a hole transport layer (HTL) offers superior performance in Ruddlesden-Popper perovskite solar cells (RPPSCs) compared to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The factors contributing to such improvement need to be systematically investigated. To achieve this, we have systematically investigated how the two HTLs affect the morphology, crystallinity, and orientation of the Ruddlesden-Popper perovskite (RPP) films as well as the charge extraction of the RPPSCs. PEDOT:PSS as a HTL leads to RPP films of low crystallinity and with a number of large pinholes. These factors lead to poor charge carrier extraction and significant charge recombination in the RPPSCs. Conversely, a PCP-Na HTL gives rise to highly crystalline and pinhole-free RPPSC films. Moreover, a PCP-Na HTL provides a better energy alignment at the perovskite/HTL interface because of its higher work function compared to PEDOT:PSS. Consequently, devices using PCP-Na as HTLs are more efficient in extracting charge carriers

Tuning the Energetic Landscape of Ruddlesden-Popper Perovskite Films for Efficient Solar Cells

Ruddlesden-Popper perovskite films deposited with different methods show very diverse phase segregation and composition. When DMSO is used as solvent, the conventional method based on spin-coating and annealing produces very poor devices, whereas the vacuum-assisted method proposed here allows obtaining devices with efficiency up to 14.14%. The conventional method gives rise to a three-dimensional (3D)-like phase on the top of the film but dominant n = 2 phase with large domains (∼40 μm) at the bottom of the film. These n = 2 domains are oriented with their inorganic slabs parallel to the substrate and inhibit the charge transport in the vertical direction. Consequently, severe monomolecular and bimolecular charge recombination occurs in the solar cells. Conversely, the vacuum-assisted method yields films with a 3D-like phase dominant throughout their entire thickness and only a small amount of n ≤ 2 domains of limited dimensions (∼3 μm) at the bottom, which facilitate charge transport and reduce charge recombination.</p

Enhancing the Performance of the Half Tin and Half Lead Perovskite Solar Cells by Suppression of the Bulk and Interfacial Charge Recombination

In this article it is investigated how the hole extraction layer (HEL) influence the charge recombination and performance in half tin and half lead (FASn(0.5)Pb(0.5)I(3)) based solar cells (HPSCs). FASn(0.5)Pb(0.5)I(3) film grown on PEDOT:PSS displays a large number of pin-holes and open grain boundaries, resulting in a high defect density and shunts in the perovskite film causing significant bulk and interfacial charge recombination in the HPSCs. By contrast, FASn(0.5)Pb(0.5)I(3) films grown on PCP-Na, an anionic conjugated polymer, show compact and pin-hole free morphology over a large area, which effectively eliminates the shunts and trap states. Moreover, PCP-Na is characterized by a higher work function, which determines a favorable energy alignment at the anode interface, enhancing the charge extraction. Consequently, both the interfacial and bulk charge recombination in devices using PCP-Na HEL are considerably reduced giving rise to an overall improvement of all the device parameters. The HPSCs fabricated with this HEL display power conversion efficiency up to 16.27%, which is 40% higher than the efficiency of the control devices using PEDOT:PSS HEL (11.60%). Furthermore, PCP-Na as HEL offers superior performance in larger area devices compared to PEDOT:PSS

Parent-child attachment and good behavior habits among Chinese children: Chain mediation effect of parental involvement and psychological Suzhi.

This study examines the mediation effect of parental involvement and psychological Suzhi between the relationship of parent-child attachment and good behavior habits in Chinese children. The participants comprised 563 children from four Chinese kindergartens (4.41±0.96) whose parents reported measures of parent-child attachment, parental involvement, psychological Suzhi, and good behavior habits in their children. The results indicated that (1) Parental attachment, parental involvement and psychological Suzhi were positively correlated with good behavior habits of young children; (2) Parental involvement and psychological Suzhi mediated the relationship between parent-child attachment and good behavior habits in children separately; (3) Parent-child attachment indirectly affected children's good behavior habits through the path of "parental involvement and psychological Suzhi.

Enhancing the crystallinity and perfecting the orientation of formamidinium tin iodide for highly efficient Sn-based perovskite solar cells

Low power conversion efficiency (PCE) and poor reproducibility are among the main challenges for tin-based perovskite solar cells (HPSCs). The facile formation of tin vacancies and oxidation of the divalent tin cation during the thin film fabrication process are among the causes of these problems, because the tin perovskite layer then becomes p-doped, resulting in significant trap-assisted recombination losses in devices. In this paper, we demonstrate that increasing the crystallinity of the tin perovskite film is an effective way to address the open issues with Sn-based perovskites. We succeed in improving the crystallinity of the 3D formamidinium tin iodide (FASnI(3)) grains, increasing their size, and perfecting their orientation in the out-of-plane direction by incorporating ethylammonium iodide (EAI) into a 2D/3D tin perovskite film (where 2D is PEA(2)FASn(2)I(7), PEA = phenylethylammonium). This leads to a decrease of traps and background charge carrier density, and therefore to decreased charge recombination losses in EA(x)2D/3D based devices, as compared not only to devices based on FASnI(3) but also to those based on 2D/3D mixtures. As a consequence, devices using a perovskite layer with composition EA(0.08)2D/3D exhibit much higher PCE (8.4%) and better reproducibility compared to devices based on mixed 2D/3D perovskites (7.7%) and 3D perovskite (4.7%)

Mechanism of Crystal Formation in Ruddlesden-Popper Sn-Based Perovskites

Knowledge of the mechanism of formation, orientation, and location of phases inside thin perovskite films is essential to optimize their optoelectronic properties. Among the most promising, low toxicity, lead-free perovskites, the tin-based ones are receiving much attention. Here, an extensive in situ and ex situ structural study is performed on the mechanism of crystallization from solution of 3D formamidinium tin iodide (FASnI(3)), 2D phenylethylammonium tin iodide (PEA(2)SnI(4)), and hybrid PEA(2)FA(n)(-1)Sn(n)I(3)(n)(+1) Ruddlesden-Popper perovskites. Addition of small amounts of low-dimensional component promotes oriented 3D-like crystallite growth in the top part of the film, together with an aligned quasi-2D bottom-rich phase. The sporadic bulk nucleation occurring in the pure 3D system is negligible in the pure 2D and in the hybrid systems with sufficiently high PEA content, where only surface crystallization occurs. Moreover, tin-based perovskites form through a direct conversion of a disordered precursor phase without forming ordered solvated intermediates and thus without the need of thermal annealing steps. The findings are used to explain the device performances over a wide range of composition and shed light onto the mechanism of the formation of one of the most promising Sn-based perovskites, providing opportunities to further improve the performances of these interesting Pb-free materials