Lead Isolation and Capture in Perovskite Photovoltaics toward Eco-Friendly Commercialization.

Perovskite solar cells (PSCs) are developed rapidly in efficiency and stability in recent years, which can compete with silicon solar cells. However, an important obstacle to the commercialization of PSCs is the toxicity of lead ions (Pb2+) from water-soluble perovskites. The entry of free Pb2+ into organisms can cause severe harm to humans, such as blood lead poisoning, organ failure, etc. Therefore, this work reports a "lead isolation-capture" dual detoxification strategy with calcium disodium edetate (EDTA Na-Ca), which can inhibit lead leakage from PSCs under extreme conditions. More importantly, leaked lead exists in a nontoxic aggregation state chelated by EDTA. For the first time, in vivo experiments are conducted in mice to systematically prove that this material has a significant inhibitory effect on the toxicity of perovskites. In addition, this strategy can further enhance device performance, enabling the optimized devices to achieve an impressive power conversion efficiency (PCE) of 25.19%. This innovative strategy is a major breakthrough in the research on the prevention of lead toxicity in PSCs.

Photochemical Shield Enabling Highly Efficient Perovskite Photovoltaics.

Oxygen is difficult to be physically removed. Oxygen will be excited by light to form free radicals which further attack the lattice of perovskite. The stabilization of α-FAPbI3 against δ-FAPbI3 is the key to optimize perovskite solar cells. Herein, the simple molecule, benzaldehyde (BAH) is adopted. The photochemical shield will be established in perovskite layer. Moreover, heterogeneous nucleation induced by BAH enhances the crystallization of α-FAPbI3. Consequently, the stability of device is improved significantly. The target device maintains 95% of original power conversion efficiency after 1500 h under air conditions and light-emitting diode light. The power conversion efficiency increases from 23.21% of pristine device to 24.82% of target device.

Magnetic-biased chiral molecules enabling highly oriented photovoltaic perovskites.

The interaction between sites A, B and X with passivation molecules is restricted when the conventional passivation strategy is applied in perovskite (ABX3) photovoltaics. Fortunately, the revolving A-site presents an opportunity to strengthen this interaction by utilizing an external field. Herein, we propose a novel approach to achieving an ordered magnetic dipole moment, which is regulated by a magnetic field via the coupling effect between the chiral passivation molecule and the A-site (formamidine ion) in perovskites. This strategy can increase the molecular interaction energy by approximately four times and ensure a well-ordered molecular arrangement. The quality of the deposited perovskite film is significantly optimized with inhibited nonradiative recombination. It manages to reduce the open-circuit voltage loss of photovoltaic devices to 360 mV and increase the power conversion efficiency to 25.22%. This finding provides a new insight into the exploration of A-sites in perovskites and offers a novel route to improving the device performance of perovskite photovoltaics.

Characterizing Spatial and Energetic Distributions of Trap States Toward Highly Efficient Perovskite Photovoltaics.

Due to their greater opt electric performance, perovskite photovoltaics (PVs) present huge potential to be commercialized. Perovskite PV's high theoretical efficiency expands the available development area. The passivation of defects in perovskite films is crucial for approaching the theoretical limit. In addition to creating efficient passivation techniques, it is essential to direct the passivation approach by getting precise and real-time information on the trap states through measurements. Therefore, it is necessary to establish quantitative characterization methods for the trap states in energy and 3D spaces. The authors cover the characterization of the spatial and energy distributions of trap states in this article with an eye toward high-efficiency perovskite photovoltaics. After going over the strategies that have been created for characterizing and evaluating trap states, the authors will concentrate on how to direct the creative development of characterization techniques for trap states assessment and highlight the opportunities and challenges of future development. The 3D space and energy distribution mappings of trap states are anticipated to be realized. The review will give key guiding importance for further approaching the theoretical efficiency of perovskite photovoltaics, offering some future research direction and technological assistance for the development of appropriate targeted passivation technologies.

Buried Interface Passivation: A Key Strategy to Breakthrough the Efficiency of Perovskite Photovoltaics.

Owing to the merits of low cost and high power conversion efficiency (PCE), perovskite solar cells (PSCs) have become the best candidate to replace the commonly used silicon solar cells. However, PSCs have been slow to enter the market for a number of reasons, including poor stability, high toxicity, and rigorous preparation process. Passivation strategies including surface passivation and bulk passivation have been successfully applied to improve the device performance of PSCs. The passivation of the defects at the buried interface, which is regarded as a key strategy to breakthrough the device efficiency and stability of PSCs in the future, is ongoing with challenge. Herein, in detail the recent passivation of the buried interface is introduced from three aspects: perovskite layer, buried interlayer, and transport layer. The passivation effect of the buried interface is clearly demonstrated through three categories of salts, organics, and 2D materials. In addition, the transport layer is classified into electron transport layer (ETL) and hole transport layer (HTL). These classifications can help to have a clear understanding of substances which generate passivating effect and guide the continuous promotion of the follow-up buried interface passivating work.

Low-Dimensional Phase Regulation to Restrain Non-Radiative Recombination for Sky-Blue Perovskite LEDs with EQE Exceeding 15 .

Achieving efficient blue electroluminescence (EL) remains the fundamental challenge that impedes perovskite light-emitting diodes (PeLEDs) towards commercial applications. The bottleneck accounting for the inefficient blue PeLEDs is broadly attributed to the poor-emissive blue perovskite emitters based on either mixed halide engineering or reduced-dimensional strategy. Herein, we report the high-performing sky-blue PeLEDs (490 nm) with the maximum EQE exceeding 15 % by incorporating a molecular modifier, namely 4,4'-Difluorophenone, for significantly suppressing the non-radiative recombination and tuning of the low-dimensional phase distribution of quasi-2D blue perovskites, which represents a remarkable paradigm for developing the new generation of blue lighting sources.

Doping Strategies for Promising Organic-Inorganic Halide Perovskites.

Organic-inorganic halide perovskites (OIHPs) obtained tremendous attention due to their low cost and excellent properties. However, the stability and toxicity of Pb-based OIHPs (POIHPs), as well as the weakness of efficiency and stability in Sn-based OIHPs (SOIHPs), are still serious issues for commercial application. Notably, composition engineering is an effective and direct strategy for improving these issues along with the control and modification of properties. Recently, the doping strategies for POIHPs and SOIHPs are booming. Based on the relationship between properties and composition, the doping strategies for POIHPs and SOIHPs, aiming to provide a comprehensive review and guidance for the research are systematically summarized. Moreover, the doping strategies for Pb-Sn mixed OIHPs are also discussed. Finally, a brief perspective and conclusion toward future possible doping schemes and properties designment of POIHPs and SOIHPs are offered.

Light-Triggered Sustainable Defect-Passivation for Stable Perovskite Photovoltaics.

The generation of photoinduced defects and freely moving halogen ions is dynamically updated in real time. Accordingly, most reported strategies are static and short-term, which make their improvements in photostability very limited. Therefore, seeking new passivation strategies to match the dynamic characteristics of defect generation is very urgent. Without newly generated defects, a passivation molecule should exist in the configuration that would not become the initiation sites for defect generation. With newly generated defects, the passivation molecule should transfer into the other configuration that possesses the passivation sites. Herein, a classical photoisomeric molecule, spiropyran, is adopted, whose pre- and post-isomeric forms meet the requirements for two different configurations, to realize the state transition once the photoinduced defects appear during subsequent operation and dynamic capture for continuous renewal of defects. Consequently, spiropyrans work as light-triggered and self-healing sustainable passivation sites to realize continuous defect repair. The target devices retain 93% and 99% of their initial power conversion efficiencies after 456 h aging under ultraviolet illumination and 1200 h aging under full-spectrum illumination, respectively. This work provides a novel concept of sustainable passivation strategy to realize continuous defect-passivation and film-healing in perovskite photovoltaics.

Visualizing the Surface Photocurrent Distribution in Perovskite Photovoltaics.

Defect states play an important role in the photovoltaic performance of metal halide perovskites. Particularly, the passivation of surface defects has made great contributions to high-performance perovskite photovoltaics. This highlights the importance of understanding the surface defects from a fundamental level by developing more accurate and operando characterization techniques. Herein, a strategy to enable the surface carriers and photocurrent distributions on perovskite films to be visualized in the horizontal direction is put forward. The visual image of photocurrent distribution is realized by combining the static local distribution of carriers provided by scanning near-field optical microscopy with the dynamic transporting of carriers achieved via a scanning photocurrent measurement system. Taking a surface passivated molecule as an example, a comprehensive defect scene including static and dynamic as well as local and entire conditions is obtained using this strategy. The comprehensive analysis of the trap states in perovskite films is pioneered vertically and horizontally, which will powerfully promote the deep understanding of defect mechanisms and carrier behavior for the goal of fabricating high-performance perovskite optoelectronic devices.

Full-Dimensional Grain Boundary Stress Release for Flexible Perovskite Indoor Photovoltaics.

Perovskite photovoltaics are strong potential candidates to drive low-power off-grid electronics for indoor applications. Compared with rigid devices, flexible perovskite devices can provide a more suitable surface for indoor small electronic devices, enabling them have a broader indoor application prospect. However, the mechanical stability of flexible perovskite photovoltaics is an urgent issue solved. Herein, a kind of 3D crosslinking agent named borax is selected to carry out grain boundary penetration treatment on perovskite film to realize full-dimensional stress release. This strategy improves the mechanical and phase stabilities of perovskite films subjected to external forces or large temperature changes. The fabricated perovskite photovoltaics deliver a champion power conversion efficiency (PCE) of 21.63% under AM 1.5G illumination, which is the highest one to date. The merit of low trap states under weak light makes the devices present a superior indoor PCE of 31.85% under 1062 lux (LED, 2956 K), which is currently the best flexible perovskite indoor photovoltaic device. This work provides a full-dimensional grain boundary stress release strategy for highly stable flexible perovskite indoor photovoltaics.

Physical Fields Manipulation for High-Performance Perovskite Photovoltaics.

With the efforts of researchers from all over the world, metal halide perovskite solar cells (PSCs) have been booming rapidly in recent years. Generally, perovskite films are sensitive to surrounding conditions and will be changed under the action of physical fields, resulting in lattice distortion, degradation, ion migration, and so on. In this review, the progress of physical fields manipulation in PSCs, including the electric field, magnetic field, light field, stress field, and thermal field are reviewed. On this basis, the influences of these fields on PSCs are summarized and prospected. Finally, challenges and prospective research directions on how to make better use of external-fields while minimizing the unnecessary and disruptive impacts on commercial PSCs with high-efficiency and steady output are proposed.

Perovskite indoor photovoltaics: opportunity and challenges.

With the rapid development of the Internet of Things (IoTs), photovoltaics (PVs) has a vast market supply gap of billion dollars. Moreover, it also puts forward new requirements for the development of indoor photovoltaic devices (IPVs). In recent years, PVs represented by organic photovoltaic cells (OPVs), silicon solar cells, dye-sensitized solar cells (DSSCs), etc. considered for use in IoTs mechanisms have also been extensively investigated. However, there are few reports on the indoor applications of perovskite devices, even though it has the advantages of better performance. In fact, perovskite has the advantages of better bandgap adjustability, lower cost, and easier preparation of large-area on flexible substrates, compared with other types of IPVs. This review starts from the development status of IoTs and investigates the cost, technology, and future trends of IPVs. We believe that perovskite photovoltaics is more suitable for indoor applications and review some strategies for fabricating high-performance perovskite indoor photovoltaic devices (IPVs). Finally, we also put forward a perspective for the long-term development of perovskite IPVs.

CsPbBrI2 perovskites with low energy loss for high-performance indoor and outdoor photovoltaics.

Over the years, the efficiency of inorganic perovskite solar cells (PSCs) has increased at an unprecedented pace. However, energy loss in the device has limited a further increase in efficiency and commercialization. In this work, we used (NH4)2C2O4·H2O to treat CsPbBrI2 perovskite film during spin-coating. The CsPbBrI2 underwent secondary crystallization to form high quality films with micrometer-scale and low trap density. (NH4)2C2O4·H2O treatment promoted charge transfer capacity and reduced the ideal factor. It also dropped the energy loss from 0.80 to 0.64 eV. The resulting device delivered a power conversion efficiency (PCE) of 16.55% with an open-circuit voltage (Voc) of 1.24 V, which are largely improved compared with the reference device which exhibited a PCE of 13.27% and a Voc of 1.10 V. In addition, the optimized treated device presented a record indoor PCE of 28.48% under a fluorescent lamp of 1000 lux, better than that of the reference device (19.05%).

Perovskite Films with Reduced Interfacial Strains via a Molecular-Level Flexible Interlayer for Photovoltaic Application.

Interface strains and lattice distortion are inevitable issues during perovskite crystallization. Silane as a coupling agent is a popular connector to enhance the compatibility between inorganic and organic materials in semiconductor devices. Herein, a protonated amine silane coupling agent (PASCA-Br) interlayer between TiO2 and perovskite layers is adopted to directionally grasp both of them by forming the structural component of a lattice unit. The pillowy alkyl ammonium bromide terminals at the upper side of the interlayer provide well-matched growth sites for the perovskite, leading to mitigated interface strain and ensuing lattice distortion; meanwhile, its superior chemical compatibility presents an ideal effect on healing the under-coordinated Pb atoms and halogen vacancies of bare perovskite crystals. The PASCA-Br interlayer also serves as a mechanical buffer layer, inducing less cracked perovskite film when bending. The developed molecular-level flexible interlayer provides a promising interfacial engineering for perovskite solar cells and their flexible application.

Aqueous-solution-processable metal oxides for high-performance organic and perovskite solar cells.

Poly(3,4-ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is a widely utilized hole-transporting material (HTM) in planar photovoltaic devices, such as organic solar cells (OSCs) and perovskite solar cells (PSCs). However, the hygroscopic nature of PEDOT:PSS aqueous dispersions may restrict their future application. Therefore, it is necessary to develop other effective and stable HTMs to achieve high-performance photovoltaic devices. Herein, we demonstrate a facile route to deposit solution-processed MoO3, GeO2, V2O5 and CrO3 thin films as hole-transporting layers by directly dissolving their commercial powders in deionized water. Among these, the solution-processed V2O5 (sV2O5) film exhibited the highest work function of 5.2 eV, and the best hydrophobicity, with a contact angle of 77.2°. The sV2O5-based OSCs and PSCs presented power conversion efficiencies (PCEs) of 8.36% and 14.13%, respectively. Notably, the PEDOT:PSS V2O5 composite HTM based device obtained a maximum PCE of 18.03% with a Voc exceeding 1.0 V. These aqueous-solution-processed HTMs have potential applications in green and low-cost photovoltaic devices by virtue of their simple and ecofriendly preparations.

[MicroRNA-16 regulates the proliferation, invasion and apoptosis of ovarian epithelial carcinoma cells in vitro].

OBJECTIVE: To study the role and mechanism of microRNA-16 (miR-16) in the proliferation, invasion and apoptosis of ovarian epithelial carcinoma cells in vitro. METHODS: The SKOV-3 cells were transfected with miR-16 mimics or negative control RNA (NC) by lipofectamine 2000. The expression of miR-16 was detected by real-time reverse transcription (RT)-PCR in SKOV-3 cells, and western blot was used to detect the expression of vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2) and bcl-2 protein. Methyl thiazolyl tetrazolium (MTT), 5-ethynyl-2'-deoxyuridine (EdU) and transwell assay were used to determine the proliferation and invasion abilities. And the rate of apoptotic cell was detected by flow cytometry method. RESULTS: (1) The expression level of miR-16 in the transfection cells group was significantly higher than that in NC group (125.93 ± 15.30 versus 0.78 ± 0.16, P < 0.01). (2) The relative expression level of VEGF protein in transfection cells, NC and blank control group was 0.58 ± 0.05, 1.22 ± 0.03, 1.20 ± 0.03, MMP-2 protein was 0.63 ± 0.03, 1.16 ± 0.03, 1.21 ± 0.03, and bcl-2 protein 0.52 ± 0.03, 1.19 ± 0.05, 1.28 ± 0.06, respectively. The level of VEGF, MMP-2 and bcl-2 protein in the transfection group were lower than those in other control groups, and there were significantly differences among them (all P < 0.01). (3) After transfected 4 days, the inhibition rate of cell proliferation in the transfection group was dramatically higher than that in NC group [(37.2 ± 6.2)% versus (3.6 ± 3.2)%, P = 0.001]. (4) The percentage rate of proliferative cells in the transfection, NC and blank control group was (12.3 ± 0.8)%, (23.4 ± 1.8)%, (31.1 ± 4.9)%. And it was lower in the transfection group (P < 0.05). (5) Decreased cells via the transwell member in the transfection group (6 ± 3) were detected as compared with NC group (40 ± 9) and blank control group (48 ± 8, P < 0.01). (6) Twenty-four hours after cultured in serum starvation and hypoxia, the rate of the viable and late apoptotic cells in the transfection group were significantly higher than those in NC group and blank control group [the rate of viable apoptotic cell was (16.9 ± 2.1)%, (10.3 ± 1.7)% and (9.0 ± 0.8)% respectively, P < 0.01; the rate of late apoptotic cell was (13.4 ± 3.3)%, (3.2 ± 1.8)% and (0.7 ± 0.6)% respectively, P < 0.01]. After cultured 48 hours, total apoptotic cells in the transfection group was significantly more than those in other groups (P < 0.01). CONCLUSION: miR-16 might inhibit the proliferation, invasion of ovarian epithelial carcinoma cells and enhance their sensitivity to apoptotic stimuli via downregulation of the expression of VEGF, MMP-2 and bcl-2 protein.

[Role of microRNA-21 in the proliferation and apoptosis of ovarian epithelial carcinoma cells].

OBJECTIVE: To investigate the role and mechanism of microRNA-21(miR-21) in the proliferation and apoptosis of ovarian epithelial carcinoma cells. METHODS: A short-hairpin RNA specifically targeting miR-21 plasmid was constructed, and the recombinant was identified by restriction endonuclease analysis and DNA sequencing. Three experimental groups were included, transfection group (transfected with pSIREN-miR-21), negative control group (transfected with pSIREN-miR-21-neg) and blank control group (without transfection plasmid). The expression of miR-21 was detected by stem-loop real-time reverse transcription (RT)-PCR in OVCAR3 cells, and western blot was used to detect the expression of programmed cell death 4 (PDCD4) protein. Tethyl thiazolyl tetrazolium(MTT) and flow cytometry method were used respectively. RESULTS: Recombinant plasmid (pSIREN-miR-21) was constructed successfully and identified by restriction endonuclease analysis and DNA sequencing. The relative expression level of miR-21 in cells transfection, negative control and blank control group was 0.26 ± 0.08, 1.26 ± 0.21 and 1.00 respectively. The level of miR-21 in the cells in transfection group was significantly lower than those in the negative control and blank control group (P < 0.01). The gray scale of PDCD4 protein was 1443 ± 33, 858 ± 19 and 846 ± 16 in the transfection group, negative control and blank control group respectively. The value of PDCD4 in transfection group was higher than other control groups, and there were significantly difference among them(P < 0.01). Moreover, the optical density of the cells in transfection group was 0.661 ± 0.015, significantly lower than those in two control groups (0.848 ± 0.150 for negative control, 0.935 ± 0.133 for blank control, P < 0.01). Forty-eight hours after transfection, the rate of viable apoptotic cell was significantly higher than negative control and blank control group [(25.821 ± 0.763)% vs. (0.010 ± 0.003)% vs. (0.238 ± 0.023)%; P < 0.01]; 72 hours after transfection, the rates of viable apoptotic cell and necrotic cell were all higher than the two control groups [the rate of viable apoptotic cell was (30.480 ± 0.821)%, (7.792 ± 0.312)% and (7.033 ± 0.257)% respectively (P < 0.01); the rate of necrotic cell was (3.558 ± 0.211)%, (1.557 ± 0.067)% and (1.049 ± 0.028)%, respectively (P < 0.01)]. CONCLUSION: miR-21 might play an important role in the proliferation and apoptosis of ovarian epithelial carcinoma cells through negatively control the expression of PDCD4.

[Expression of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 in human and nude mouse ectopic endometrium and the effect of estrogen and progestin on their expression].

OBJECTIVE: To explore the roles of matrix metalloproteinase-1(MMP-1) and tissue inhibitor of metalloproteinase-1(TIMP-1) in the pathogenesis of endometriosis and the effects of estrogen and progestin on their expression. METHODS: Immunohistochemistry and RT-PCR were employed to detect the expression of MMP-1 and TIMP-1 in the ectopic tissues of 35 patients with endometriosis, 22 eutopic endometrium tissues from women with endometriosis and 28 normal controls. Fifty-nine nude mice were injected with human late secretory endometrial chippings and randomized into estrogen group, progestin group, estrogen-progestin group and control group with corresponding treatments. The implantation rates and graft morphology were observed and MMP-1 and TIMP-1 expressions in the grafts detected by immunohistochemistry. RESULTS: Typical endometrial glands and stroma were observed in all the groups with comparable implantation rates. The administration of progestin was associated with multiple peritoneal implantation sites and significantly larger implants. The transplanted endometria showed proliferative or secretory changes with estrogen or progestin administration. MMP-1 expression significantly increased and TIMP-1 expression decreased with increased MMP-1/TIMP-1 ratio in human and nude mouse ectopic endometria in comparison with those in normal endometria (P<0.05, P<0.01). MMP-1 expression was higher in estrogen and estrogen-progestin groups than in the control group, and was lower in the 3 sexual hormone-treated groups than in the control group. MMP-1 mRNA expression in the eutopic endometrium was significantly higher than that in the normal endometria. CONCLUSION: Progestrin can not inhibit MMP-1 expression or the effect of estrogen on ectopic endometrium known as progestin resistance. The high expression of MMP-1 and low expression of TIMP-1 in endometriotic tissues confer strong invasiveness of ectopic endometrial tissue, especially in eutopic endometrial tissue, and may play an important role in the pathogenesis of endometriosis.

[Expression of microRNA-21 in ovarian epithelial carcinoma and its clinical significance].

OBJECTIVE: To investigate the expression of microRNA-21(miR-21) in ovarian epithelial carcinoma and its association with the clinicopathological features. METHODS: The expression of miR-21 was detected by Stem-loop real-time RT-PCR in 48 cases of ovarian epithelial carcinomas, 24 cases of benign ovarian epithelial tumors and 15 cases of normal ovarian tissues. RESULTS: The relative expression level of miR-21(2-(DeltaDelta)CT) was 4.849-/+1.813 in the ovarian epithelial carcinomas, significantly higher than that in the benign ovarian tumors and normal ovarian tissues (P<0.01), but comparable between the latter two groups. The expression of miR-21 was not correlated to the histological type, but increased significantly with the progression of the clinical stages and histological grading (P<0.01), showing a close correlation to lymphatic metastasis. CONCLUSION: MiR-21 might play a role as an oncogene in the tumorigenesis and development of ovarian epithelial carcinoma, and is possibly correlated to the progression and prognosis of ovarian epithelial carcinoma.

[Expression of matrix metalloproteinase-9 and tumor necrosis factor-alpha in the placenta of patients with pregnancy-induced hypertension].

OBJECTIVE: To investigate the role of matrix metalloproteinase-9 (MMP-9) and tumor necrosis factor-alpha (TNF-alpha) in the pathogenesis of pregnancy-induced hypertension (PIH). METHODS: The placenta samples were collected from 57 patients with PIH and 24 normal pregnant women. Immunohistochemical staining was used to examine positive expression of MMP-9 and TNF-alpha in these samples. RESULTS: The positive expression of MMP-9 in the normal group was significantly higher than that in patients with moderate or severe PIH (P<0.01), while no significant difference was found between normal pregnant women and patients with mild PIH (P>0.05), and expression decreased drastically with the progression of PIH (P<0.05). The expression of TNF-alpha in the patients with mild, moderate and severe PIH groups were significantly higher than that in the normal group (P<0.05, P<0.01 and P<0.01, respectively), and the differences were also significant between the PIH groups of different severities (P<0.01). No correlation was found between MMP-9 and TNF-alpha expressions in the normal and mild PIH groups (r=0.287, P>0.05; r=0.382, P>0.05), in the patients with moderate and severe PIH, MMP-9 expression showed inverse correlation with TNF-alpha expression (r=-0.563, P<0.05; r=-0.681, P<0.01). CONCLUSION: Lowerd MMP-9 expression in syncytiotrophoblast might result in defective nidation in the placenta where local ischemia and hypoxia cause abnormal TNF-alpha elevation, which might be one of the important factors inducing PIH.