Formamidinium (FA) based perovskites are considered as one of the most promising light‐absorbing perovskite materials owing to their narrower band gap and better thermal stability compared to ...conventional methylammonium‐based perovskites. Constant improvement by using various additives stimulates the potential application of these perovskites. Amine molecules with different structures have been widely used as typical additives in FA‐based perovskite solar cells, and decent performances have been achieved. Thus, a systematic review focusing on structural regulation and functional construction of amines in FA‐based perovskites is of significance. Herein, we analyze the construction mechanism of different structural amines on the functional perovskite crystals. The influence of amine molecules on specific perovskite properties including defect conditions, charge transfer, and moisture resistance are evaluated. Finally, we summarize the design rules of amine molecules for the application in high‐performance FA‐based perovskites and propose directions for the future development of additive molecules.
The structural design of amine molecules is effective for functional construction of perovskite light‐absorbing layer in perovskite solar cells. High‐efficiency and robust perovskite solar cells can be achieved through crystal regulation of formamidinium‐based perovskites and improvement of the specific perovskite properties including defect condition, charge transfer, and moisture resistance.
Three‐dimensional (3D) metal‐halide perovskite solar cells (PSCs) have demonstrated exceptional high efficiency. However, instability of the 3D perovskite is the main challenge for industrialization. ...Incorporation of some long organic cations into perovskite crystal to terminate the lattice, and function as moisture and oxygen passivation layer and ion migration blocking layer, is proven to be an effective method to enhance the perovskite stability. Unfortunately, this method typically sacrifices charge‐carrier extraction efficiency of the perovskites. Even in 2D–3D vertically aligned heterostructures, a spread of bandgaps in the 2D due to varying degrees of quantum confinement also results in charge‐carrier localization and carrier mobility reduction. A trade‐off between the power conversion efficiency and stability is made. Here, by introducing 2D C6H18N2O2PbI4 (EDBEPbI4) microcrystals into the precursor solution, the grain boundaries of the deposited 3D perovskite film are vertically passivated with phase pure 2D perovskite. The phases pure (inorganic layer number n = 1) 2D perovskite can minimize photogenerated charge‐carrier localization in the low‐dimensional perovskite. The dominant vertical alignment does not affect charge‐carrier extraction. Therefore, high‐efficiency (21.06%) and ultrastable (retain 90% of the initial efficiency after 3000 h in air) planar PSCs are demonstrated with these 2D–3D mixtures.
High‐efficiency (21.06%) and durable 2D–3D vertical aligned perovskite solar cells (PSCs) with phase pure 2D perovskite are demonstrated. The phase pure 2D perovskite minimizes photo‐generated charge‐carrier localization in the low‐dimensional perovskite; the dominant vertical alignment does not affect charge‐carrier extraction. The traditional constraint of trade‐off between efficiency and stability in PSC is overcome.
Organic light emitting diodes (OLEDs) employing organic thin‐film based emitters have attracted tremendous attention due to their widespread applications in lighting and as displays in mobile devices ...and televisions. The novel thin‐film photovoltaic techniques using organic or organic–inorganic hybrid materials such as organic photovoltaics (OPVs) and perovskite solar cells (PSCs) have become emerging competitive candidates with regard to the traditional photovoltaic techniques on account of high‐efficiency, low‐cost, and simple manufacturing processing properties. However, OLEDs, OPVs, and PSCs are vulnerable to the undesired degradation induced by moisture and oxygen. To afford long‐term stability, a robust encapsulation technique by employing materials and structures that possess high barrier performance against oxygen and moisture must be explored and employed to protect these devices. Herein, the recent progress on specific encapsulation materials and techniques for three types of devices on the basis of fundamental understanding of device stability is reviewed. First, their degradation mechanisms, as well as, influencing factors are discussed. Then, the encapsulation technologies and materials are classified and discussed. Moreover, the advantages and disadvantages of various encapsulation technologies and materials coupled with their encapsulation applications in different devices are compared. Finally, the ongoing challenges and future perspectives of encapsulation frontier are provided.
Thin‐film, cover, and hybrid encapsulation technologies, that function as a moisture and oxygen permeation barrier and mechanical protection to prevent leakage of toxic by‐product, and limit decomposition of reactants in a confined space, can be applied in organic light emitting diodes, organic and perovskite solar cells, leading to robust stability and long lifetime in three types of devices.
Optoelectronic synaptic devices have been attracting increasing attention due to their critical role in the development of neuromorphic computing based on optoelectronic integration. Here we start ...with silicon nanomembrane (Si NM) to fabricate optoelectronic synaptic devices. Organolead halide perovskite (MAPbI3) is exploited to form a hybrid structure with Si NM. We demonstrate that synaptic transistors based on the hybrid structure are very sensitive to optical stimulation with low energy consumption. Synaptic functionalities such as excitatory post-synaptic current (EPSC), paired-pulse facilitation, and transition from short-term memory to long-term memory (LTM) are all successfully mimicked by using these optically stimulated synaptic transistors. The backgate-enabled tunability of the EPSC of these devices further leads to the LTM-based mimicking of visual learning and memory processes under different mood states. This work contributes to the development of Si-based optoelectronic synaptic devices for neuromorphic computing.
Perovskite solar cells (PSCs) are a promising third‐generation photovoltaic (PV) technology developed rapidly in recent years. Further improvement of their power conversion efficiency is focusing on ...reducing the non‐radiative charge recombination induced by the defects in metal halide perovskites. So far, defect passivation by the organic small molecule has been considered as a promising approach for boosting the PSC performance owing to their large structure flexibility adapting to passivating variable kinds of defect states and perovskite compositions. Here, the recent progress of defect passivation toward efficient and stable PSCs was reviewed from the viewpoint of molecular structure design and device performance. To comprehensively reveal the structure‐performance correlation of passivation molecules, it was separately discussed how the functional groups, organic frameworks, and side chains affect the corresponding PV parameters of PSCs. Finally, a guideline was provided for researchers to select more suitable passivation agents, and a perspective was given on future trends in development of passivation strategies.
Here comes the sun: A comprehensive Review on the defect passivation of perovskite solar cells (PSCs) from a molecule design viewpoint is reported. First, the influence of defects on the photovoltaic parameters of PSCs is demonstrated. Then, the structure‐performance correlation of the passivation molecule is investigated. Finally, a perspective on future trends of passivation strategies is provided.
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•Zn-doped TiO2 ETL can be grown on FTO substrate below 100 °C.•Zn dopant raises the Fermi level of TiO2 by 0.1 eV.•PCE of CH3NH3PbI3 PSCs improved by 27.5% via Zn-doped ...TiO2.•Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 PSC can reach 19.04% in PCE.
The properties of the perovskite solar cells (PSCs) are highly correlated with Fermi level, trap-state density and conductivity of inorganic electron transport layer. Metal elemental doping is an effective solution to largely improve the property of oxide semiconductor thin film. In this study, zinc dopant is successfully inserted into TiO2 crystal lattice using low-temperature solution-processed route. We find that Zn-doped TiO2 films possess less trap-state density and better conductivity, compared to undoped thin films, which contributes to the promotion of short circuit current. Ultraviolet photoelectron spectroscopy displays inserting Zn2+ into TiO2 compact layer can lift up TiO2′s Fermi level, which reasonably improved the carrier dissociation and transportation. Consequently, CH3NH3PbI3 PSCs based on 4.5% Zn-doped TiO2 has obtained 17.6% power conversion efficiency (PCE), which is nearly 27.5% higher than control device (13.8%). In addition, triple-cation mixed-halide PSCs based on 4.5% Zn-doped TiO2 has obtained a PCE of 19.04%, which is almost 13.7% higher than PCE of the device with undoped sample 16.75%. These findings offer a potential low-temperature doping method in TiO2 ETL for flexible high-performance PSCs.
Objectives The goal of this study was to conduct a direct head-to-head comparison of different stem cell types in vitro for various assays of potency and in vivo for functional myocardial repair in ...the same mouse model of myocardial infarction. Background Adult stem cells of diverse origins (e.g., bone marrow, fat, heart) and antigenic identity have been studied for repair of the damaged heart, but the relative utility of the various cell types remains unclear. Methods Human cardiosphere-derived cells (CDCs), bone marrow–derived mesenchymal stem cells, adipose tissue–derived mesenchymal stem cells, and bone marrow mononuclear cells were compared. Results CDCs revealed a distinctive phenotype with uniform expression of CD105, partial expression of c-kit and CD90, and negligible expression of hematopoietic markers. In vitro, CDCs showed the greatest myogenic differentiation potency, highest angiogenic potential, and relatively high production of various angiogenic and antiapoptotic-secreted factors. In vivo, injection of CDCs into the infarcted mouse hearts resulted in superior improvement of cardiac function, the highest cell engraftment and myogenic differentiation rates, and the least-abnormal heart morphology 3 weeks after treatment. CDC-treated hearts also exhibited the lowest number of apoptotic cells. The c-kit+ subpopulation purified from CDCs produced lower levels of paracrine factors and inferior functional benefit when compared with unsorted CDCs. To validate the comparison of cells from various human donors, selected results were confirmed in cells of different types derived from individual rats. Conclusions CDCs exhibited a balanced profile of paracrine factor production and, among various comparator cell types/subpopulations, provided the greatest functional benefit in experimental myocardial infarction.
The photovoltaic performance and stability of perovskite solar cells (PSCs) are closely related to the quality of the absorption layer. Further improving the crystallinity of perovskite films is of ...great significance for the commercial application of PSCs. Here, we introduce a perovskite crystal array (PCA) with regular distribution to assist the growth of the perovskite absorption layer. The PCA provides nuclei where the crystallization can commence without overcoming the critical Gibbs free energy for nucleation and induces a controllable bottom-up crystallization process under solvent annealing. As a result, a perovskite film with high crystallinity and reduced grain boundaries was obtained. The largest grain size was over 4 μm and the average grain size was over 3 μm. PSCs based on the perovskite film with the PCA achieved power conversion efficiencies of 25.1% (certified 24.3%) and 23.1% (certified 22.3%) with aperture areas of 0.0784 cm
2
and 1.0085 cm
2
, respectively. The devices maintained 90% of their initial efficiency after operation at the maximum power point for 2000 hours under 1 sun illumination.
The PCA regularly distributing on the substrate served as templated crystals and induced a well-organized bottom-up crystallization process, which greatly improved the crystallinity of the perovskite film.
Perovskite materials with ABX
3
chemical formula have a high absorption coefficient, high mobility and low exciton binding energies, and thus are promising candidates for the next generation of ...photovoltaic devices. Doping various cations on the A site has been reported to be beneficial for improving the performance and stability of perovskite solar cells. However, the mixed cation compositions make the perovskite crystallization mechanism complicated. To better manipulate perovskite crystallization, it is essential to understand the effects of A site doping on the perovskite crystallization. Four influences of A site doping on the crystallization of perovskite films are reviewed in this paper: (1) the influences on the morphology and crystallinity of the PbI
2
layer; (2) nucleation and growth; (3) phase transition; (4) crystal orientation. At the end, we suggest that the influence of A site doping on the performance and stability of perovskite solar cells should be further studied with the help of advanced
in situ
characterization methods, theoretical computation and machine learning.
The effects of A site doping on the crystallization, including the morphology and crystallinity of the PbI
2
layer, nucleation and growth, phase transition and crystal orientation.
After decades of believing the heart loses the ability to regenerate soon after birth, numerous studies are now reporting that the adult heart may indeed be capable of regeneration, although the ...magnitude of new cardiac myocyte formation varies greatly. While this debate has energized the field of cardiac regeneration and led to a dramatic increase in our understanding of cardiac growth and repair, it has left much confusion in the field as to the prospects of regenerating the heart. Studies applying modern techniques of genetic lineage tracing and carbon-14 dating have begun to establish limits on the amount of endogenous regeneration after cardiac injury, but the underlying cellular mechanisms of this regeneration remained unclear. These same studies have also revealed an astonishing capacity for cardiac repair early in life that is largely lost with adult differentiation and maturation. Regardless, this renewed focus on cardiac regeneration as a therapeutic goal holds great promise as a novel strategy to address the leading cause of death in the developed world.
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