Small-molecule hole transporting materials based on methoxydiphenylamine-substituted fluorene fragments were synthesized and incorporated into a perovskite solar cell, which displayed a power ...conversion efficiency of up to 19.96%, one of the highest conversion efficiencies reported. The investigated hole transporting materials were synthesized in two steps from commercially available and relatively inexpensive starting reagents, resulting in up to fivefold cost reduction of the final product compared with spiro-OMeTAD. Electro-optical and thermoanalytical measurements such as UV/Vis, thin-film conductivity, hole mobility, DSC, TGA, ionization potential and current voltage scans of the full perovskite solar cells have been carried out to characterize the new materials.
Metal halide perovskite solar cells (PSCs) have emerged as an important direction for photovoltaic research. Although the power conversion efficiency (PCE) of lead‐based PSCs has reached 25.7%, still ...the toxicity of Pb remains one main obstacle for commercial adoption. Thus, to address this issue, Pb‐free perovskites have been proposed. Among them, tin‐based perovskites have emerged as promising candidates. Unfortunately, the fast oxidation of Sn2+ to Sn4+ leads to low stability and efficiency. Many strategies have been implemented to address these challenges in Sn‐based PSCs. This work introduces stability and efficiency improvement strategies for pure Sn‐based PSCs by optimization of the crystal structure, processing and interfaces as well as, implementation of low‐dimension structures. Finally, new perspectives for further developing Sn‐based PSCs are provided.
The review discusses the stability of crystal structure, summarizes the factors affecting crystal stability, and analyzes the physical properties of crystals. Then, the preparation of tin‐based perovskite devices is summarized and discussed in detail with respect to four aspects: thin film manufacturing processes, additive selection, preparation of low‐dimensional structures and selection of interface layers.
Negative capacitance in the low-frequency domain and inverted hysteresis are familiar features in perovskite solar cells, which origin is still under discussion. Here we use impedance spectroscopy to ...analyze these responses in methylammonium lead bromide cells treated with lithium cations at the electron-selective layer/perovskite interface and in iodide devices exposed to different relative humidity conditions. Employing the surface polarization model, we obtain a time constant associated with the kinetics of the interaction of ions/vacancies with the surface, τkin, in the range of 100–102 s for all the cases exhibiting both features. These interactions lead to a decrease in the overall recombination resistance, modifying the low-frequency perovskite response and yielding a flattening of the cyclic voltammetry. As a consequence of these results we find that negative capacitance and inverted hysteresis lead to a decrease in the fill factor and photovoltage values.
A general strategy for the in‐plane structuring of organic–inorganic perovskite films is presented. The method is used to fabricate an industrially relevant distributed feedback (DFB) cavity, which ...is a critical step toward all‐electrially pumped injection laser diodes. This approach opens the prospects of perovskite materials for much improved optical control in LEDs, solar cells, and also toward applications as optical devices.
Organo-lead halide perovskites have emerged as promising light harvesting materials for solar cells. The ability to prepare high quality films with a low concentration of defects is essential for ...obtaining high device performance. Here, we advance the procedure for the fabrication of efficient perovskite solar cells (PSCs) based on mechanochemically synthesized MAPbI3. The use of mechano-perovskite for the thin film formation provides a high degree of control of the stoichiometry and allows for the growth of relatively large crystalline grains. The best device achieved a maximum PCE of 17.5% from a current–voltage scan (J–V), which stabilized at 16.8% after 60 s of maximum power point tracking. Strikingly, PSCs based on MAPbI3 mechanoperovskite exhibit lower “hysteretic” behavior in comparison to that comprising MAPbI3 obtained from the conventional solvothermal reaction between PbI2 and MAI. To gain a better understanding of the difference in J–V hysteresis, we analyze the charge/ion accumulation mechanism and identify the defect energy distribution in the resulting MAPbI3 based devices. These results indicate that the use of mechanochemically synthesized perovskites provides a promising strategy for the formation of crystalline films demonstrating slow charge recombination and low trap density.
Metal halide perovskites have emerged as exceptional semiconductors for optoelectronic applications. Substitution of the monovalent cations has advanced luminescence yields and device efficiencies. ...Here, we control the cation alloying to enhance optoelectronic performance through alteration of the charge carrier dynamics in mixed-halide perovskites. In contrast to single-halide perovskites, we find high luminescence yields for photoexcited carrier densities far below solar illumination conditions. Using time-resolved spectroscopy we show that the charge carrier recombination regime changes from second to first order within the first tens of nanoseconds after excitation. Supported by microscale mapping of the optical bandgap, electrically gated transport measurements and first-principles calculations, we demonstrate that spatially varying energetic disorder in the electronic states causes local charge accumulation, creating p- and n-type photodoped regions, which unearths a strategy for efficient light emission at low charge-injection in solar cells and light-emitting diodes.Localized photodoping in mixed-cation perovskites is shown to modify charge-carrier recombination and thus offer a route for more efficient light emission.
Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of ...device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5‐aminovaleric acid is reported. A trade‐off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single‐crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO2/ZrO2/C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability.
As reflected in the fragility of state‐of‐the‐art perovskite solar cells, mechanical reliability has too long been an afterthought in their development. The aim of this work is to understand the effects of cation composition (combinations of methylammonium, formamidinium, cesium, butylammonium, and 5‐aminovaleric acid) on perovskite mechanical integrity and determine design criteria to increase reliability toward the development of module‐scale devices.
State-of-the-art cesium-containing multiple-cation perovskites are generally synthesized from stock solutions of perovskite precursors and CsI in DMSO and DMF. However, compositional diversity of ...multi-component perovskites is significantly hampered due to the poor solubility of other cesium halides in these solvents. Here, we show how insoluble CsCl, as a new source of cesium cation, can be integrated into a multiple-cation perovskite material by a one-step method involving grinding of the precursors. The resulting polycrystalline powder is fully soluble in a DMSO/DMF mixture and allows formation of perovskite thin films. 133Cs solid-state MAS NMR data indicate that the cesium cation is almost fully (90%) incorporated into the 3D perovskite lattice, while the remaining 10% forms a cesium-rich mixed-halide secondary phase. The planar heterojunction device fabricated using this original mechanoperovskite yielded a power conversion efficiency of 19.12% and an open circuit voltage of 1.16 V. Moreover, we show that the introduction of CsCl improves both interfacial and bulk photovoltaic metrics. Our one-step approach provides an efficient general method for incorporating poorly soluble salts into multi-component perovskite crystal lattices.
The insoluble CsCl, as a new source of cesium cation, is shown to integrate into a multiple-cation perovskite material by a one-step method involving grinding of the precursors. The resulting polycrystalline powder is fully soluble in a DMSO/DMF mixture and allows formation of perovskite thin films and consequently planar based solar cells. Display omitted
•Mechanochemistry was employed to integrate poorly soluble alkali metal salt into multiple-cation perovskite lattice.•133Cs solid-state MAS NMR was used to probe microscopic composition of Cs-containing lead halide perovskites.•The planar heterojunction device yielded a power conversion efficiency of 19.12% and an open circuit voltage of 1.16 V.
While it is well recognized in the literature that modularity is a very important enabler for reconfigurability in manufacturing systems, there is very limited practical guidance on how the various ...required functions of a production system should be grouped into modules. In this work, a new heuristic approach is developed and presented, to aid the system developer in the identification and synthesis of potential modules during the early design stage of a reconfigurable manufacturing system. The work involves the identification of key module drivers for such systems, and of key criteria that can be used to facilitate the optimization of the granularity and effectiveness of the system. The results are presented in the form of a semi-algorithmic design tool that can be easily understood and used by the developer. The tool is applied to three very different industrial case studies, and is shown to be applicable to various manufacturing scenarios and sub-sectors. The use of the new tool is compared to the use of a design structure matrix approach to function clustering for module synthesis, and is shown to be easier and more objective in its application.
The rapid development of Internet of Things mobile terminals has accelerated the market's demand for portable mobile power supplies and flexible wearable devices. Here, an embedded metal‐mesh ...transparent conductive electrode (TCE) is prepared on poly(ethylene terephthalate) (PET) using a novel selective electrodeposition process combined with inverted film‐processing methods. This embedded nickel (Ni)‐mesh flexible TCE shows excellent photoelectric performance (sheet resistance of ≈0.2–0.5 Ω sq−1 at high transmittance of ≈85–87%) and mechanical durability. The PET/Ni‐mesh/polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS PH1000) hybrid electrode is used as a transparent electrode for perovskite solar cells (PSCs), which exhibit excellent electric properties and remarkable environmental and mechanical stability. A power conversion efficiency of 17.3% is obtained, which is the highest efficiency for a PSC based on flexible transparent metal electrodes to date. For perovskite crystals that require harsh growth conditions, their mechanical stability and environmental stability on flexible transparent embedded metal substrates are studied and improved. The resulting flexible device retains 76% of the original efficiency after 2000 bending cycles. The results of this work provide a step improvement in flexible PSCs.
Research on flexible mobile energy‐supply devices will promote the development of the Internet of Things. An embedded metal nickel (Ni)‐mesh transparent conductive electrode is used as a flexible substrate for perovskite solar cells (PSCs). These Ni‐mesh‐based PSCs exhibit excellent electric properties and remarkable environmental and mechanical stability.
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