Currently, blade‐coated perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs), that is, greater than 20%, normally employ methylammonium lead tri‐iodide with a sub‐optimal ...bandgap. Alloyed perovskites with formamidinium (FA) cation have narrower bandgap and thus enhance device photocurrent. However, FA‐alloyed perovskites show low phase stability and high moisture sensitivity. Here, it is reported that incorporating 0.83 molar percent organic halide salts (OHs) into perovskite inks enables phase‐pure, highly crystalline FA‐alloyed perovskites with extraordinary optoelectronic properties. The OH molecules modulate the crystal growth, enhance the phase stability, passivate ionic defects at the surface and/or grain boundaries, and enhance the moisture stability of the perovskite film. A high efficiency of 22.0% under 1 sun illumination for blade‐coated PSCs is demonstrated with an open‐circuit voltage of 1.18 V, corresponding to a very small voltage deficit of 0.33 V, and significantly improved operational stability with 96% of the initial efficiency retained under one sun illumination for 500 h.
A multifunctional conjugated benzene ammonium halide is introduced to enhance phase purity, reduce trap‐state density, and suppress nonradiative charge recombination. Blade‐coated solar cells based on stabilized formamidinium‐dominant perovskite compositions deliver an impressive efficiency of 22.0% and an improved operational stability.
The efficiencies of perovskite solar cells (PSCs) are now reaching such consistently high levels that scalable manufacturing at low cost is becoming critical. However, this remains challenging due to ...the expensive hole-transporting materials usually employed, and difficulties associated with the scalable deposition of other functional layers. By simplifying the device architecture, hole-transport-layer-free PSCs with improved photovoltaic performance are fabricated via a scalable doctor-blading process. Molecular doping of halide perovskite films improved the conductivity of the films and their electronic contact with the conductive substrate, resulting in a reduced series resistance. It facilitates the extraction of photoexcited holes from perovskite directly to the conductive substrate. The bladed hole-transport-layer-free PSCs showed a stabilized power conversion efficiency above 20.0%. This work represents a significant step towards the scalable, cost-effective manufacturing of PSCs with both high performance and simple fabrication processes.
Multiple‐cation lead mixed‐halide perovskites (MLMPs) have been recognized as ideal candidates in perovskite solar cells in terms of high efficiency and stability due to decreased open‐circuit ...voltage loss and suppressed yellow phase formation. However, they still suffer from an unsatisfactory long‐term moisture stability. In this study, phosphorus‐containing Lewis acid and base molecules are employed to improve device efficiency and stability based on their multifunction including recombination reduction, phase segregation suppression, and moisture resistance. The strong fluorine‐containing Lewis acid treatment can achieve a champion PCE of 22.02%. Unencapsulated and encapsulated devices retain 63% and 80% of the initial efficiency after 14 days of aging under 75% and 85% relative humidity, respectively. The better passivation of Lewis acid implies more halide defects than Pb defects at the MLMP surface. This unbalanced defect type results from phase segregation that is the synergistic effect of Cs and halide ion migrations. Identifying defect type based on different passivation effects is beneficial to not only choose suitable passivators to boost the efficiency and slow down the moisture degradation of MLMP solar cells, but also to understand the mechanism of defect‐assisted moisture degradation.
A strong fluorine‐containing Lewis acid tris(pentafluorophenyl) phosphine (TPFP) is developed to passivate mixed perovskite solar cells, achieving a champion efficiency of 22.02% and a high stability under 85% relative humidity. The moisture degradation mechanism is phase segregation of I‐rich black phase and Cs/Br‐rich yellow phase resulting from water‐assisted synergistic Cs and halide ion migrations.
Covariant phase space with boundaries Harlow, Daniel; Wu, Jie-qiang
The journal of high energy physics,
10/2020, Letnik:
2020, Številka:
10
Journal Article
Recenzirano
Odprti dostop
A
bstract
The covariant phase space method of Iyer, Lee, Wald, and Zoupas gives an elegant way to understand the Hamiltonian dynamics of Lagrangian field theories without breaking covariance. The ...original literature however does not systematically treat total derivatives and boundary terms, which has led to some confusion about how exactly to apply the formalism in the presence of boundaries. In particular the original construction of the canonical Hamiltonian relies on the assumed existence of a certain boundary quantity “
B
”, whose physical interpretation has not been clear. We here give an algorithmic procedure for applying the covariant phase space formalism to field theories with spatial boundaries, from which the term in the Hamiltonian involving
B
emerges naturally. Our procedure also produces an additional boundary term, which was not present in the original literature and which so far has only appeared implicitly in specific examples, and which is already nonvanishing even in general relativity with sufficiently permissive boundary conditions. The only requirement we impose is that at solutions of the equations of motion the action is stationary modulo future/past boundary terms under arbitrary variations obeying the spatial boundary conditions; from this the symplectic structure and the Hamiltonian for any diffeomorphism that preserves the theory are unambiguously constructed. We show in examples that the Hamiltonian so constructed agrees with previous results. We also show that the Poisson bracket on covariant phase space directly coincides with the Peierls bracket, without any need for non-covariant intermediate steps, and we discuss possible implications for the entropy of dynamical black hole horizons.
High‐efficiency perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising alternatives for silicon‐based solar cells. At present, the key point for commercialization of PSCs and OSCs ...is realizing large‐scale production while maintaining the same high efficiency as small‐area ones. In this review, the blade‐coating method for preparing large‐area films is introduced first and the recent advances of blade‐coated OSCs and PSCs are summarized. Then, the effects of blading parameters on the crystal growth and film formation of the light‐harvesting materials are discussed. Moreover, the limitations and advantages of making high‐quality films via blade‐coating are discussed. Finally, some strategies for the up‐scaling of solar cells via blade‐coating are proposed.
In this review, the recent advances in blade‐coated perovskite solar cells and organic solar cells are summarized. The technological details and issues are discussed with an outlook.
Sn perovskite solar cells have been regarded as one of the most promising alternatives to the Pb‐based counterparts due to their low toxicity and excellent optoelectronic properties. However, the Sn ...perovskites are notorious to feature heavy p‐doping characteristics and possess abundant vacancy defects, which result in under‐optimized interfacial energy level alignment and severe nonradiative recombination. Here, we reported a synergic “electron and defect compensation” strategy to simultaneously modulate the electronic structures and defect profiles of Sn perovskites via incorporating a traced amount (0.1 mol %) of heterovalent metal halide salts. Consequently, the doping level of modified Sn perovskites was altered from heavy p‐type to weak p‐type (i.e. up‐shifting the Fermi level by ∼0.12 eV) that determinately reducing the barrier of interfacial charge extraction and effectively suppressing the charge recombination loss throughout the bulk perovskite film and at relevant interfaces. Pioneeringly, the resultant device modified with electron and defect compensation realized a champion efficiency of 14.02 %, which is ∼46 % higher than that of control device (9.56 %). Notably, a record‐high photovoltage of 1.013 V was attained, corresponding to the lowest voltage deficit of 0.38 eV reported to date, and narrowing the gap with Pb‐based analogues (∼0.30 V).
Synergic electron and defect compensation on Sn perovskites has been realized via alloying heterovalent metal halide salts. This concurrently optimized the interfacial carrier dynamics, compensated the prevailing vacancy defects and minimized the nonradiative recombination loss throughout the devices, thus affording best efficiency up to 14.02 % characterized by a record high photovoltage of 1.013 V and the lowest voltage deficit of 0.38 V.
The performances of electron‐transport‐layer (ETL)‐free perovskite solar cells (PSCs) are still inferior to ETL‐containing devices. This is mainly due to severe interfacial charge recombination ...occurring at the transparent conducting oxide (TCO)/perovskite interface, where the photo‐injected electrons in the TCO can travel back to recombine with holes in the perovskite layer. Herein, we demonstrate for the first time that a non‐annealed, insulating, amorphous metal oxyhydroxide, atomic‐scale thin interlayer (ca. 3 nm) between the TCO and perovskite facilitates electron tunneling and suppresses the interfacial charge recombination. This largely reduced the interfacial charge recombination loss and achieved a record efficiency of 21.1 % for n‐i‐p structured ETL‐free PSCs, outperforming their ETL‐containing metal oxide counterparts (18.7 %), as well as narrowing the efficiency gap with high‐efficiency PSCs employing highly crystalline TiO2 ETLs.
A non‐annealed, ultrathin, amorphous metal oxyhydroxide was introduced to suppress interfacial charge recombination and reduce energy loss in electron‐transport‐layer (ETL)‐free perovskite solar cells. The cells achieve a record efficiency of 21.1 %, outperforming their ETL‐containing metal oxide counterparts (18.7 %).
Microscopic design and morphological engineering of the semiconducting metal oxide as electron‐transporting layers (ETLs) is of vital importance for optical enhancement, photonic structuring, and ...charge collection optimization within optoelectronic devices. Herein, nanowire‐coated, branched macroporous titania (BMT) thin films are reported as a new type of ETL prepared by using silica spheres as a sacrificial template, followed by a sol–gel and subsequent alkaline‐assisted etching process. The BMT films feature 3D hierarchical structures and interconnected networks with tunable pore sizes, branch densities, and film thicknesses. The titania films are employed as ETLs in perovskite solar cells (PSCs), resulting in remarkable power conversion efficiencies (PCEs) of 20.1%; a noticeable 16% increase compared with titania nanowire (TNW) ETL‐based counterparts (PCE = 17.3%). The superior device performance of the BMT‐based PSCs can be attributed to the maximized light harvesting and charge collection capabilities. These beneficial properties are derived from the effective infiltration of the perovskite precursor into the titania macropores, efficient light confinement within the macropore structure, and the textured perovskite capping layer, as well as enhanced charge transport and reduced charge recombination through the BMT architecture. This work demonstrates a simple and effective approach for constructing branched macroporous metal‐oxide photoelectrodes toward high‐performance photovoltaic devices.
A template‐assisted solution‐processed technique is developed to fabricate 3D nanowire‐coated macroporous titania thin films with outstanding optical and electrical properties. Perovskite solar cells based on newly prepared TiO2 electron‐transporting layer deliver an impressive power conversion efficiency of up to 20.1% owing to enhanced light harvesting and facilitated charge collection.
Simplified perovskite solar cells (PSCs) were fabricated with the perovskite layer sandwiched and encapsulated between carbon‐based electron transport layer (ETL) and counter electrode (CE) by a ...fully blade‐coated process. A self‐assembled monolayer of amphiphilic silane (AS) molecules on transparent conducting oxide (TCO) substrate appeals to the fullerene ETL deposition and preserves its integrity against the solvent damage. The AS serves as a “molecular glue” to strengthen the adhesion toughness at the TCO/ETL interface via robust chemical interaction and bonding, facilitating the interfacial charge extraction, increasing PCEs by 77 % and reducing hysteresis. A PCE of 18.64 % was achieved for the fully printed devices, one of the highest reported for carbon‐based PSCs. AS‐assisted interfacial linkage and carbon‐material‐assisted self‐encapsulation enhance the stability of the PSCs, which did not experience performance degradation when stored at ambient conditions for over 3000 h.
A simple amphiphilic silane interfacial linkage strategy was employed to realize fully‐printed all carbon‐based perovskite photovoltaics, achieving a high efficiency of 18.64 %, accompanied by excellent device stability over 3000 hours.
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