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All-perovskite tandem solar cells have shown great promise in breaking the Shockley–Queisser limit of single-junction solar cells. However, the efficiency improvement of all-perovskite tandem solar cells is largely hindered by the surface defects induced non-radiative recombination loss in Sn–Pb mixed narrow bandgap perovskite films. Here, we report a surface reconstruction strategy utilizing a surface polishing agent, 1,4-butanediamine, together with a surface passivator, ethylenediammonium diiodide, to eliminate Sn-related defects and passivate organic cation and halide vacancy defects on the surface of Sn–Pb mixed perovskite films. Our strategy not only delivers high-quality Sn–Pb mixed perovskite films with a close-to-ideal stoichiometric ratio surface but also minimizes the non-radiative energy loss at the perovskite/electron transport layer interface. As a result, our Sn–Pb mixed perovskite solar cells with bandgaps of 1.32 and 1.25 eV realize power conversion efficiencies of 22.65% and 23.32%, respectively. Additionally, we further obtain a certified power conversion efficiency of 28.49% of two-junction all-perovskite tandem solar cells. The efficiency of all-perovskite tandem solar cells is impacted by the nonradiative recombination loss in Sn–Pb mixed narrow bandgap perovskite films. Here, the authors utilize a surface polishing agent with surface passivator to deliver films with a close-to-ideal stoichiometric ratio surface. [ABSTRACT FROM AUTHOR]

All‐perovskite tandem solar cells (ATSCs) present a remarkable opportunity to overcome the Shockley–Queisser efficiency limit of single‐junction solar cells. However, the stability of ATSCs significantly lags that of their pure Pb‐based single‐junction counterparts. Recent studies have identified that the widely used poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) hole transport layer in narrow‐bandgap (NBG) tin–lead (Sn–Pb) perovskite solar cells (PSCs) hinders the efficiency and stability. Herein, a patching strategy to optimize the interface between perovskite and PEDOT:PSS is proposed. Both theoretical and experimental studies reveal that PenA+ and Ac− can decrease defect states at the interface and strengthen the binding between PEDOT:PSS and Sn–Pb perovskite. Furthermore, the pentylammonium acetate (PenAAc) interlayer improves carrier extraction and suppresses the oxidation of Sn2+ to Sn4+. With the PenAAc buried layer, the fabricated NBG PSCs obtain an impressive power conversion efficiency (PCE) of 21.86%, along with significantly enhanced device stability. By integrating the buried passivated NBG Sn–Pb perovskite with a 1.75 eV wide‐bandgap PSC, the two‐terminal ATSC achieves a PCE of 26.54%. This work provides a valuable approach to fabricate efficient and stable NBG PSCs. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiOX) is a desirable hole‐transporting material for perovskite solar cells owing to their merits of low‐cost, stable, and readily scalable. However, the NiOX|perovskite interface suffers from serious recombination and poor photostability because of the interfacial redox reactions. Herein, NiOX nanoparticles with tunable size have been synthesized at low temperatures by controlling the reactivity of the hydrolysis reaction. A self‐assembled monolayer composed of a ruthenium complex, i.e., C106, is then introduced to optimize the interfacial properties. The C106 molecule chemically bonds to NiOX via carboxyl acid group, which passivates the surface defects of NiOX and suppresses the negative redox reaction at the interface. The modification leads to an improvement in perovskite film morphology, crystallization, and band alignment. As a result, the efficiency of solar cells has been improved from 18.1% to 20.5%. More importantly, the modified solar cells retain >80% of their initial performance after continuous operation under 100 mW cm−2 irradiation for 800 h, which is much enhanced than the unmodified devices. [ABSTRACT FROM AUTHOR]

Rapid processing technologies of perovskite solar cells (PSCs) offer an exciting approach to raise the rate of production. Herein, a rapid microwave‐annealing process (MAP) is reported to replace the traditional hotplate annealing process (HAP) and the processing period of perovskite is reduced to less than 1 min. Benefiting from the penetrability and simultaneity of microwave irradiation, the MAP method can effectively eliminate miscellaneous phases and thus achieve >1 µm large‐size crystal grains in perovskite films. These MAP treated perovskite films exhibit pure crystalline phase, long charge‐carrier lifetime, and low defect density, which can substantially improve the PSC efficiency without requiring an additional enhancer/passivation layer. The inverted planar PSCs present enhanced power conversion efficiency from 18.33% (HAP) to 21.59% (MAP) and good stability of >1000 h lifetime without encapsulation under ambient conditions. In addition, MAP can be applied to a large‐size (10 cm × 10 cm) perovskite film fabrication as well as a broader tolerance in environmental temperature and precursor concentration, making it a reliable method for repeatably practical fabrication of perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Perovskite solar cells can be produced by a solution process and have achieved power conversion efficiency over 20% as well as improving long-term stability, offering great potential for a low cost, high efficiency photovoltaic technology. An increasing effort has been shifted to Lab-to-Fab translation, where device manufacture is accomplished by using a fully scalable printing process. One remarkable bottleneck for upscaling the device is, however, the lack of scalable hole-transport materials (HTMs) that can form the desired morphology during the printing fabrication. In this manuscript, we apply a twisted but fully π-conjugated 2,2′,7,7′-tetrakis(N,N-di- p -methoxyphenyl)amine-9,9′-bifluorenylidene (Bifluo-OMeTAD) into slot-die coated devices, which exhibits excellent film forming properties and outperforms the well-known Spiro-OMeTAD HTM. The improved film forming properties of Bifluo-OMeTAD are achieved via molecular design, with the chemical structure of Bifluo-OMeTAD effectively suppressing crystallization during printing. A power conversion efficiency of 14.7% is achieved in the fully slot-die coated devices based on Bifluo-OMeTAD, outperforming previous reported values for all-printed perovskite solar cells. Therefore, Bifluo-OMeTAD has attractive potential to replace Spiro-OMeTAD for the large scale roll-to-roll production of fully slot-die coated perovskite solar cells. [ABSTRACT FROM AUTHOR]

Perovskite-based solar cells are generally assembled as planar structures comprising a flat organoammonium metal halide perovskite layer, or mesoscopic structures employing a mesoporous metal-oxide scaffold into which the perovskite material is infiltrated. To present, little attention has been directed toward the texturing of the perovskite material itself. Herein, a textured CH3NH3PbI3 morphology formed through a thin mesoporous TiO2 seeding layer and a gas-assisted crystallization method is reported. The textured morphology comprises a multitiered nanostructure, which allows for significant improvements in the light harvesting and charge extraction performance of the solar cells. Due to these improvements, average short-circuit current densities for a batch of 28 devices are in excess of 22 mA cm−2, and the maximum recorded power conversion efficiency is 16.3%. The performance gains concomitant with this textured CH3NH3PbI3 morphology provide further insights into how control of the perovskite microstructure can be used to enhance the cell performance. [ABSTRACT FROM AUTHOR]

The microstructure of solution-processed organometallic lead halide perovskite thin films prepared by the 'gas-assisted' method is investigated with synchrotron-based techniques. Using a combination of GIWAXS and NEXAFS spectroscopy the orientational alignment of CH3NH3PbI3 crystallites and CH3NH3+ cations are separately probed. The GIWAXS results reveal a lack of preferential orientation of CH3NH3PbI3 crystallites in 200-250 nm thick films prepared on both planar TiO2 and mesoporous TiO2. Relatively high efficiencies are observed for device based on such films, with 14.3% achieved for planar devices and 12% for mesoporous devices suggesting that highly oriented crystallites are not crucial for good cell performance. Oriented crystallites however are observed in thinner films (≈60 nm) deposited on planar TiO2 (but not on mesoporous TiO2) indicating that the formation of oriented crystallites is sensitive to the kinetics of solvent evaporation and the underlying TiO2 morphology. NEXAFS measurements on all samples found that CH3NH3+ cations exhibit a random molecular orientation with respect to the substrate. The lack of any NEXAFS dichroism for the thin CH3NH3PbI3 layer deposited on planar TiO2 in particular indicates the absence of any preferential orientation of CH3NH3+ cations within the CH3NH3PbI3 unit cell for as-prepared layers, that is, without any electrical poling. [ABSTRACT FROM AUTHOR]

Thin-film photovoltaics based on alkylammonium lead iodide perovskite light absorbers have recently emerged as a promising low-cost solar energy harvesting technology. To date, the perovskite layer in these efficient solar cells has generally been fabricated by either vapor deposition or a two-step sequential deposition process. We report that flat, uniform thin films of this material can be deposited by a one-step, solvent-induced, fast crystallization method involving spin-coating of a DMF solution of CH3NH3PbI3 followed immediately by exposure to chlorobenzene to induce crystallization. Analysis of the devices and films revealed that the perovskite films consist of large crystalline grains with sizes up to microns. Planar heterojunction solar cells constructed with these solution-processed thin films yielded an average power conversion efficiency of 13.9±0.7 % and a steady state efficiency of 13 % under standard AM 1.5 conditions. [ABSTRACT FROM AUTHOR]

Upscaling the perovskite solar cell (PSC) while avoiding losses in the power conversion efficiency presents a substantial challenge, especially when transitioning from ≤1 cm2 cells to ≥10 cm2 modules. In addition to the fabrication of key functional layers, scalable technologies for surface passivation, considered indispensable for achieving high‐performance PSCs, are urgently required. However, studies on this topic remain limited. In this study, an industry‐ready slot‐die coating method for the effective passivation of perovskite films as a practical alternative is developed to the spin‐coating procedures commonly used in research. The coating conditions and molecular structure of the passivation agent are systematically optimized to achieve high‐quality film morphology and substantially suppress interface recombination. 2‐chloro‐5‐(trifluoromethyl)‐phenylammonium bromide exhibited the best results, improving the open‐circuit voltage of cells and subcells in a module by 80 ± 4 and 72 ± 10 mV, respectively. Correspondingly, the larger‐area (active area: 10 cm2) modules sustained the highest efficiency of 21.9% under simulated 1‐sun irradiation. The encapsulated devices retained 94% of their initial performances after 750 h of continuous operation. The proposed surface‐passivation slot‐die technology is compatible with high‐throughput processes and is employable for large‐scale PSC fabrication. [ABSTRACT FROM AUTHOR]

Perovskite solar cells represent a promising photovoltaic technology, which achieves record power conversion efficiencies over 24%. However, a problem on the commercial processing is the unavoidable efficiency loss during the scalable fabrication of perovskite solar module. The efficient and reliable fabrications of high‐quality large‐area perovskite films guarantee commercialized up‐scaling of perovskite solar cells with high efficiency. Herein, a simple dynamic antisolvent quenching (DAS) process is presented to understand large‐area uniform perovskite films to obtain an efficient perovskite solar module. This method provides a facile and universal approach to fabricate cracks‐free and uniform large‐area mixed‐cation perovskite films. A champion module device (10 × 10 cm2) with efficiency of 17.82% (another module with certified efficiency of 17.4%) is obtained using DAS process. [ABSTRACT FROM AUTHOR]

Upscaling efficient and stable perovskite layers is one of the most challenging issues in the commercialization of perovskite solar cells. Here, a lead halide–templated crystallization strategy is developed for printing formamidinium (FA)–cesium (Cs) lead triiodide perovskite films. High-quality large-area films are achieved through controlled nucleation and growth of a lead halide•N-methyl-2-pyrrolidone adduct that can react in situ with embedded FAI/CsI to directly form a-phase perovskite, sidestepping the phase transformation from d-phase. A nonencapsulated device with 23% efficiency and excellent long-term thermal stability (at 85°C) in ambient air (~80% efficiency retention after 500 hours) is achieved with further addition of potassium hexafluorophosphate. The slot die–printed minimodules achieve champion efficiencies of 20.42% (certified efficiency 19.3%) and 19.54% with an active area of 17.1 and 65.0 square centimeters, respectively. [ABSTRACT FROM AUTHOR]

The band edges of metal-halide perovskites with a general chemical structure of ABX3 (A, usually a monovalent organic cation; B, a divalent cation; and X, a halide anion) are constructed mainly of the orbitals from B and X sites. Hence, the structural and compositional varieties of the inorganic B–X framework are primarily responsible for regulating their electronic properties, whereas A-site cations are thought to only help stabilize the lattice and not to directly contribute to near-edge states. We report a p-conjugation–induced extension of electronic states of A-site cations that affects perovskite frontier orbitals. The p-conjugated pyrene-containing A-site cations electronically contribute to the surface band edges and influence the carrier dynamics, with a properly tailored intercalation distance between layers of the inorganic framework. The ethylammonium pyrene increased hole mobilities, improved power conversion efficiencies relative to that of a reference perovskite, and enhanced device stability. [ABSTRACT FROM AUTHOR]

Review: 133 refs. [ABSTRACT FROM AUTHOR]