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We reported a surface ligand manipulation strategy for hybrid MAPbI3 perovskite quantum dots (PeQDs) using methylamine iodide (MAI), methylamine thiocyanate (MASCN) and methylamine acetate (MAAc) salts. After MAI salt post-treatment, a record high efficiency of 14.98% was obtained for MAPbI3 PeQD solar cells together with enhanced ambient stability. [ABSTRACT FROM AUTHOR]

The mixed cation colloidal Cs1−XFAXPbI3 perovskite quantum dots (PQDs) obtained by cation exchange between CsPbI3 and FAPbI3 PQDs have been reported to exhibit enhanced photovoltaic performance. However, the cation exchange mechanism requires further in-depth investigation in terms of both material properties and device application. In this work, the impact of PQD weight ratio, PQD concentration, and host solvent polarity during cation exchange is comprehensively investigated for the first time. In addition, the whole exchange process under varying conditions is monitored by photoluminescence spectroscopy. As a result, we observe extremely fast cation exchange (∼20 min) under a condition at a CsPbI3/FAPbI3 PQD weight ratio of 1:1, a concentration of 70 mg/ml, and a host solvent using toluene. Moreover, we directly fabricate a PQD solar cell device using these obtained mixed cation Cs0.5FA0.5PbI3 PQDs and achieved an enhanced power conversion efficiency of 14.58%. We believe that these results would provide more insights into the cation exchange in emerging PQDs toward efficient photovoltaic fabrication and application. [ABSTRACT FROM AUTHOR]

Lead halide perovskite quantum dots (PQDs) exhibit properties tunability and solution processability, rending them highly promising for optoelectronic applications. To overcome the compositional limits of thin‐film perovskite and achieve mixed A‐site PQDs, a post‐synthetic cation‐exchange process, driven by the intrinsic ionic character as well as the dynamic surface structure within the PQDs, emerges as a highly efficient approach. The cation‐exchange process can be precisely regulated by manipulating PQD‐situated environment, such as the cation species, stoichiometric ratios, and surface ligand conditions, leading to tunable optical bandgap, improved stability, and enhanced carrier lifetime over the single A‐site PQDs. These advancements hold immense potential for elevating the performance of PQD‐based optoelectronic devices. In this perspective, a timely summary and outlook on the emergence and developments of cation exchange in functional PQDs is presented, as well as the intrinsic cation‐exchange mechanism and properties of these resultant‐mixed‐cation PQDs. It is believed that these detailed discussions are beneficial for advancing further development of cation exchange and utilization of mixed‐cation PQDs toward functional optoelectronic applications. [ABSTRACT FROM AUTHOR]

Phase transition dynamics are an important concern in the wide applications of metal halide perovskites, which fundamentally determine the optoelectronic properties and stabilities of perovskite materials and devices. However, a more in-depth understanding of such a phase transition process with real atomic resolution is still limited by the immature low-dose electron microscopy and in situ imaging studies to date. Here, we apply an emergent low-dose imaging technique to identify different phase structures (α, β and γ) in CsPbI3 nanocrystals during an in-situ heating process. The rotation angles of PbI6 octahedrons can be measured in these images to quantitatively describe the thermal-induced phase distribution and phase transition. Then, the dynamics of such a phase transition are studied at a macro time scale by continuously imaging the phase distribution in a single nanocrystal. The structural evolution process of CsPbI3 nanocrystals at the particle level, including the changes in morphology and composition, is also visualized with increasing temperature. These results provide atomic insights into the transition dynamics of perovskite phases, indicating a long-time transition process with obvious intermediate states and spatial distribution that should be generally considered in the further study of structure-property relations and device performance. Phase transition dynamics are an important concern in the wide applications of metal halide perovskites. Here authors apply low-dose imaging technique to reveal the phase transition dynamics of CsPbI3 during in-situ heating process with atomic resolution. [ABSTRACT FROM AUTHOR]

Dimensionality engineering involving the low‐dimensional and 3D perovskites has been demonstrated as an efficient promising strategy to modulate interfacial energy loss as well as instability in perovskite solar cells (PSCs). Herein, the use of fluorinated Cesium Lead Iodide (CsPbI3) perovskite quantum dot (PQD) is first reported as interface modification layer for PSCs. The binding between the CsPbI3 PQD surface and native oleic acid (OLA)/oleylamine (OAm) ligands is governed by a dynamic adsorption–desorption equilibrium. Perfluorooctanoic acid (PFA) with stronger binding affinity and more hydrophobic nature is explored to partially replace OLA to prepare the fluorinated ligand capped CsPbI3 PQDs (F‐CsPbI3). Through optimization of the addition of PFA during hot‐injection synthesis, the in situ treated F‐CsPbI3 PQDs display reduced surface defect states, higher photoluminescence quantum yields together with improved stability. Subsequently, both CsPbI3 and F‐CsPbI3 PQDs are utilized as interface engineering layer in PSCs, delivering the best efficiency values of 21.99% and 23.42%, respectively, which is significantly enhanced compared to the control device (20.37%). More importantly, benefiting from its more hydrophobic properties, the F‐CsPbI3 PQD treated device exhibits excellent ambient storage stability (25 °C, relative humidity: 35–45%), retaining over 80% of its initial efficiency after 1500 h aging. [ABSTRACT FROM AUTHOR]

Organic–inorganic formamidinium lead triiodide (FAPbI3) hybrid perovskite quantum dot (QD) is of great interest to photovoltaic (PV) community due to its narrow band gap, higher ambient stability, and long carrier lifetime. However, the surface ligand management of FAPbI3 QD is still a key hurdle that impedes the design of high‐efficiency solar cells. Herein, this study first develops a solution‐mediated ligand exchange (SMLE) for preparing FAPbI3 QD film with enhanced electronic coupling. By dissolving optimal methylammonium iodide (MAI) into antisolvent to treat the FAPbI3 QD solution, the SMLE can not only effectively replace the long‐chain ligands, but also passivate the A‐ and X‐site vacancies. By combining experimental and theoretical results, this study demonstrates that the SMLE engineered FAPbI3 QD exhibits lower defect density, which is beneficial for fabricating high‐quality QD arrays with desired morphology and carrier transport. Consequently, the SMLE FAPbI3 QD based solar cell outputs a champion efficiency of 15.10% together with improved long‐term ambient storage stability, which is currently the highest reported value for hybrid perovskite QD solar cells. These results would provide new design principle of hybrid perovskite QDs toward high‐performance optoelectronic application. [ABSTRACT FROM AUTHOR]

Highlights: The introduction of hydroiodic acid (HI) manipulates the dynamic conversion of PbI2 into highly coordinated species to optimize the nucleation and growth kinetics. The addition of HI enables the fabrication of CsPbI3 perovskite quantum dots with reduced defect density, enhanced crystallinity, higher phase purity, and near-unity photoluminescence quantum yield. The efficiency of CsPbI3 perovskite quantum dot solar cells was enhanced from 14.07% to 15.72% together with enhanced storage stability. All-inorganic CsPbI3 quantum dots (QDs) have demonstrated promising potential in photovoltaic (PV) applications. However, these colloidal perovskites are vulnerable to the deterioration of surface trap states, leading to a degradation in efficiency and stability. To address these issues, a facile yet effective strategy of introducing hydroiodic acid (HI) into the synthesis procedure is established to achieve high-quality QDs and devices. Through an in-depth experimental analysis, the introduction of HI was found to convert PbI2 into highly coordinated [PbIm]2−m, enabling control of the nucleation numbers and growth kinetics. Combined optical and structural investigations illustrate that such a synthesis technique is beneficial for achieving enhanced crystallinity and a reduced density of crystallographic defects. Finally, the effect of HI is further reflected on the PV performance. The optimal device demonstrated a significantly improved power conversion efficiency of 15.72% along with enhanced storage stability. This technique illuminates a novel and simple methodology to regulate the formed species during synthesis, shedding light on further understanding solar cell performance, and aiding the design of future novel synthesis protocols for high-performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

Even the most efficient inverted p–i–n architecture perovskite solar cells (PSCs) are still inferior to those with regular n–i–p architecture, which is mainly limited by interfacial loss. Herein, both wet and dry metal–halide perovskite films are regulated through organic molecules–assisted sequential interfacial engineering for high‐performance inverted PSCs. In specific, organic acetic acid treatment on the wet film potently regulates the nucleation and crystallization of perovskite films. Then, further loading 4‐(dimethylamino)benzoic acid on the dry perovskite film creates a passivating agent layer to suppress defect formation, leading to more phase‐pure and conductive perovskite films. Combined experimental and theoretical results illustrate that such sequential treatment is beneficial for decreasing surface trap states, non‐radiative recombination, and carrier transport loss. As a result, the target inverted PSC exhibits an unprecedented high fill factor (FF) of 85.31% together with a champion efficiency of 21.37%, which is greatly improved relative to the reference (FF of 79.60%, and efficiency of 19.40%). It should be noted that such a high FF is among the highest report and corresponding to 94.38% of the Shockley–Queisser limited FF (90.39%) of PSCs with a bandgap of 1.576 eV. In addition, the storage stability against moisture of target inverted PSCs is remarkably enhanced. [ABSTRACT FROM AUTHOR]

The energy disorder originating from quantum dot (QD) size and relevant solid film inhomogeneity is detrimental to the charge transport and efficiency of QD based solar cells. The emergence of halide perovskite QDs (PQDs) have attracted great attention as promising absorbers in QD photovoltaics. However, it is currently difficult in preparing structural uniform PQD film with homogenous energetic landscape, which is essential for highly reproducible and efficient solar cells. Herein, assisted by a bidentate ligand 2,5‐thiophenedicarboxylic acid, a facile solution phase anchoring (SPA) strategy is first reported for design and preparation of all‐inorganic CsPbI3 PQD film with reduced structure and energy disorder. The SPA can enhance PQD dispersion as well as dot‐to‐dot interaction, which is beneficial for fabricating high‐quality PQD arrays and photovoltaic devices. The engineered CsPbI3 PQD solar cell exhibits enhanced reproducibility, and higher open–circuit voltage together with a champion efficiency of 16.14%, which is among the highest report to date. These results are believed to provide design principle of uniform PQDs for high‐performance optoelectronic application. [ABSTRACT FROM AUTHOR]

For emerging perovskite quantum dots (QDs), understanding the surface features and their impact on the materials and devices is becoming increasingly urgent. In this family, hybrid FAPbI3 QDs (FA: formamidium) exhibit higher ambient stability, near‐infrared absorption and sufficient carrier lifetime. However, hybrid QDs suffer from difficulty in modulating surface ligand, which is essential for constructing conductive QD arrays for photovoltaics. Herein, assisted by an ionic liquid formamidine thiocyanate, we report a facile surface reconfiguration methodology to modulate surface and manipulate electronic coupling of FAPbI3 QDs, which is exploited to enhance charge transport for fabricating high‐quality QD arrays and photovoltaic devices. Finally, a record‐high efficiency approaching 15 % is achieved for FAPbI3 QD solar cells, and they retain over 80 % of the initial efficiency after aging in ambient environment (20–30 % humidity, 25 °C) for over 600 h. [ABSTRACT FROM AUTHOR]

Ruddlesden–Popper phase 2D perovskite solar cells (PSCs) exhibit improved lifetime while still facing challenges such as phase alignment and up‐scaling to module‐level devices. Herein, polyelectrolytes are explored to tackle this issue. The contact between perovskite and hole‐transport layer (HTL) is important for decreasing interfacial non‐radiative recombination and scalable fabrication of uniform 2D perovskite films. Through exploring compatible butylamine cations, we first demonstrate poly(3‐(4‐carboxybutyl)thiophene‐2,5‐diyl)‐butylamine (P3CT‐BA) as an efficient HTL for 2D PSCs due to its great hydrophilicity, relatively high hole mobility and uniform surface. More importantly, the tailored P3CT‐BA has an anchoring effect and acts as the buried passivator for 2D perovskites. Consequently, a best efficiency approaching 18 % was achieved and we further first report large‐area (2×3 cm2, 5×5 cm2) 2D perovskite minimodules with an impressive efficiency of 14.81 % and 11.13 %, respectively. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid lead halide perovskite solar cells have made unprecedented progress in improving photovoltaic efficiency during the past decade, while still facing critical stability challenges. Herein, the natural organic dye Indigo is explored for the first time to be an efficient molecular passivator that assists in the preparation of high‐quality hybrid perovskite film with reduced defects and enhanced stability. The Indigo molecule with both carbonyl and amino groups can provide bifunctional chemical passivation for defects. In‐depth theoretical and experimental studies show that the Indigo molecules firmly binds to the perovskite surfaces, enhancing the crystallization of perovskite films with improved morphology. Consequently, the Indigo‐passivated perovskite film exhibits increased grain size with better uniformity, reduced grain boundaries, lowered defect density, and retarded ion migration, boosting the device efficiency up to 23.22%, and ≈21% for large‐area device (1 cm2). Furthermore, the Indigo passivation can enhance device stability in terms of both humidity and thermal stress. These results provide not only new insights into the multipassivation role of natural organic dyes but also a simple and low‐cost strategy to prepare high‐quality hybrid perovskite films for optoelectronic applications based on Indigo derivatives. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbX3 (X = Cl, Br, I, or mixed halides) perovskite quantum dots (QDs) exhibit tunable optical bandgaps and narrow emission peaks, which have received worldwide interest in the field of both photovoltaics (PVs) and light‐emitting diodes (LEDs). Herein, it is reported a discovery that CsPbI3 perovskite QD solar cell can simultaneously deliver high PV performance and intense electroluminescence. In specific, the multifunctional CsPbI3 QD film is fabricated through a simple yet efficient solid‐state‐ligand exchange process using a tailored organic ligand triphenyl phosphite (TPPI). The function of QD surface manipulation using TPPI here is proven to be twofold, balancing the carrier transport and effectively passivating the QD surface to produce conductive and emissive QD film. The CsPbI3 perovskite QD solar cell delivers a champion efficiency of 15.21% with improved open circuit voltage and high fill factor. Concurrently functioning as a red LED, the CsPbI3 perovskite QD solar cell outputs electric power to light conversion efficiency approaching 4%, a record value for QD electroluminescent PVs. The results here indicate that these versatile perovskite QDs may be a promising candidate for fabricating multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

Here, a pseudo-solution-phase ligand exchange (p-SPLE) strategy is developed for fabricating a CsPbI3 quantum dot (QD) solar cell. Using short organic aromatic ligands to partly replace the long-chain ligands in a QD solution, the p-SPLE treated CsPbI3 QD solar cell had an enhanced power conversion efficiency of up to 14.65% together with improved stability. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid film using conjugated materials and quantum dots (QDs) are of great interest for solution‐processed optoelectronic devices, including photovoltaics (PVs). However, it is still challenging to fabricate conductive hybrid films to maximize their PV performance. Herein, for the first time, superior PV performance of hybrid solar cells consisting of CsPbI3 perovskite QDs and Y6 series non‐fullerene molecules is demonstrated and further highlights their importance on hybrid device design. In specific, a hybrid active layer is developed using CsPbI3 QDs and non‐fullerene molecules, enabling a type‐II energy alignment for efficient charge transfer and extraction. Additionally, the non‐fullerene molecules can well passivate the QDs, reducing surface defects and energetic disorder. The champion CsPbI3 QD/Y6‐F hybrid device has a record‐high efficiency of 15.05% for QD/organic hybrid PV devices, paving a new way to construct solution‐processable hybrid film for efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

Lead‐halide perovskite quantum dots (QDs) have attracted substantial attention due to their great potential in solution‐processed optoelectronic applications. The current synthetic method mostly relies on the binary‐precursor strategy, which significantly restricts the reaction yield and elemental regulation, leading to extremely high material cost. Herein, a more versatile ternary‐precursor method to investigate the effect of the precursor ratios on the synthetic production, surface chemistry, and photovoltaic performance of CsPbI3 QDs is explored. It is revealed that a decreased Pb/Cs feeding ratio can largely increase the reaction yield, whereas a reduced Pb/I ratio can improve the surface termination and optical properties of the resultaning CsPbI3 QDs. After rational tuning of the synthetic protocol, the reaction yield can be improved more than 7.5 times and the material cost can be reduced from 303 $ g−1 to as low as 42 $ g−1 compared to the conventional binary‐precursor method. In addition, the photovoltaic device using these QDs exhibits an efficiency close to the reported state‐of‐the‐art ones. It is believed that this scalable and low‐cost preparation of CsPbI3 QDs provides new insight into the future commercialization of perovskite QDs‐based optoelectronics. [ABSTRACT FROM AUTHOR]

Keywords: 2D Perovskites; Polyelectrolytes; Ruddelsden-Popper Phase; Solar Cells EN 2D Perovskites Polyelectrolytes Ruddelsden-Popper Phase Solar Cells 1 1 1 09/01/22 20220905 NES 220905 B Eine Polyelektrolyt-Lochtransportschicht b für 2D-Perowskit-Solarzellen unter Verwendung eines kompatiblen Butylamin-Kations wurde von Jianyu Yuan und Mitarbeitern in ihrem Forschungsartikel untersucht (e202205111). Rücktitelbild: Tailoring Phase Alignment and Interfaces via Polyelectrolyte Anchoring Enables Large-Area 2D Perovskite Solar Cells (Angew. 2D Perovskites, Polyelectrolytes, Ruddelsden-Popper Phase, Solar Cells. [Extracted from the article]

Back Cover: Tailoring Phase Alignment and Interfaces via Polyelectrolyte Anchoring Enables Large-Area 2D Perovskite Solar Cells (Angew. 2D Perovskites, Polyelectrolytes, Ruddelsden-Popper Phase, Solar Cells The tailored polyelectrolyte has an anchoring effect and acts as a passivator for 2D perovskites, which can improve 2D perovskite phase alignment and interfacial charge transfer efficiency, and finally enables high-efficiency and large-area 2D perovskite solar cells. [Extracted from the article]

Keywords: CsPbI 3; non-fullerene molecules; organic-inorganic hybrid solar cells; perovskite quantum dots EN CsPbI 3 non-fullerene molecules organic-inorganic hybrid solar cells perovskite quantum dots 1 1 1 07/05/21 20210702 NES 210702 In article number 2101272, Jianyu Yuan and co-workers report an efficient quantum dots (QDs)/organic hybrid system using emerging CsPbI SB 3 sb QDs and narrow bandgap Y6 series non-fullerene acceptors. Non-Fullerene Molecules: Hybrid Perovskite Quantum Dot/Non-Fullerene Molecule Solar Cells with Efficiency Over 15% (Adv. Funct. CsPbI 3, non-fullerene molecules, organic-inorganic hybrid solar cells, perovskite quantum dots. [Extracted from the article]

Surface manipulation of quantum dots (QDs) has been extensively reported to be crucial to their performance when applied into optoelectronic devices, especially for photovoltaic devices. In this work, an efficient surface passivation method for emerging CsPbI3 perovskite QDs using a variety of inorganic cesium salts (cesium acetate (CsAc), cesium idodide (CsI), cesium carbonate (Cs2CO3), and cesium nitrate (CsNO3)) is reported. The Cs‐salts post‐treatment can not only fill the vacancy at the CsPbI3 perovskite surface but also improve electron coupling between CsPbI3 QDs. As a result, the free carrier lifetime, diffusion length, and mobility of QD film are simultaneously improved, which are beneficial for fabricating high‐quality conductive QD films for efficient solar cell devices. After optimizing the post‐treatment process, the short‐circuit current density and fill factor are significantly enhanced, delivering an impressive efficiency of 14.10% for CsPbI3 QD solar cells. In addition, the Cs‐salt‐treated CsPbI3 QD devices exhibit improved stability against moisture due to the improved surface environment of these QDs. These findings will provide insight into the design of high‐performance and low‐trap‐states perovskite QD films with desirable optoelectronic properties. [ABSTRACT FROM AUTHOR]

ZnO coupled Bi-doped porous LaFeO 3 nanocomposites have successfully been fabricated via a wet-chemical method. It is confirmed that Bi 3+ enters into the crystal lattice of PLFO and substitute La 3+ , while the ZnO with diameter of ∼15 nm is coupled to the Bi-doped PLFO. It is shown that the amount-optimized 5Zn/7Bi-PLFO nanocomposite exhibits greatly improved visible-light activities for 2,4-dichlorophenol (2,4-DCP) degradation and CO 2 conversion, compared to the unmodified PLFO with rather high photoactivity due to its large specific surface area. Based on the measurements of valence band XPS spectra, steady-state surface photovoltage spectra, transient-state surface photovoltage responses, photoelectrochemical I–V curves, fluorescence spectra related to produced OH amount and photocurrent action spectra, it is clearly demonstrated that the significantly improved visible-light activities are attributed to the enhanced utilization of visible-light-excited high-level-energy electrons (HLEEs) by coupling with nanocrystalline ZnO to introduce a new energy platform for accepting electrons and to the extended visible-light absorption by doping Bi 3+ to create surface states. Interestingly, it is proved that under UV–vis irradiation, the amount-optimized nanocomposite exhibit much higher photoactivity for 2,4-DCP degradation compared to the commercially available P25 TiO 2 . Moreover, it is confirmed by means of radical trapping experiments that the dominant radicals to decompose 2,4-DCP on PLFO could be modulated by doping Bi 3+ and coupling ZnO. Furthermore, the possible decomposition pathways, respectively related to the OH and O 2 − , of 2,4-DCP over the amount-optimized Bi-doped PLFO and ZnO coupled Bi-doped PLFO samples are proposed by means of the liquid chromatography tandem mass spectrometry analysis of the intermediates, especially with the used isotopic D 2 O. [ABSTRACT FROM AUTHOR]

In this work, TiO2-coupled N-doped porous perovskite-type LaFeO3 nanocomposites as highly efficient, cheap, stable, and visible-light photocatalysts have successfully been prepared via wet chemical processes. It is shown that the amount-optimized nanocomposite exhibits exceptional visible-light photocatalytic activities for 2,4-dichlorophenol (2,4-DCP) degradation by ∼3-time enhancement and for CO2 conversion to fuels by ∼4-time enhancement, compared to the resulting porous LaFeO3 with rather high photoactivity due to its large surface area. It is clearly demonstrated, by means of various experimental data, especially for the ·OH amount evaluation, that the obviously enhanced photoactivities are attributed to the increased specific surface area by introducing pores, to the extended visible-light absorption by doping N to create surface states, and to the promoted charge transfer and separation by coupling TiO2. Moreover, it is confirmed from radical trapping experiments that the photogenerated holes are the predominant oxidants in the photocatalytic degradation of 2,4-DCP. Furthermore, a possible photocatalytic degradation mechanism for 2,4-DCP is proposed mainly based on the resultant crucial intermediate, 2-chlorosuccinic acid withm/z = 153, that readily transform into CO2 and H2O. This work opens up a new feasible route to synthesize visible-light-responsive high-activity perovskite-type nanophotocatalysts for efficient environmental remediation and energy production. [ABSTRACT FROM AUTHOR]