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Hybrid inorganic-organic perovskites have attracted considerable attention over recent years as promising processable electronic materials. In particular, the rich structural dynamics of these ‘soft’ materials has become a subject of investigation and debate due to their direct influence on the perovskites' optoelectronic properties. Significant effort has focused on understanding the role and behaviour of the organic cations within the perovskite, as their rotational dynamics may be linked to material stability, heterogeneity and performance in (opto)electronic devices. To this end, we use two-dimensional IR spectroscopy (2DIR) to understand the effect of partial caesium alloying on the rotational dynamics of the methylammonium cation in the archetypal hybrid perovskite CH3NH3PbI3. We find that caesium incorporation primarily inhibits the slower ‘reorientational jump’ modes of the organic cation, whilst a smaller effect on the fast ‘wobbling time’ may be due to distortions and rigidisation of the inorganic cuboctahedral cage. 2DIR centre-line-slope analysis further reveals that while static disorder increases with caesium substitution, the dynamic disorder (reflected in the phase memory of the N-H stretching mode of methylammonium) is largely independent of caesium addition. Our results contribute to the development of a unified model of cation dynamics within organohalide perovskites.

In this work, we develop a photocatalyst wherein nitrogen and phosphorus co-doped carbon quantum dots are scaffolded onto TiO2 nanoparticles (NPCQD/TiO2), denoted as NPCT hereafter. The developed NPCT photocatalyst exhibits an enhanced visible light photocatalytic hydrogen production of 533 μmol h−1 g−1 compared to nitrogen doped CQD/TiO2 (478 μmol h−1 g−1), phosphorus doped CQD/TiO2 (451 μmol h−1 g−1) and pure CQD/TiO2 (427 μmol h−1 g−1) photocatalysts. The enhanced photocatalytic activity of the NPCT photocatalyst is attributed to the excellent synergy between NPCQDs and TiO2 nanoparticles, which results in the creation of virtual energy levels, a decrease in work function and suppressed recombination rates, thereby increasing the lifetime of photogenerated electrons. A detailed mechanism is proposed for the enhancement in visible light hydrogen production by the NPCT photocatalyst from the experimental results, Mott–Schottky plots and ultraviolet photoelectron spectroscopy results. Further, first-principles density functional theory (DFT) simulations are carried out which predict the decrease in the work function and band gap, and the increase in the density of states of NPCT as the factors responsible for the observed enhancement in visible light photocatalytic hydrogen production.

Funder: Ministry of Education; Id: http://dx.doi.org/10.13039/100010002, Although Cs2AgBiBr6 halide elpasolites have gained substantial attention as potential nontoxic and stable alternatives to lead–halide perovskites, they are limited by their wide bandgaps >2.2 eV. Alloying with Sb into the pnictogen site has been shown to be an effective method to lower the bandgap, but this has not translated into improvements in photovoltaic (PV) performance. Herein, the underlying causes are investigated. Pinhole‐free films of Cs2Ag(Sb x Bi1−x)Br6 are achieved through antisolvent dripping, but PV devices still exhibit a reduction in power conversion efficiency from 0.44% ± 0.02% (without Sb) to 0.073% ± 0.007% (90% Sb; lowest bandgap). There is a 0.7 V reduction in the open‐circuit voltage, which correlates with the appearance of a sub‐bandgap state ≈0.7 eV below the optical bandgap in the Sb‐containing elpasolite films, as found in both absorbance and photoluminescence measurements. Through detailed Williamson–Hall analysis, it is found that adding Sb into the elpasolite films leads to an increase in film strain. This strain is relieved through aerosol‐assisted solvent treatment, which reduces both the sub‐bandgap state density and energetic disorder in the films, as well as reducing the fast early decay in the photogenerated carrier population due to trap filling. This work shows that Sb alloying leads to the introduction of extra sub‐bandgap states that limit the PV performance, but can be mitigated through post‐annealing treatment to reduce disorder and strain.

Photoelectrochemical (PEC) artificial leaves hold the potential to lower the costs of sustainable solar fuel production by integrating light harvesting and catalysis within one compact device. However, current deposition techniques limit their scalability1, whereas fragile and heavy bulk materials can affect their transport and deployment. Here we demonstrate the fabrication of lightweight artificial leaves by employing thin, flexible substrates and carbonaceous protection layers. Lead halide perovskite photocathodes deposited onto indium tin oxide-coated polyethylene terephthalate achieved an activity of 4,266 µmol H2 g-1 h-1 using a platinum catalyst, whereas photocathodes with a molecular Co catalyst for CO2 reduction attained a high CO:H2 selectivity of 7.2 under lower (0.1 sun) irradiation. The corresponding lightweight perovskite-BiVO4 PEC devices showed unassisted solar-to-fuel efficiencies of 0.58% (H2) and 0.053% (CO), respectively. Their potential for scalability is demonstrated by 100 cm2 stand-alone artificial leaves, which sustained a comparable performance and stability (of approximately 24 h) to their 1.7 cm2 counterparts. Bubbles formed under operation further enabled 30-100 mg cm-2 devices to float, while lightweight reactors facilitated gas collection during outdoor testing on a river. This leaf-like PEC device bridges the gulf in weight between traditional solar fuel approaches, showcasing activities per gram comparable to those of photocatalytic suspensions and plant leaves. The presented lightweight, floating systems may enable open-water applications, thus avoiding competition with land use.

Funder: Royal Society; Id: http://dx.doi.org/10.13039/501100000288, We report here fast A‐site cation cross‐exchange between APbX3 perovskite nanocrystals (NCs) made of different A‐cations (Cs (cesium), FA (formamidinium), and MA (methylammonium)) at room temperature. Surprisingly, the A‐cation cross‐exchange proceeds as fast as the halide (X=Cl, Br, or I) exchange with the help of free A‐oleate complexes present in the freshly prepared colloidal perovskite NC solutions. This enabled the preparation of double (MACs, MAFA, CsFA)‐ and triple (MACsFA)‐cation perovskite NCs with an optical band gap that is finely tunable by their A‐site composition. The optical spectroscopy together with structural analysis using XRD and atomically resolved high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and integrated differential phase contrast (iDPC) STEM indicates the homogeneous distribution of different cations in the mixed perovskite NC lattice. Unlike halide ions, the A‐cations do not phase‐segregate under light illumination.

Colloidal lead-halide perovskite nanocrystals (LHP NCs) have emerged over the past decade as leading candidates for efficient next-generation optoelectronic devices, but their properties and performance critically depend on how they are purified. While antisolvents are widely used for purification, a detailed understanding of how the polarity of the antisolvent influences the surface chemistry and composition of the NCs is missing in the field. Here, we fill this knowledge gap by studying the surface chemistry of purified CsPbBr

Carlo A.R. Perini is a post-doctoral researcher at Georgia Institute of Technology, Energy Materials Lab. His studies focus on the development and understanding of interface passivation of 3D metal halide perovskites using vapor deposition routes. He has a PhD in Physics at Politecnico di Milano, in collaboration with the Italian Institute of Technology (IIT), focused on the study of energy efficient, scalable, and environmentally friendly deposition routes for lead halide perovskites. Tiarnan A. S. Doherty is a PhD student in the Cavendish laboratory at the University of Cambridge working on nanoscale structure property relationships in metal-halide perovskites. He received the gold graduate student award at the Fall Materials Research Society meeting. Samuel D. Stranks is a University Lecturer in Energy and Royal Society University Research Fellow at the University of Cambridge. His group's research focuses on the optical and electronic properties of emerging semiconductors for low-cost, transformative electronics applications including light-harvesting (e.g., photovoltaic) and light-emission (e.g., LED) devices. He received the 2018 Henry Moseley Award and Medal from the Institute of Physics, the 2019 Marlow Award from the Royal Society of Chemistry, and is a co-founder of Swift Solar, a startup developing lightweight perovskite PV panels. Juan-Pablo Correa-Baena is an Assistant Professor and Goizueta Junior Faculty Chair in the School of Materials Science and Engineering at Georgia Institute of Technology. His group focuses on the understanding and control of electronic dynamics at the nanoscale for low-cost semiconductors, such as halide perovskites. He completed his PhD at the University of Connecticut, followed by a postdoctoral fellowship at EPFL, Switzerland, then a US Department of Energy postdoctoral fellowship at MIT, USA. Robert L. Z. Hoye is a Lecturer (Assistant Professor) at Imperial College London. He leads the Energy Materials and Devices group, which is working on developing defect-tolerant semiconductors and their application in optoelectronic devices. This includes tandem photovoltaics, indoor solar cells, and light-emitting diodes. Robert has received the Young Engineer of the Year Award from the Royal Academy of Engineering, the Sir Henry Royce Medal from the Institution of Engineering and Technology, and the Rising Star Award from the Waterloo Institute for Nanotechnology.

Layered binary semiconductor materials have attracted significant interest as field emitters due to their low work function, mechanical stability, high thermal and electrical conductivity. Herein, we report a systematic experimental and theoretical investigation of SnS nanoflakes synthesized using a simple, low-cost, and non-toxic hot injection method for field emission studies. The field emission studies were carried out on SnS nanoflakes thin film prepared using a simple spin coat technique. The x-ray diffraction (XRD) and Raman spectroscopy analysis revealed an orthorhombic phase of SnS. Scanning electron microscopy (SEM) analysis revealed that as-synthesized SnS has flakes-like morphology. The formation of pure-phase SnS nanoflakes was further confirmed by x-ray photoelectron spectroscopy (XPS) analysis. The UV-Visible-NIR spectroscopy analysis shows that SnS nanoflakes have a sharp absorption edge observed in the UV region and have a band gap of ∼ 1.66 eV. In addition, the first-principles density functional theory (DFT) calculations were carried out to provide atomic-level insights into the crystal structure, band structure, and density of states (DOS) of SnS nanoflakes. The field emission properties of SnS nanoflakes were also investigated and found that SnS nanoflakes have a low turn-on field (∼ 6.2 V/μm for 10 μA/cm2), high emission current density (∼ 104 μA/cm2 at 8.0 V/μm), superior current stability (∼ 2.5 hrs for ∼ 1 μA) and a high field enhancement factor of 1735. The first principle calculations the predicted lower work function of different surfaces, especially for the most stable SnS (001) surface ( = 4.32 eV), is believed to be responsible for the observed facile electron emission characteristics. We anticipate that the SnS could be utilized for future vacuum nano/microelectronic and flat panel display applications due to the low turn-on field and flakes-like structure.

Funder: Helmholtz Young Investigator Group Frontrunner, Over the past few years, lead‐halide perovskites (LHPs), both in the form of bulk thin films and colloidal nanocrystals (NCs), have revolutionized the field of optoelectronics, emerging at the forefront of next‐generation optoelectronics. The power conversion efficiency (PCE) of halide perovskite solar cells has increased from 3.8% to over 25.7% over a short period of time and is very close to the theoretical limit (33.7%). At the same time, the external quantum efficiency (EQE) of perovskite LEDs has surpassed 23% and 20% for green and red emitters, respectively. Despite great progress in device efficiencies, the photoactive phase instability of perovskites is one of the major concerns for the long‐term stability of the devices and is limiting their transition to commercialization. In this regard, researchers have found that the phase stability of LHPs and the reproducibility of the device performance can be improved by A‐site cation alloying with two or more species, these are named mixed cation (double, triple, or quadruple) perovskites. This review provides a state‐of‐the‐art overview of different types of mixed A‐site cation bulk perovskite thin films and colloidal NCs reported in the literature, along with a discussion of their synthesis, properties, and progress in solar cells and LEDs.

Perovskite solar cells (PSCs) with transparent electrodes can be integrated with existing solar panels in tandem configurations to increase the power conversion efficiency. A critical layer in semi-transparent PSCs is the inorganic buffer layer, which protects the PSC against damage when the transparent electrode is sputtered on top. The development of n-i-p structured semi-transparent PSCs has been hampered by the lack of suitable p-type buffer layers. In this work we develop a p-type CuOx buffer layer, which can be grown uniformly over the perovskite device without damaging the perovskite or organic hole transport layer. The CuOx layer has high hole mobility (4.3 ± 2 cm2 V-1 s-1), high transmittance (>95%), and a suitable ionization potential for hole extraction (5.3 ± 0.2 eV). Semi-transparent PSCs with efficiencies up to 16.7% are achieved using the CuOx buffer layer. Our work demonstrates a new approach to integrate n-i-p structured PSCs into tandem configurations, as well as enable the development of other devices that need high quality, protective p-type layers., EPSRC Department Training Partnership studentship (No: EP/N509620/1), as well as Bill Welland. T.N.H. acknowledges funding from the EPSRC Centre for Doctoral Training in Graphene Technology (No. EP/L016087/1) and the Aziz Foundation. W.-W.L. and J.L.M.-D. acknowledge support from the EPSRC (Nos.: EP/L011700/1, EP/N004272/10), and the Isaac Newton Trust (Minute 13.38(k)). M.N. and J.L.M.-D. acknowledge financial support from EPSRC (No. EP/P027032/1). S. D. S. acknowledges support from the Royal Society and Tata Group (UF150033). R.L.Z.H. acknowledges support from the Royal Academy of Engineering under the Research Fellowship scheme (No.: RF\201718\1701), the Centre of Advanced Materials for Integrated Energy Systems (EPSRC Grant No. EP/P007767/1), the Isaac Newton Trust (Minute 19.07(d)), and the Kim and Juliana Silverman Research Fellowship at Downing College, Cambridge.

Plasma‐enhanced atomic layer deposition was used to grow non‐stoichiometric nickel oxide thin films with low impurity content, high crystalline quality, and p‐type conductivity. Despite the non‐stoichiometry, the films retained the antiferromagnetic property of NiO.

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Colloidal metal-halide perovskite nanocrystals (MHP NCs) are gaining significant attention for a wide range of optoelectronics applications owing to their exciting properties, such as defect tolerance, near-unity photoluminescence quantum yield, and tunable emission across the entire visible wavelength range. Although the optical properties of MHP NCs are easily tunable through their halide composition, they suffer from light-induced halide phase segregation that limits their use in devices. However, MHPs can be synthesized in the form of colloidal nanoplatelets (NPls) with monolayer (ML)-level thickness control, exhibiting strong quantum confinement effects, and thus enabling tunable emission across the entire visible wavelength range by controlling the thickness of bromide or iodide-based lead-halide perovskite NPls. In addition, the NPls exhibit narrow emission peaks, have high exciton binding energies, and a higher fraction of radiative recombination compared to their bulk counterparts, making them ideal candidates for applications in light-emitting diodes (LEDs). This review discusses the state-of-the-art in colloidal MHP NPls: synthetic routes, thickness-controlled synthesis of both organic–inorganic hybrid and all-inorganic MHP NPls, their linear and nonlinear optical properties (including charge-carrier dynamics), and their performance in LEDs. Furthermore, the challenges associated with their thickness-controlled synthesis, environmental and thermal stability, and their application in making efficient LEDs are discussed. Agencia Estatal de Investigación https://doi.org/10.13039/501100011033 | Ref. PID2020‐117371RA‐I00 Xunta de Galicia https://doi.org/10.13039/501100010801 | Ref. ED431F2021/05 Royal Academy of Engineering https://doi.org/10.13039/501100000287 | Ref. RF∖201718∖1701 Ministerio de Ciencia e Innovación | Ref. RYC2018-026103-I Xunta de Galicia | Ref. GRC ED431C2020/09

Inorganic zero-dimensional perovskites, such as Cs4PbBr6, offer an underexplored opportunity to achieve efficient exciton formation and radiative recombination. In particular, the origin of sub-ban...

Photoelectrochemical (PEC) devices have been developed for direct solar fuel production but the limited stability of submerged light absorbers can hamper their commercial prospects.

Owing to their defect tolerance and phase stability, α-CsPbI3 colloidal quantum dots (CQDs) with high mobility and 80–95% photoluminescence quantum yield (PLQY) are promising candidates for next-ge...

This review paper critically analyzes the importance of monitoring the synthesis of plasmonic and optoelectronic materials to not only provide a mechanistic understanding of their nucleation and growth but also crucial kinetic insights to enable their future development. Light-interacting nanoparticles present strong size-properties relationships, such that size control is at the core of any synthetic development. However, conventional ex-situ characterization of these materials has heavily limited their development to simple trial-and-error approaches. Over the last decade or so, the development of in-situ and online characterization capabilities has transformed our understanding, triggering a number of mechanistic models. In addition, time-resolved data have been able to reveal the steps rate, even for phenomena taking place in the microsecond scale (i.e. nucleation) thanks to the use of micro flow reactors. However, the literature contains a few disagreements and inaccuracies, which we consider to be due to the general lack of attention and control on mixing (especially relevant when mixing time is comparable to the reaction time) and the presence of additives during synthesis (e.g. stabilizers). Finally, we believe that recent in-situ monitoring development coupled with careful reactor design brings unique opportunities to not only synthesize nanoparticles in a reproducible and controllable manner but also to use data-rich approaches for self-regulated and automated systems.

Funder: Priority Academic Program Development of Jiangsu Higher Education Institutions; Id: http://dx.doi.org/10.13039/501100012246, Funder: 111 Project; Id: http://dx.doi.org/10.13039/501100013314, Funder: Joint International Research Laboratory of Carbon‐Based Functional Materials and Devices, Funder: European Union; Id: http://dx.doi.org/10.13039/501100000780, The Internet of Things (IoT) provides everyday objects and environments with “intelligence” and data connectivity to improve quality of life and the efficiency of a wide range of human activities. However, the ongoing exponential growth of the IoT device ecosystem—up to tens of billions of units to date—poses a challenge regarding how to power such devices. This Progress Report discusses how energy harvesting can address this challenge. It then discusses how indoor photovoltaics (IPV) constitutes an attractive energy harvesting solution, given its deployability, reliability, and power density. For IPV to provide an eco‐friendly route to powering IoT devices, it is crucial that its underlying materials and fabrication processes are low‐toxicity and not harmful to the environment over the product life cycle. A range of IPV technologies—both incumbent and emerging—developed to date is discussed, with an emphasis on their environmental sustainability. Finally, IPV based on emerging lead‐free perovskite‐inspired absorbers are examined, highlighting their status and prospects for low‐cost, durable, and efficient energy harvesting that is not harmful to the end user and environment. By examining emerging avenues for eco‐friendly IPV, timely insight is provided into promising directions toward IPV that can sustainably power the IoT revolution.

The formidable rise of lead‐halide perovskite photovoltaics has energized the search for lead‐free perovskite‐inspired materials (PIMs) with related optoelectronic properties but free from toxicity limitations. The photovoltaic performance of PIMs closely depends on their defect tolerance. However, a comprehensive experimental characterization of their defect‐level parameters—concentration, energy depth, and capture cross‐section—has not been pursued to date, hindering the rational development of defect‐tolerant PIMs. While mainstream, capacitance‐based techniques for defect‐level characterization have sparked controversy in lead‐halide perovskite research, their use on PIMs is also problematic due to their typical near‐intrinsic character. This study demonstrates on four representative PIMs (Cs3Sb2I9, Rb3Sb2I9, BiOI, and AgBiI4) for which Photoinduced Current Transient Spectroscopy (PICTS) offers a facile, widely applicable route to the defect‐level characterization of PIMs embedded within solar cells. Going beyond the ambiguities of the current discussion of defect tolerance, a methodology is also presented to quantitatively assess the defect tolerance of PIMs in photovoltaics based on their experimental defect‐level parameters. Finally, PICTS applied to PIM photovoltaics is revealed to be ultimately sensitive to defect‐level concentrations

Funder: Xunta de Galicia; Id: http://dx.doi.org/10.13039/501100010801, Lead‐halide perovskites (LHPs), in the form of both colloidal nanocrystals (NCs) and thin films, have emerged over the past decade as leading candidates for next‐generation, efficient light‐emitting diodes (LEDs) and solar cells. Owing to their high photoluminescence quantum yields (PLQYs), LHPs efficiently convert injected charge carriers into light and vice versa. However, despite the defect‐tolerance of LHPs, defects at the surface of colloidal NCs and grain boundaries in thin films play a critical role in charge‐carrier transport and nonradiative recombination, which lowers the PLQYs, device efficiency, and stability. Therefore, understanding the defects that play a key role in limiting performance, and developing effective passivation routes are critical for achieving advances in performance. This Review presents the current understanding of defects in halide perovskites and their influence on the optical and charge‐carrier transport properties. Passivation strategies toward improving the efficiencies of perovskite‐based LEDs and solar cells are also discussed.

Photoelectrochemical (PEC) artificial leaves hold the potential to lower the costs of sustainable solar fuel production by integrating light harvesting and catalysis within one compact device. However, current deposition techniques limit their scalability

High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al2O3 passivation layer on the Cu2O channel, followed by vacuum annealing at 300 C. Detailed characterisation by TEM-EDX and XPS shows that the surface of Cu2O is reduced following Al2O3 deposition and indicates the formation of 1-2 nm thick CuAlO2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al2O3, leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state., Comment: 25 pages, 6 figures, full paper

High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu

Funder: Aziz Foundation, Funder: Downing College, Cambridge, Funder: Isaac Newton Trust; Id: http://dx.doi.org/10.13039/501100004815, Nickel oxide (NiO x ), a p‐type oxide semiconductor, has gained significant attention due to its versatile and tunable properties. It has become one of the critical materials in wide range of electronics applications, including resistive switching random access memory devices and highly sensitive and selective sensor applications. In addition, the wide band gap and high work function, coupled with the low electron affinity, have made NiO x widely used in emerging optoelectronics and p‐n heterojunctions. The properties of NiO x thin films depend strongly on the deposition method and conditions. Efficient implementation of NiO x in next‐generation devices will require controllable growth and processing methods that can tailor the morphological and electronic properties of the material, but which are also compatible with flexible substrates. In this review, we link together the fundamental properties of NiO x with the chemical processing methods that have been developed to grow the material as thin films, and with its application in electronic devices. We focus solely on thin films, rather than NiO x incorporated with one‐dimensional or two‐dimensional materials. This review starts by discussing how the p‐type nature of NiO x arises and how its stoichiometry affects its electronic and magnetic properties. We discuss the chemical deposition techniques for growing NiO x thin films, including chemical vapor deposition, atomic layer deposition, and a selection of solution processing approaches, and present examples of recent progress made in the implementation of NiO x thin films in devices, both on rigid and flexible substrates. Furthermore, we discuss the remaining challenges and limitations in the deposition of device‐quality NiO x thin films with chemical growth methods. image

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research. Ministerio de Ciencia e Innovación | Ref. RYC2018-026103-I Agencia Estatal de Investigación | Ref. CTQ2017-82711-P Ministerio de Economía y Competitividad | Ref. MDM-2015-0538 Agencia Estatal de Investigación | Ref. PID2019-107314RB-I00

Funder: Ministry of Education, Taiwan, Lead-halide perovskites have demonstrated astonishing increases in power conversion efficiency in photovoltaics over the last decade. The most efficient perovskite devices now outperform industry-standard multi-crystalline silicon solar cells, despite the fact that perovskites are typically grown at low temperature using simple solution-based methods. However, the toxicity of lead and its ready solubility in water are concerns for widespread implementation. These challenges, alongside the many successes of the perovskites, have motivated significant efforts across multiple disciplines to find lead-free and stable alternatives which could mimic the ability of the perovskites to achieve high performance with low temperature, facile fabrication methods. This Review discusses the computational and experimental approaches that have been taken to discover lead-free perovskite-inspired materials, and the recent successes and challenges in synthesizing these compounds. The atomistic origins of the extraordinary performance exhibited by lead-halide perovskites in photovoltaic devices is discussed, alongside the key challenges in engineering such high-performance in alternative, next-generation materials. Beyond photovoltaics, this Review discusses the impact perovskite-inspired materials have had in spurring efforts to apply new materials in other optoelectronic applications, namely light-emitting diodes, photocatalysts, radiation detectors, thin film transistors and memristors. Finally, the prospects and key challenges faced by the field in advancing the development of perovskite-inspired materials towards realization in commercial devices is discussed.

With the exponential rise in the market value and number of devices part of the Internet of Things (IoT), the demand for indoor photovoltaics (IPV) to power autonomous devices is predicted to rapidly increase. Lead‐free perovskite‐inspired materials (PIMs) have recently attracted significant attention in photovoltaics research, due to the similarity of their electronic structure to high‐performance lead‐halide perovskites, but without the same toxicity limitations. However, the capability of PIMs for indoor light harvesting has not yet been considered. Herein, two exemplar PIMs, BiOI and Cs3Sb2ClxI9‐x are examined. It is shown that while their bandgaps are too wide for single‐junction solar cells, they are close to the optimum for indoor light harvesting. As a result, while BiOI and Cs3Sb2ClxI9‐x devices are only circa 1%‐efficient under 1‐sun illumination, their efficiencies increase to 4–5% under indoor illumination. These efficiencies are within the range of reported values for hydrogenated amorphous silicon, i.e., the industry standard for IPV. It is demonstrated that such performance levels are already sufficient for millimeter‐scale PIM devices to power thin‐film‐transistor circuits. Intensity‐dependent and optical loss analyses show that future improvements in efficiency are possible. Furthermore, calculations of the optically limited efficiency of these and other low‐toxicity PIMs reveal their considerable potential for IPV, thus encouraging future efforts for their exploration for powering IoT devices.

The easily tunable emission of halide perovskite nanocrystals throughout the visible spectrum makes them an extremely promising material for light-emitting applications. Whereas high quantum yields and long-term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind with low quantum yields, broad emission profiles, and insufficient colloidal stability. In this work, we present a facile synthetic approach for obtaining two-dimensional CsPbBr3 nanoplatelets with monolayer-precise control over their thickness, resulting in sharp photoluminescence and electroluminescence peaks with a tunable emission wavelength between 432 and 497 nm due to quantum confinement. Subsequent addition of a PbBr2-ligand solution repairs surface defects likely stemming from bromide and lead vacancies in a subensemble of weakly emissive nanoplatelets. The overall photoluminescence quantum yield of the blue-emissive colloidal dispersions is consequently enhanced up to a value of 73 ± 2%. Transient optical spectroscopy measurements focusing on the excitonic resonances further confirm the proposed repair process. Additionally, the high stability of these nanoplatelets in films and to prolonged ultraviolet light exposure is shown., Magdalene College, Cambridge

In methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs), the device performance is strongly influenced by the TiO2 elec-tron transport layer (ETL). Typically, the ETL needs to simultaneously be thin and pinhole-free in order to have high transmittance and avoid shunting. In this work, we develop an “in-situ solidification” process following spin coating, in which the titanium-based precursor (ti-tanium (diisopropoxide) bis (2,4-pentaneclionate)) is dried under vacuum to rapidly achieve continuous TiO2 layers. We refer to this as gas-phase quenching. This results in thin (60±10 nm), uniform and pinhole-free TiO2 films. The PSCs based on the gas-phase quenched TiO2 exhibits improved power conversion efficiency, with a median value of 18.23% (champion value of 20.43%), compared to 9.03% and 14.09% for the untreated devices. Gas-phase quenching is further shown to be effective in enabling efficient charge transfer at the MAPbI3/TiO2 heterointerface. Furthermore, the stability of the gas-phase quenched devices is enhanced in ambient air as well as under 1-sun illumination. In addition, we achieve 12.1% efficiency in upscaled devices (1.1 cm2 active area).

While extensively investigated in thin film form for energy materials applications, this work investigates the formation of APbBr3 structures (A = CH3NH3+ (MA), Cs+) in silicon and oxidized silicon nanotubes (SiNTs) with varying inner diameter. We carefully control the extent of oxidation of the nanotube host and correlate the relative Si/Si oxide content in a given nanotube host with the photoluminescence quantum efficiency (PLQE) of the perovskite. Complementing these measurements is an evaluation of average PL lifetimes of a given APbBr3 nanostructure, as evaluated by time-resolved confocal photoluminescence measurements. Increasing Si (decreasing oxide) content in the nanotube host results in a sensitive reduction of MAPbBr3 PLQE, with a concomitant decrease in average lifetime (τave). We interpret these observations in terms of decreased defect passivation by a lower concentration of oxide species surrounding the perovskite. In addition, we show that the use of selected nanotube templates leads to more stable perovskite PL in air over time (weeks). Taken in concert, such fundamental observations have implications for interfacial carrier interactions in tandem Si/perovskite photovoltaics.

While lead-based perovskites have held center stage in photovoltaic and optoelectronic research over the past decade, their toxicity has raised significant concerns, spurring the search for lead-free alternatives with similar potential. While a number of lead-free antimony-/bismuth-based compounds have been proposed, they have typically exhibited limited charge extraction efficiency, which has prompted the widespread adoption of a mesoporous device architecture. With a focus on compact films of Rb3Sb2I9—an emerging lead-free two-dimensional perovskite derivative—this study presents two strategies to enhance their microstructure: one relying on the reduction of the supersaturation level during the annealing step, and the other involving high-temperature annealing in an SbI3 atmosphere. Both strategies lead to a considerable improvement in film morphology and microstructure, with a twofold increase in apparent grain size. Such high-quality compact films deliver a pronounced rise in external quantum efficiency, as well as in short-circuit photocurrent under solar illumination—all this without the aid of a mesoporous architecture for charge extraction. Hall effect and photocurrent-power characterization show that this performance improvement results from an increase in charge carrier mobility and a reduction in the number of recombination centers. The microstructural improvement, photoconversion efficiency boost, and mechanistic insight provide valuable indications on the status and prospects of Rb3Sb2I9 and related derivatives—as relevant to the future exploration of these compounds for lead-free top-cells in tandem photovoltaics, indoor photovoltaics, and other optoelectronic application domains.