Michele Sessolo

• University of Valencia

Glasses are ubiquitous in our everyday lives but still pose fundamental questions about the nature of order in solids. Typically formed by the rapid cooling of a liquid, these amorphous solids have broad applications, with vitreous silica (SiO2) the most well-known example.1 Most functional glasses are purely inorganic solids, restricting the range...

The interfaces between the charge extraction layers and the perovskite layer are critical in defining the performance and stability of wide-bandgap (WBG) perovskite solar cells (PSCs). They govern multiple critical...

The efficiency of vacuum-processed perovskite solar cells lags behind that of solution-processed devices, partially because of the limited spectrum of deposition parameters that can be controlled during deposition. Substrate temperature is in principle a powerful tool to control the condensation and crystallization of thin films, but has been scarc...

Herein, we developed a simple approach for the fabrication of thin film inorganic perovskite and perovskite-related photoconductors. First, we synthesized CsPbBr3 and CsPb2Br5 nanoinks solutions under near-ambient conditions. Second, we...

Indium tin oxide (ITO) is the leading transparent electrode material in displays and in photovoltaics. As both these markets are vast and rapidly expanding, the demand for alternative transparent conductive oxides (TCOs) is becoming increasingly urgent due to the limited availability of indium. Herein, aluminum‐doped zinc oxide (AZO) is revisited a...

We investigate iodine migration in lead halide perovskite solar cells using X-ray photoelectron spectroscopy. We observe iodine migration to the surface direction at both the solar cell’s electrode and non-electrode regions. Our findings suggest that diffusion can drive iodine migration even without an electric field. We also detected iodine accumu...

One of the key topics in perovskite solar cells is the reduction of charge carrier recombination, with the aim of increasing power conversion efficiency. The recombination lifetime is a commonly used tool, as it directly affects the current–voltage curve via the diffusion length. The lifetime is often estimated using time‐domain measurement methods...

Organic light‐emitting diodes have a huge gain in popularity over the past 25 years for display and lighting applications, but the production of low‐cost efficient devices remains a challenge. OLEDs using sub‐nanometer undoped emissive layers are a route to fabricate cost‐effective devices but, as they are inherently thin, it opens to issues with v...

Metal halide perovskite photodiodes have garnered extensive attention owing to their favorable optoelectronic properties, rendering them attractive for visible, near‐infrared, and X‐ray sensors. However, their predominant reliance on solution‐processing deposition techniques poses challenges for seamless integration into existing industrial process...

Metal halide perovskites are promising semiconductors with promising applications in optoelectronic and photonic technologies. When coherent emission applications are targeted, materials with lower lasing thresholds and increased stabilities must be developed to increase the performance under continuous wave optical pumping condition and finally al...

The CsPbI3 perovskite has a suitable bandgap (≈1.7 eV) for application in tandem solar cells. One challenge for this compound is that the semiconducting perovskite phase is not stable at room temperature, when it tends to form a yellow nonperovskite phase with a bandgap of approximately 2.8 eV. Therefore, many reports have been focused on the stabi...

Coevaporation of perovskite films allows for a fine control over the material stoichiometry and thickness but is typically slow, leading to several-hour processes to obtain thick films required for photovoltaic applications. In this work, we demonstrate the coevaporation of perovskite layers using faster deposition rates, obtaining 1 μm thick films...

Bond breaking has emerged as a new tool to postsynthetically modify the pore structure in metal–organic frameworks since it allows us to obtain pore environments in structures that are inaccessible by other techniques. Here, we extend the concept of clip-off chemistry to archetypical ZIF-8, taking advantage of the different stabilities of the bonds...

Herein, a simple, solvent‐free method to fabricate polymer‐encapsulated halide perovskite photoconductors is described. Dry mechanochemical synthesis is used to prepare CsPbBr3 in the presence of poly(butyl methacrylate) (PBMA). The resulting composite powder is then heated and pressed into a free‐standing disk with a thickness controlled by a meta...

Lead halide perovskites have prompted great interest, offering impressive photovoltaic performances. Most fundamental investigations and cell optimizations focus on solution‐based solar cells, which are not easily extended to larger scales. Commonly in these cells, losses in the open‐circuit voltage are attributed to arise primarily from interface...

Electron transport layers (ETL) based on tin(IV) oxide (SnO2) are recurrently employed in perovskite solar cells (PSCs) by many deposition techniques. Pulsed laser deposition (PLD) offers a few advantages for the fabrication of such layers, such as being compatible with large scale, patternable, and allowing deposition at fast rates. However, a pre...

Wide bandgap perovskites are being widely studied in view of their potential applications in tandem devices and other semitransparent photovoltaics. Vacuum deposition of perovskite thin films is advantageous as it allows the fabrication of multilayer devices, fine control over thickness and purity, and it can be upscaled to meet production needs. H...

Fully evaporated solar cells using methylammonium iodide (MAI)‐based perovskites can reach power conversion efficiencies exceeding 20%. An important point to advance perovskite photovoltaics is to ensure reproducibility from batch to batch. Sublimation control of organic ammonium halides is critical in achieving this for evaporated perovskite solar...

Color discrimination and selective wavelength photodetection are crucial for many imaging applications. The most common method to achieve a narrowband spectral response is the combination of optical bandpass filters with...

The development of vacuum‐deposited perovskite materials and devices is partially slowed down by the minor research effort in this direction, due to the high cost of the required research tools. But there is also another factor, thermal co‐deposition in high vacuum involves the simultaneous sublimation of several precursors with an overall depositi...

Perovskite/perovskite tandem solar cells have recently exceeded the record power conversion efficiency (PCE) of single-junction perovskite solar cells. They are typically built in the superstrate configuration, in which the device is illuminated from the substrate side. This limits the fabrication of the solar cell to transparent substrates, typica...

Narrowband photodetectors (PDs) are sought after for many applications requiring selective spectral response. The most common systems combine optical bandpass filters with broadband photodiodes. This work reports a method to obtain a narrowband response in a perovskite PD by the monolithic integration of a perovskite photoconductor and a perovskite...

Metal halide perovskites have emerged as a promising group of materials for optoelectronic applications such as photovoltaics, light emission, and photodetectors. So-far, in particular, the stability of light-emitting devices is limited, which is in part attributed to the intrinsic ionic conductivity of these materials. High-performance devices ine...

Vacuum processing of multicomponent perovskites is not straightforward, because the number of precursors is in principle limited by the number of available thermal sources. Herein, we present a process which allows increasing the complexity of the formulation of vacuum-deposited lead halide perovskite films by multisource deposition and premixing b...

Vacuum processing is considered to be a promising method allowing the scalable fabrication of perovskite solar cells (PSCs). In vacuum processed PSCs, the n-i-p structure employing organic charge transport layers is less common than the p-i-n structure due to limited options to achieve an efficient electron extraction layer (EEL) on indium tin oxid...

Perovskite photodetectors are a promising technology for imaging applications, due to their high performance, tunable absorption spectrum and large area processability. New applications require devices with properties such as transparency,...

Thin polymeric and small‐molecular‐weight organic semiconductors are widely employed as hole transport layers (HTLs) in perovskite solar cells. To ensure ohmic contact with the electrodes, the use of doping or additional high work function (WF) interlayer is common. In some cases, however, intrinsic organic semiconductors can be used without any ad...

The syntheses and characterisations of a series of heteroleptic copper(I) compounds [Cu(POP)(Mebpy)][A], [Cu(POP)(Me2bpy)][A], [Cu(xantphos)(Mebpy)][A] and [Cu(xantphos)(Me2bpy)][A] in which [A]– is [BF4]–, [PF6]–, [BPh4]– and [BArF4]– (Mebpy = 6-methyl-2,2'-bipyridine, Me2bpy =...

Herein, the preparation of fully vacuum‐processed bismuth triiodide solar cells with low annealing temperature is reported. Planar n‐i‐p devices are prepared using a thin compact SnO2 layer as the electron extraction layer and an electron blocking/hole extraction bilayer consisting of an intrinsic and doped organic hole‐transport molecule. Using th...

Lead-free halide double perovskites (DPs) are highly tunable materials in terms of chemical composition and optical properties. One of the most widely reported DPs is Cs2AgBiBr6, which is envisaged as a promising absorber for photovoltaics. Nevertheless, its bandgap (around 1.9–2.3 eV) remains too large for common tandem solar cells. In this work,...

The choice of an adequate electrolyte is a fundamental aspect in polymer light-emitting electrochemical cells (PLECs) as it provides the in situ electrochemical doping and influences the performance of these devices. In this study, a hyperbranched polymer (Hybrane DEO750 8500) blended with a Li salt is used as a novel electrolyte in state-of-the-ar...

p>We report a series of seven cationic heteroleptic copper(I) complexes of the form [Cu (P^P) (dmphen)]BF₄, where dmphen is 2,9-dimethyl-1,10-phenanthroline and P^P is a diphosphine chelate, in which the effect of the bite angle of the diphosphine ligand on the photophysical properties of the complexes was studied. Several of the complex...

Vacuum deposition methods are increasingly applied to the preparation of perovskite films and devices, in view of the possibility to prepare multilayer structures at low temperature. Vacuum-deposited, wide-bandgap solar cells based on mixed-cation and mixed-anion perovskites have been scarcely reported, due to the challenges associated with the mul...

Herein, the long‐term stability of vacuum‐deposited methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs) with power conversion efficiencies (PCEs) of around 19% is evaluated. A low‐temperature atomic layer deposition (ALD) Al2O3 coating is developed and used to protect the MAPbI3 layers and the solar cells from environmental agents. Th...

Lead halides are used extensively to prepare perovskite-based devices but less known that lead halides can also form luminescent complexes in solvents. Using polyethylene glycol solvent, lead bromide complex with photoluminescent quantum yield over 20 % is obtained and photoluminescent peak can be shifted around 50 nm with alkylammonium bromides.

http://www.rsc.org/suppdata/d0/tc/d0tc04057f/d0tc04057f2.mp4

Fully inorganic cesium lead halide perovskites, such as CsPbI2Br, show enhanced thermal stability compared to hybrid ones and are being widely investigated as wide bandgap absorbers for tandem applications. Despite their simple stoichiometry, the preparation of highly crystalline and stable cesium lead halide thin films is not trivial. In general,...

Preparation of black formamidinium lead iodide (FAPbI3) requires high temperature annealing and the incorporation of smaller A-site cations, such as methylammonium (MA+), cesium or rubidium. A major advantage of vacuum processing is the possibility to deposit perovskite films at room temperature (RT), without any annealing step. Here we demonstrate...

In a short period of time rapid development of perovskite solar cells attracted a lot of attention in the science community with record for power conversion efficiency being broken every year. Despite the fast progress in power conversion efficiency there are still many issues that need to be solved before starting large scale commercial applicatio...

Halide perovskites have generated considerable research interest due to their excellent optoelectronic properties in the past decade. To ensure the formation of high quality semiconductors, the deposition process for the perovskite film is a critical issue. Vacuum based processing is considered a promising method allowing, in principle, also for la...

Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), 4,5,6-trimethyl-2,2′-bipyridine (4,5,6-Me3bpy), 6-(tert-butyl)-2,2′-bipyridine (6-tBubpy) and 2-ethyl-1,10-phenanthroline (2-Etphen) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP, PIN [oxydi(2,1-phenylene)]bis(diphenylphosphane)) or...

Herein the mechanochemical synthesis of inorganic as well as hybrid organic–inorganic monohalide perovskites with tunable bandgaps is reported. It is shown that the bandgap bowing known for iodide mixed Sn–Pb perovskites is also present in the pure bromide analogous. This results in technologically very interesting materials with bandgaps in the ra...

Herein we demonstrate the dry synthesis of CsBi3I10 both as free-standing material as well as in the form of homogeneous thin films, deposited by thermal vacuum deposition. Chemical and optical characterization shows high thermal stability, phase purity, and photoluminescence centered at 700 nm, corresponding to a bandgap of 1.77 eV. These characte...

A series of copper(I) complexes of the type [Cu(HN‐xantphos)(N^N)][PF6] and [Cu(BnN‐xantphos)(N^N)][PF6], in which N^N = bpy, Mebpy, and Me2bpy, HN‐xantphos = 4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine and BnN‐xantphos = 10‐benzyl‐4,6‐bis(diphenylphosphanyl)‐10H‐phenoxazine is described. The single crystal structures of [Cu(HN‐xantphos)(Mebpy)][PF...

In perovskite solar cells, the choice of appropriate transport layers and electrodes is of great importance to guarantee efficient charge transport and collection, minimizing recombination losses. The possibility to sequentially process multiple layers by vacuum methods offers a tool to explore the effects of different materials and their combinati...

The dual-source vacuum deposition of 2D perovskite films of the type PEA2PbX4, (PEA = phenetylammonium and X = I-, Br-, or a combination of both) is presented. Low-temperature deposited 2D perovskite films showed high crystallinity with the expected trend of bandgap as a function of halide type and concentration. Importantly, we observed an unavoid...

Hole transport layers (HTLs) are of fundamental importance in perovskite solar cells (PSCs), as they must ensure an efficient and selective hole extraction, and ohmic charge transfer to the corresponding electrodes. In p-i-n solar cells, the ITO/HTL is usually not ohmic, and an additional interlayer such as MoO3 is usually placed in between the two...

New cycloplatinated N-heterocyclic carbene (NHC) compounds with chelate diphosphines (P^P) as ancillary ligands: [Pt(R-C^C*)(P^P)]PF6 (R = H, P^P = dppm (1A), dppe (2A), dppbz (3A); R = CN, P^P = dppm (1B), dppe (2B), dppbz (3B)) have been prepared from the corresponding starting material [{Pt(R-C^C*)(μ-Cl)}2] (R = H, A, R = CN, B) and fully charac...

A simple method to obtain bright photoluminescent wide bandgap mixed‐halide 3D perovskites is reported. The materials are prepared by dry mechanochemical synthesis (ball‐milling) starting from neat binary precursors, and show enhanced photoluminescence upon the addition of an adamantane derivative in the precursors' mixture. The structural characte...

Non-toxic alternatives to lead halide perovskites are highly sought after for applications in optoelectronics. Blue-luminescent materials are espe-cially demanded as they could be used to prepare white light-emitting diodes, with important potential applications in lighting systems. Howev-er, wide bandgap blue emitters with high photoluminescence q...

Low-dimensional (quasi-) 2D perovskites are being extensively studied in order to enhance the stability and especially the open-circuit voltage (Voc) of perovskite solar cells. Up to no, thin 2D perovskite layers on the surface and/or at the grain boundaries of 3D perovskite have been deposited solely by solution processing, leading to unavoidable...

Electron-transport materials such as fullerene are widely used in perovskite solar cells to selectively transfer the photogenerated electrons to the electrodes. In order to minimize losses at the interface between the fullerene to the electrode, it is important to reduce the energy difference between the transport level of the two materials. A comm...

Chloride is extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI3–xClx), but its persistence and role in solution‐processed materials has not yet been rationalized. Multiple‐source vacuum deposition of perovskites enables a fine control over thin‐film stoichiometry and allows the incorporation of...

Herein, the dehydration of a hydrogen molybdenum bronze (HYMoO3), converting it to molybdenum oxide (MoOX), is explored toward the development of perovskite solar cells (PSCs) for the first time. H0.11MoO3 bronze is synthesized, characterized, and deposited on indium tin oxide (ITO) under different concentrations and annealing conditions for in sit...

Lead halide perovskites (ABX3) are generally formed from a reaction of the lead halide salt (BX2) with the halide salt of the A cation (AX). The effects of varying film compositions as result of non-stoichiometric precursor ratios on electronic properties of halide perovskites are currently under debate. It is imperative, but experimentally challen...

It is widely accepted that a long photoluminescence (PL) lifetime in metal halide perovskite films is a crucial and favorable factor, as it ensures a large charge diffusion length leading to a high power conversion efficiency (PCE) in solar cells. It has been recently found that vacuum-deposited (evaporated) methylammonium lead iodide (eMAPI) films...

Methylammonium lead triiodide (MAPI) has emerged as a high‐performance photovoltaic material. Common understanding is that at room temperature, it adopts a tetragonal phase and it only converts to the perfect cubic phase around 50–60 °C. Most MAPI films are prepared using a solution‐based coating process, yet they can also be obtained by vapor‐phas...

Phase‐pure CsSnI3, FASnI3, Cs(PbSn)I3, FA(PbSn)I3 perovskites (FA = formamidinium = HC(NH2)2⁺) as well as the analogous so‐called vacancy‐ordered double perovskites Cs2SnI6 and FA2SnI6 are mechanochemically synthesized. The addition of SnF2 is found to be crucial for the synthesis of Cs‐containing perovskites but unnecessary for hybrid ones. All co...

We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic-inorganic perovskite nanocrystals with low structural dimensionality. The emission wavelength of iodide-based perovskites is thus tuned from the near-infrared to the red part of the visible spectrum. While this is mostly ac...

A variety of experiments on vacuum deposited methylammonium lead iodide perovskite solar cells is presented, including IV curves with different scan rates, light intensity dependent open-circuit voltage, impedance spectra, intensity-modulated photocurrent spectra (IMPS), transient photocurrents and transient voltage step responses. All these experi...

A rigid dinuclear Ir(III) complex showing high photoluminescence quantum yield in pure films was successfully used to fabricate light-emitting electrochemical cells with and without ionic liquid additives. The devices showed nearly instantaneous electroluminescence after biasing and maximum quantum yield approaching 1%. The lifetime of the devices...

Vacuum-deposition of perovskite solar cells can achieve efficiencies rivalling solution-based methods and it allows for more complex device stacks. MoO3 has been used to enhance carrier extraction to the transparent bottom electrode in a p-i-n configuration, here we show that by inserting an organic charge transport molecule it can also be used on...

We have synthesized fifteen inorganic and hybrid organic-inorganic non-toxic A3Bi2X9 compounds (A = K+, Rb+, Cs+, CH3NH3+ and HC(NH2)2+; X = I-, Br-, Cl-) through dry mechanochemistry. We demonstrate that this synthetic method is very well suited to prepare compounds from poorly soluble precursors, allowing thus the preparation of so far unreported...

MoO3 is a good candidate to be used in perovskite solar cells due to its low lying conduction band and work function, along with a reduced parasitic absorption, which allows an optimal transport of holes. In order to introduce energy states for the charge transport it is necessary to create oxygen vacancies chemically or through an annealing step....

Potassium halides (KX; X = I, Br, or Cl) were incorporated as partial replacements of CsBr in the mechanosynthesis of CsPbBr3. This led to partial substitution of both monovalent ions forming mixed Cs1−xKxPbBr3−yXy perovskites. Longer photoluminescence lifetimes were also observed, possibly linked to the formation of a non-perovskite KPb2X5 passiva...

This chapter reviews the progress toward perovskite light‐emitting diodes (LEDs), highlighting the importance of developing high photoluminescence quantum yield (PLQY) perovskite materials and their incorporation into optimized multilayer light‐emitting devices. As for perovskite solar cells, the embodiment and materials of perovskite LEDs are anal...

Halide perovskites have shown excellent photophysical properties for solar cell applications which led to a rapid increase of the device efficiency. Understanding the charge carrier dynamics within the active perovskite absorber and at its interfaces will be key to further progress in their development. Here we present a series of fully evaporated...

Efficient organic light-emitting diodes (OLEDs) can be obtained using multilayer architectures where the processes of charge injection, transport and recombination are separated and optimized in each layer. Processing these structures from solution requires strategies to avoid redissolution or damage of the previously deposited layers. Several repo...

The synthesis and characterization of five [Cu(P^P)(N^N)][PF6] complexes in which P^P = 2,7-bis(tert-butyl)-4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (tBu2xantphos) or the chiral 4,5-bis(mesitylphenylphosphino)-9,9-dimethylxanthene (xantphosMes2) and N^N = 2,2'-bipyridine (bpy), 6-methyl-2,2'-bipyridine (6-Mebpy) or 6,6'-dimethyl-2,2'-bipyrid...

Efficient perovskite devices consist in a perovskite film sandwiched in between charge selective layers, in order to avoid non-radiative recombination. A common metal oxide used as p-type or hole transport layer is molybdenum oxide. MoO3 is of particular interest for its very large work function, which allows it to be used both as an interfacial ch...

Organic-inorganic metal halide perovskites are emerging as novel materials for light-emitting applications due to their high color purity, bandgap tunability, straightforward synthesis and inexpensive precursors. In this work, we improve the performance of 3D perovskite light-emitting diodes (PeLEDs) by tuning the emissive layer composition and thi...

Fully inorganic cesium lead halide perovskite thin films were prepared by an easy, fast and dry process based on single-source vacuum deposition. We investigated the structural and optical characteristics of the so-formed films as a function of chemical composition (chloride, bromide and iodide films were formed), post-deposition thermal annealing,...

The preparation and characterization of a series of iridium(III) ionic transition-metal complexes for application in light-emitting electrochemical cells (LECs) are reported. The complexes are of the type [Ir(C^N)2(N^N)][PF6] in which C^N is one of the cyclometallating ligands 2-(3-(tert-butyl)phenyl)pyridine (tppy), 2-phenylbenzo[d]thiazole (pbtz)...

A cross-linkable triazatruxene that leads to insoluble films upon thermal annealing at temperatures compatible with flexible substrates is presented. The films were used as the hole transporting and electron blocking layer in partially solution processed phosphorescent organic light-emitting diodes, reaching power conversion efficiencies of 24 lm W...

The recent success of perovskite solar cells is based on two solid pillars: the rapid progress of their power conversion efficiency and their flexibility in terms of optoelectrical properties and processing methods. That versatility makes these devices ideal candidates for multi-junction photovoltaics. We report an optically optimized double juncti...

Methylammonium lead iodide (MAPI) has excellent properties for photovoltaic applications, although it typically shows low photoluminescence quantum yield (PLQY). Here we report on vacuum-deposited MAPI perovskites obtained by modifying the MAI to PbI2 ratio during vacuum deposition. By studying the excitation density dependence of the photoluminesc...

We report a series of [Cu(P^P)(N^N)][PF6] complexes with P^P = bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) and N^N = 6-methoxy-2,2′-bipyridine (MeObpy), 6-ethoxy-2,2′-bipyridine (EtObpy), 6-phenyloxy-2,2′-bipyridine (PhObpy), 6-methylthio-2,2′-bipyridine (MeSbpy), 6-ethylthio-2,2′-bipyri...

Planar vacuum deposited p-i-n methyl ammonium lead tri-iodide perovskite solar cells are prepared with different electron and hole transporting layers, either doped or undoped. The effect of these layers on the solar cells performance (efficiency and stability) is studied. The main benefit of using doped layers lies in the formation of barrier free...