Mahui

Intrinsically conductive SrCo_0.95P_0.05O_3−δ (SCP) as a new platinum (Pt)‐free cathode in dye‐sensitized solar cells (DSSCs) is reported. SCP shows superior performance to that of the parent SrCoO_3−δ due to the greatly enhanced electrical conductivity and more internal conducting pathways. The DSSC with SCP/multiwalled carbon nanotubes cathode shows an attractive power conversion efficiency of 12.2%, which is 23% higher than the Pt cathode.

State‐of‐the‐art dye‐sensitized solar cells (DSSCs) usually use the noble and scarce platinum (Pt) cathode, which strongly limits the practical applications of DSSCs. Accordingly, low‐cost, highly active, and stable alternatives to Pt are highly desired. Herein, an intrinsically conductive perovskite oxide is reported as a new cathode for DSSCs using a simple nonmetal element doping strategy. The phosphorus‐doped perovskite oxide (SrCo_0.95P_0.05O_3−δ [SCP]) shows superior activity/durability for the triiodide (I₃ ⁻) reduction reaction (IRR) and structural stability relative to the parent compound (SrCoO_3−δ [SC]) due to the greatly enhanced electrical conductivity and the stabilization of the perovskite structure. The internal conducting pathways are demonstrated to be very important to obtain high IRR activity of the perovskite cathode, even when the cathode is incorporated with conductive multiwalled carbon nanotubes (MWCNTs). The DSSC with the N719 dye and SCP/MWCNTs cathode displays a superior power conversion efficiency (PCE) of 10.1% to those with Pt (8.11%) and SC/MWCNTs (6.80%) cathodes. In addition, the DSSC with the C101 dye and SCP/MWCNTs cathode shows an attractive PCE of 12.2% with an enhancement of 23%, as compared with the Pt cathode, suggesting that the SCP/MWCNTs composite can be one of the best substitutions to the Pt cathode, which can benefit the future industrialization of DSSCs.

The origins of defect tolerance in metal halide perovskites and the corresponding simulation results, and the impact of defects on both the performance and stability of perovskite‐based light‐emitting diodes (PeLEDs) are reviewed. In addition, an account of the defect‐passivation methods for improving the performance and stability of PeLEDs and future research directions for defect passivation are also presented.

Abstract

Metal halide perovskites (MHPs) have emerged as promising emitters because of their excellent optoelectronic properties, including high photoluminescence quantum yields (PLQYs), wide‐range color tunability, and high color purity. However, a fundamental limitation of MHPs is their low exciton binding energy, which results in a low radiative recombination rate and the dependence of PLQY on the excitation intensity. Under the operating conditions of light‐emitting diodes (LEDs), the injected current densities are typically lower than the trap density, leading to a low actual PLQY. Moreover, the defects not only initiate the decomposition of MHPs caused by extrinsic factors, but also intrinsically stimulate ion migration across the interface and lead to the corrosion of electrodes due to interaction between those electrodes, even under inert conditions. The passivation of defects has proven to be effective for mitigating the effects of defects in MHPs. Herein, the origins and theoretical calculations of the defect tolerance in MHPs and the impact of defects on both the performance and stability of perovskite LEDs are reviewed. The passivation methods and materials for MHP bulk films and nanocrystals are discussed in detail. Based on the currently reported advances, specific requirements and future research directions for display applications are suggested.

High‐performance perovskite resistive memory devices are made by employing a nonhalide lead source. The unipolar perovskite memory devices achieve an outstanding ON/OFF ratio with a relatively low operation voltage, a large endurance, and long retention times. The reliable fabrication of high‐yield cross‐bar array perovskite memory devices demonstrates the potential for realizing high‐density perovskite memory devices with excellent selectivity.

Abstract

Resistive random access memories can potentially open a niche area in memory technology applications by combining the advantages of the long endurance of dynamic random‐access memory and the long retention time of flash memories. Recently, resistive memory devices based on organo‐metal halide perovskite materials have demonstrated outstanding memory properties, such as a low‐voltage operation and a high ON/OFF ratio; such properties are essential requirements for low power consumption in developing practical memory devices. In this study, a nonhalide lead source is employed to deposit perovskite films via a simple single‐step spin‐coating method for fabricating unipolar resistive memory devices in a cross‐bar array architecture. These unipolar perovskite memory devices achieve a high ON/OFF ratio up to 10⁸ with a relatively low operation voltage, a large endurance, and long retention times. The high‐yield device fabrication based on the solution‐process demonstrated here will be a step toward achieving low‐cost and high‐density practical perovskite memory devices.

A water‐based TiO₂ nanocrystal solution is developed to use as an electron transport layer for perovskite solar cells that show substantially reduced organic molecules and a high Cl content on the TiO₂ nanocrystal surface, which effectively passivate the interface between TiO₂ and perovskite layer with significantly reduced defects. Corresponding solar cells demonstrate a 20.5% power conversion efficiency and 500 h of operational stability.

Halide perovskite solar cells (PSCs) provide a new opportunity for next‐generation photovoltaic applications. However, traditional low‐temperature solution‐processed TiO₂ that acts as an electron transport layer for PSCs shows an inferior stability compared with solar cells based on high‐temperature (typically 500 °C) TiO₂; however, the high‐temperature process is energy consuming and is not compatible with flexible device processing. Traditional TiO₂ nanoparticles made from titanium tetrachloride dispersed in an organic solvent usually have many organic molecules attached on their surface that lead to the formation of deep‐level defect states during long‐term operations. Herein, environmentally friendly, water‐based Cl‐passivated TiO₂ nanoparticles (W‐TiO₂) are invented, and surface organic molecules are removed by a vacuum rotary evaporation process. W‐TiO₂‐based PSCs can reach up to a 20.5% power conversion efficiency with reduced hysteresis and can maintain 80% of their initial performance after 500 h of continuous operation under 1 sun illumination at the maximum power point. This improved performance is ascribed to the organic‐molecule‐free and Cl‐passivated surfaces. The water‐based TiO₂ nanoparticle dispersion also offers a convenient and universal way to introduce other passivation agents to further improve the photovoltaic performance of PSCs.

A sulfur/nitrogen‐enriched polyimide (E‐PI) with high glass transition temperature (>200 °C) is synthesized and introduced as an interlayer for inverted‐type polymer:nonfullerene solar cells. The 3 nm‐thick E‐PI interlayers result in the improved efficiency and stability of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b″]dithiophene))‐alt‐(5,5‐(1″,3″‐di‐2‐thienyl‐5″,7″‐bis(2‐ethylhexyl)benzo[1″,2″‐c:4″,5″‐c″]dithiophene‐4,8‐dione))] (PBDB‐T):3,9‐bis(6‐methyl‐2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2″,3″‐d″]‐s‐indaceno[1,2‐b:5,6‐b″]dithiophene) solar cells due to the increased work function (electron mobility) of zinc oxide electron‐collecting buffer layers.

Herein, it is reported that sulfur/nitrogen‐enriched polyimide can act as a stable interlayer for inverted‐type polymer:nonfullerene solar cells because it improves the power conversion efficiency (PCE) and stability of the devices. The sulfur/nitrogen‐enriched polyimide (E‐PI) interlayers are prepared on the zinc oxide layers via the thermal imidization of corresponding films of soluble precursor polymer, poly(N‐(2‐((carboxymethyl)(2‐((5‴‐methyl‐[2,2″:5″,2″:5″,2‴‐quaterthiophen]‐5‐yl)amino)‐2‐oxoethyl)amino)ethyl)‐N‐(2‐(methylamino)‐2‐oxoethyl)glycine acid), which is synthesized from ethylenediaminetetraacetic dianhydride and 5,5‴‐diamino‐2,2″:5″,2″:5″,2‴‐quaterthiophene. The E‐PI films exhibit high glass transition temperature (≈204 °C) and broad optical absorption up to ≈1000 nm (absorption edge). Results show that the average PCE of polymer:nonfullerene solar cells is increased from 10.86% to 11.6% at the E‐PI thickness of 3 nm. In particular, the stability of polymer:nonfullerene solar cells is clearly improved by inserting the 3 nm‐thick E‐PI interlayers.

Nickel oxide (NiO _x ) as the most commonly used hole transport layer in inverted perovskite solar cells is doped by nitrogen for the first time, affording an obvious enhancement of average power conversion efficiency from 15.28% to 17.02%. This is primarily due to increased electrical conductivity and lowered valence band energy of the NiO _x film after nitrogen doping.

Nickel oxide (NiO _x ) is commonly used as a hole transport layer (HTL) in inverted‐structure (p‐i‐n) planar perovskite solar cells (PSCs), playing a critical role in the device performance. However, a solution‐processed NiO _x HTL usually suffers from low electrical conductivity, consequently resulting in an inefficient interfacial charge transport. Herein, a facile method is developed to prepare nitrogen‐doped NiO _x (N:NiO _x ), which is applied as a novel HTL in inverted PSCs for the first time, achieving a decent improvement in average power conversion efficiency (PCE) from 15.28% to 17.02%. The effects of nitrogen doping on the electrical conductivity and the energy band structure of NiO _x as well as the quality of CH₃NH₃PbI₃ perovskite layer atop are studied by a series of characterizations, revealing that nitrogen doping leads to increased electrical conductivity and lowered valence band energy of the NiO _x film, which are beneficial to interfacial hole transport. In addition, the trap density of the CH₃NH₃PbI₃ perovskite film atop N:NiO _x layer is reduced, prohibiting unfavorable charge recombination.

Low‐cost counter materials for dye‐sensitized and perovskite solar cells are summarized, with a focus on the regular patterns that appear in their intrinsic features and structural design.

Abstract

It is undoubtable that the use of solar energy will continue to increase. Solar cells that convert solar energy directly to electricity are one of the most convenient and important photoelectric conversion devices. Though silicon‐based solar cells and thin‐film solar cells have been commercialized, developing low‐cost and highly efficient solar cells to meet future needs is still a long‐term challenge. Some emerging solar‐cell types, such as dye‐sensitized and perovskite, are approaching acceptable performance levels, but their costs remain too high. To obtain a higher performance–price ratio, it is necessary to find new low‐cost counter materials to replace conventional precious metal electrodes (Pt, Au, and Ag) in these emerging solar cells. In recent years, the number of counter‐electrode materials available, and their scope for further improvement, has expanded for dye‐sensitized and perovskite solar cells. Generally regular patterns in the intrinsic features and structural design of counter materials for emerging solar cells, in particular from an electrochemical perspective and their effects on cost and efficiency, are explored. It is hoped that this recapitulative analysis will help to make clear what has been achieved and what still remains for the development of cost‐effective counter‐electrode materials in emerging solar cells.

The unstable properties of hybrid perovskites, such as crystal phase transition, fragmentation of organic molecules, and hydrogen bond dissociation, are reviewed, and the importance of additives in structurally stabilizing formamidinium lead trihalide in place of methylammonium is emphasized.

Abstract

Hybrid lead halide perovskite materials are used in solar cells and show efficiencies greater than 23%. Furthermore, they are applied in light‐emitting diodes, X‐ray detectors, thin‐film transistors, thermoelectrics, and memory devices. Lead trihalide hybrid materials contain methylammonium (MA) or formamidinium (FA) (or a mixture), or long alkylammonium halides, as alternative organic cations. However, the intrinsic stability of hybrid lead halide perovskites is not very high, and they are chemically unstable when exposed to moisture, light, or heat because of their organic contents and low formation energies. Therefore, although improvements in the chemical stability are crucial, changing the material composition is challenging because it is directly related to the desired application requirements. Fortunately, hybrid lead halide perovskites have a very high tolerance toward changes in physical properties arising from doping or addition of different cations and anions, in many cases showing improved properties. Here, the intrinsic instability of hybrid lead halide perovskites is reviewed in relation to the crystal phase and chemical stability. It is suggested that FA should be used for lead halide perovskites for chemical stability instead of MA. Furthermore, additives that stabilize the crystal phase with α‐FAPbI₃ should eschew MA.

The properties of excitons and photogenerated charge carriers in metal halide perovskites (MHPs) are explored. The properties of excitons including the exciton binding energy, exciton dynamics, and exciton–photon and exciton–phonon coupling, are discussed. The properties of photogenerated free charge carriers in MHPs such as diffusion length, mobility, and recombination are described. A brief review of recent applications is also demonstrated.

Abstract

Metal halide perovskites (MHPs) have recently attracted great attention from the scientific community due to their excellent photovoltaic performance as well as their tremendous potential for other optoelectronic applications such as light‐emitting diodes, lasers, and photodetectors. Despite the rapid progress in device applications, a solid understanding of the photophysical properties behind the device performance is highly desirable for MHPs. Here, the properties of excitons and photogenerated charge carriers in MHPs are explored. The unique dielectric constant properties, crystal–liquid duality, and fundamental optical processes of MHPs are first discussed. The properties of excitons and related phenomena in MHPs are then detailed, including the exciton binding energy determined by various methods and their influence factors, exciton dynamics, exciton–photon coupling and related applications, and exciton–phonon coupling in MHPs. The properties of photogenerated free charge carriers in MHPs such as the carrier diffusion length, mobility, and recombination are described. Recent progress in various applications is also demonstrated. Finally, a conclusion and perspectives of future studies for MHPs are presented.

Nonvolatile memory devices based on unipolar resistive switching in a solution‐processed organo‐metal halide perovskite are reported by Keehoon Kang, Takhee Lee, and co‐workers in article number 1804841. A facile synthesis of the perovskite layer with a nonhalide precursor allows the reliable fabrication of high‐yield cross‐bar array memory devices with a desirable ON/OFF ratio and electrical stability, which can potentially open a solution‐processing route for realizing high‐density resistive random‐access memory devices.

Low‐cost counter materials for dye‐sensitized and perovskite solar cells are summarized, with a focus on the regular patterns that appear in their intrinsic features and structural design.

Abstract

It is undoubtable that the use of solar energy will continue to increase. Solar cells that convert solar energy directly to electricity are one of the most convenient and important photoelectric conversion devices. Though silicon‐based solar cells and thin‐film solar cells have been commercialized, developing low‐cost and highly efficient solar cells to meet future needs is still a long‐term challenge. Some emerging solar‐cell types, such as dye‐sensitized and perovskite, are approaching acceptable performance levels, but their costs remain too high. To obtain a higher performance–price ratio, it is necessary to find new low‐cost counter materials to replace conventional precious metal electrodes (Pt, Au, and Ag) in these emerging solar cells. In recent years, the number of counter‐electrode materials available, and their scope for further improvement, has expanded for dye‐sensitized and perovskite solar cells. Generally regular patterns in the intrinsic features and structural design of counter materials for emerging solar cells, in particular from an electrochemical perspective and their effects on cost and efficiency, are explored. It is hoped that this recapitulative analysis will help to make clear what has been achieved and what still remains for the development of cost‐effective counter‐electrode materials in emerging solar cells.

Protonation of polyethylenimine ethoxylated (PEIE) can effectively passivate the chemical reaction between the PEIE and a nonfullerene (NF) active layer. As a result, the PEIE can work very efficiently as a low‐work‐function interface for NF solar cells. These flexible solar cells exhibit power conversion efficiency up to 12.5% with a room‐temperature‐processed PEIE interface.

Abstract

Nonfullerene (NF) organic solar cells (OSCs) have been attracting significant attention in the past several years. It is still challenging to achieve high‐performance flexible NF OSCs. NF acceptors are chemically reactive and tend to react with the low‐temperature‐processed low‐work‐function (low‐WF) interfacial layers, such as polyethylenimine ethoxylated (PEIE), which leads to the “S” shape in the current‐density characteristics of the cells. In this work, the chemical interaction between the NF active layer and the polymer interfacial layer of PEIE is deactivated by increasing its protonation. The PEIE processed from aqueous solution shows more protonated N⁺ than that processed from isopropyl alcohol solution, observed from X‐ray photoelectron spectroscopy. NF solar cells (active layer: PCE‐10:IEICO‐4F) with the protonated PEIE interfacial layer show an efficiency of 13.2%, which is higher than the reference cells with a ZnO interlayer (12.6%). More importantly, the protonated PEIE interfacial layer processed from aqueous solution does not require a further thermal annealing treatment (only processing at room temperature). The room‐temperature processing and effective WF reduction enable the demonstration of high‐performance (12.5%) flexible NF OSCs.

In article number 1807019, Ergang Wang and co‐workers review the recent progress of conjugated donor–acceptor (D–A) terpolymers for efficient polymer solar cells. Compared to D–A alternating copolymers, such terpolymers can give a facile method to not only improve their light absorption, but also fine‐tune their energy levels and interchain packing synergistically. Thereby, they highlight the great potential of terpolymers for efficient polymer solar cells.

In contrast to conjugated donaor–acceptor (D–A) alternating copolymers, incorporating a third component, either D′‐ or A′‐unit, to their D–A type polymer backbones can improve their light absorption, and tune energy levels and interchain packing synergistically. Moreover, the well‐controlled stoichiometry for these components in terpolymers also provides further access to fine‐tune these factors, thus resulting in high photovoltaic performance in polymer solar cells.

Abstract

The development of conjugated alternating donor–acceptor (D–A) copolymers with various electron‐rich and electron‐deficient units in polymer backbones has boosted the power conversion efficiency (PCE) over 17% for polymer solar cells (PSCs) over the past two decades. However, further enhancements in PCEs for PSCs are still imperative to compensate their imperfect stability for fulfilling practical applications. Meanwhile development of these alternating D–A copolymers is highly demanding in creative design and syntheses of novel D and/or A monomers. In this regard, when being possible to adopt an existing monomer unit as a third component from its libraries, either a D′ unit or an A′ moiety, to the parent D–A type polymer backbones to afford conjugated D–A terpolymers, it will give a facile and cost‐effective method to improve their light absorption and tune energy levels and also interchain packing synergistically. Moreover, the rationally controlled stoichiometry for these components in such terpolymers also provides access for further fine‐tuning these factors, thus resulting in high‐performance PSCs. Herein, based on their unique features, the recent progress of conjugated D–A terpolymers for efficient PSCs is reviewed and it is discussed how these factors influence their photovoltaic performance, for providing useful guidelines to design new terpolymers toward high‐efficiency PSCs.

Nature Photonics, Published online: 27 May 2019; doi:10.1038/s41566-019-0435-1

Nonvolatile memory devices based on unipolar resistive switching in a solution‐processed organo‐metal halide perovskite are reported by Keehoon Kang, Takhee Lee, and co‐workers in article number 1804841. A facile synthesis of the perovskite layer with a nonhalide precursor allows the reliable fabrication of high‐yield cross‐bar array memory devices with a desirable ON/OFF ratio and electrical stability, which can potentially open a solution‐processing route for realizing high‐density resistive random‐access memory devices.

Propane‐1,3‐diammonium cations are first adopted to construct cesium–formamidinium (Cs–FA) perovskite solar cells (PSCs) with an efficiency of 18.1% and much enhanced device stability, and the opposing effects induced by the diammonium cation are resolved.

Incorporating diammonium cations, which electrostatically connect the adjacent inorganic slabs ([PbI₆]⁴⁻), into 3D perovskite is recently proposed to develop high‐performance perovskite solar cells (PSCs). However, due to limited studies, the effects of these organic cations on the perovskite structural and optoelectronic properties are yet to be understood. Herein, a diammonium cation, propane‐1,3‐diammonium (PDA), is first proposed to modulate the cesium–formamidinium (Cs–FA)‐mixed cation perovskite. By increasing the PDA content, the efficiency of the Cs_0.15FA_{0.85 − x} PDA _x PbI₃ PSC first increases and then drastically decreases. The highest power conversion efficiency (PCE) of 18.10% obtained by Cs_0.15FA_0.83PDA_0.02PbI₃ is superior to that of the Cs_0.15FA_0.85PbI₃ (16.82%). Through systematic investigations, it is revealed that the PDA content–dependent efficiency is attributed to a competition between the enhanced defect passivation and emerged excitonic effect with an increased PDA content. Moreover, the encapsulated Cs_0.15FA_0.83PDA_0.02PbI₃ device exhibits almost 1.5 times increased stability than the Cs_0.15FA_0.85PbI₃ counterpart, with 83% of its initial efficiency retained after 500 h exposure, under continuous light soaking at 60 °C in ambient air. This study provides a practical strategy to enhance the device stability without sacrificing the efficiency and deepens our understanding on effects of diammonium cation incorporated in 3D perovskite.

The properties of excitons and photogenerated charge carriers in metal halide perovskites (MHPs) are explored. The properties of excitons including the exciton binding energy, exciton dynamics, and exciton–photon and exciton–phonon coupling, are discussed. The properties of photogenerated free charge carriers in MHPs such as diffusion length, mobility, and recombination are described. A brief review of recent applications is also demonstrated.

Abstract

Metal halide perovskites (MHPs) have recently attracted great attention from the scientific community due to their excellent photovoltaic performance as well as their tremendous potential for other optoelectronic applications such as light‐emitting diodes, lasers, and photodetectors. Despite the rapid progress in device applications, a solid understanding of the photophysical properties behind the device performance is highly desirable for MHPs. Here, the properties of excitons and photogenerated charge carriers in MHPs are explored. The unique dielectric constant properties, crystal–liquid duality, and fundamental optical processes of MHPs are first discussed. The properties of excitons and related phenomena in MHPs are then detailed, including the exciton binding energy determined by various methods and their influence factors, exciton dynamics, exciton–photon coupling and related applications, and exciton–phonon coupling in MHPs. The properties of photogenerated free charge carriers in MHPs such as the carrier diffusion length, mobility, and recombination are described. Recent progress in various applications is also demonstrated. Finally, a conclusion and perspectives of future studies for MHPs are presented.

The origins of defect tolerance in metal halide perovskites and the corresponding simulation results, and the impact of defects on both the performance and stability of perovskite‐based light‐emitting diodes (PeLEDs) are reviewed. In addition, an account of the defect‐passivation methods for improving the performance and stability of PeLEDs and future research directions for defect passivation are also presented.

Abstract

Metal halide perovskites (MHPs) have emerged as promising emitters because of their excellent optoelectronic properties, including high photoluminescence quantum yields (PLQYs), wide‐range color tunability, and high color purity. However, a fundamental limitation of MHPs is their low exciton binding energy, which results in a low radiative recombination rate and the dependence of PLQY on the excitation intensity. Under the operating conditions of light‐emitting diodes (LEDs), the injected current densities are typically lower than the trap density, leading to a low actual PLQY. Moreover, the defects not only initiate the decomposition of MHPs caused by extrinsic factors, but also intrinsically stimulate ion migration across the interface and lead to the corrosion of electrodes due to interaction between those electrodes, even under inert conditions. The passivation of defects has proven to be effective for mitigating the effects of defects in MHPs. Herein, the origins and theoretical calculations of the defect tolerance in MHPs and the impact of defects on both the performance and stability of perovskite LEDs are reviewed. The passivation methods and materials for MHP bulk films and nanocrystals are discussed in detail. Based on the currently reported advances, specific requirements and future research directions for display applications are suggested.

The unstable properties of hybrid perovskites, such as crystal phase transition, fragmentation of organic molecules, and hydrogen bond dissociation, are reviewed, and the importance of additives in structurally stabilizing formamidinium lead trihalide in place of methylammonium is emphasized.

Abstract

Hybrid lead halide perovskite materials are used in solar cells and show efficiencies greater than 23%. Furthermore, they are applied in light‐emitting diodes, X‐ray detectors, thin‐film transistors, thermoelectrics, and memory devices. Lead trihalide hybrid materials contain methylammonium (MA) or formamidinium (FA) (or a mixture), or long alkylammonium halides, as alternative organic cations. However, the intrinsic stability of hybrid lead halide perovskites is not very high, and they are chemically unstable when exposed to moisture, light, or heat because of their organic contents and low formation energies. Therefore, although improvements in the chemical stability are crucial, changing the material composition is challenging because it is directly related to the desired application requirements. Fortunately, hybrid lead halide perovskites have a very high tolerance toward changes in physical properties arising from doping or addition of different cations and anions, in many cases showing improved properties. Here, the intrinsic instability of hybrid lead halide perovskites is reviewed in relation to the crystal phase and chemical stability. It is suggested that FA should be used for lead halide perovskites for chemical stability instead of MA. Furthermore, additives that stabilize the crystal phase with α‐FAPbI₃ should eschew MA.

The halide composition of Pb²⁺‐based perovskite materials provides great control over their physical properties, yet the range of X ions explored in the APbX₃ perovskite motif has so far been generally confined to the series of halides Cl⁻, Br⁻, and I⁻. The possibility of polyatomic pseudohalide anions in Pb²⁺‐based perovskites is explored.

Abstract

The emerging class of lead halide perovskite (LHP) semiconductors offers a surprising combination of low cost, ease of preparation, outstanding material properties, and performance in optoelectronic devices that has not yet been observed in any other class of material. Considering their general ABX₃ formula, the halide (X) composition in LHP compositions has proven to be one of the best handles to control the material characteristics such as bandgap, morphology, and electronic properties. However, compared to the amount of effort that has been expended to discover new A cations and B cations, relatively few reports have dealt with the subject of discovering new X anions outside of the series of halides (Cl⁻, Br⁻, I⁻). In principal, a much wider range of anions with a −1 charge (pseudohalides) may form the ABX₃ stoichiometry with Pb²⁺, yet the general ability of polyatomic pseudohalides to form semiconducting perovskite crystal phases with Pb²⁺ remains an open question. Herein, the prospect of using polyatomic pseudohalide anions in LHP semiconductors is addressed.