Organometal Halide Research Articles

Laterally Grown Strain-Engineered Semitransparent Perovskite Solar Cells with 16.01% Efficiency

Hybrid organometallic halide perovskite-based semitransparent solar cell research has garnered significant attention recently due to their promising applications for smart windows, tandem devices, wearable electronics, displays, and sustainable internet-of-things. Though considerable progress has been made, stability, controlling the crystalline qualities, and growth orientation in perovskite thin films play crucial roles in improving the photovoltaic (PV) performance. Recently, strain modulation within the perovskite gathers an immense interest that is achieved by the ex situ process. However, little work is reported on in situ strain modulation, which is presented here. Apart from the challenges in the fabrication of high-efficiency perovskite solar cell (PSC) devices under ambient conditions, the stability of organic hole-transporting materials needs urgent attention. Herein, a single-step deposition of formamidiniumchloride (FACl)-mediated CH3NH3PbI3 (MAPbI3) thin films without an inert atmosphere and CuI as the inorganic hole-transporting material is demonstrated for their potential application toward semitransparent PSCs. The FACl amount in MAPbI3 (mg/mL) plays a critical role in controlling the crystallinity, growth orientations, and in situ strains, which modulate the charge carrier transport dynamics, thereby improving the efficiency of the PSC device. A photoconversion efficiency of 16.01% has been achieved from MAPbI3 with 20 mg/mL of FACl additive incorporation. The modification of the structural, electronic, and optical properties and the origin of strain in the as-synthesized MAPbI3 domains due to the addition of FACl are further validated with experimental findings in detail using density functional theory simulations.

Improving the performance of perovskite solar cells with carbon nanotubes as a hole transport layer

There are several types of organometallic halide perovskite solar cells (OHPSCs), but the carbon-based PSC has the lowest materials/fabrication cost and the longest-term stability, making it the most promising for practical application. In this study, we used multi—walled carbon nanotubes (MWCNTs) as the hole transport layer in the PSC architecture. We experimentally achieved an optimized efficiency of 13.7% for a MWCNTs-based device. Besides, this research describes a simulation-guided optimization process to fabricate high-performance MWCNT-based photovoltaics. We have thoroughly investigated the effect of different parameters, such as the total defect density of the absorber, the thickness of the MWCNTs film, the thickness of the absorber, shunt resistance, series resistance, and temperature, utilizing numerical simulations. By using the thin film photovoltaic program SCAPS-1D, we were able to simulate defect states and interfaces between layers to get as close as possible to a realistic PSC in our simulations and analysis. An optimized PSC of F-doped tin oxide (FTO)/titanium dioxide (TiO2)/MAPbI3/MWCNTs/gold (Au) is designed here with a voltage-open circuit (VOC) of 1.100 V, a short-current density (JSC) of 19.192 mA/cm2, and efficiency of 18.3% with a high fill factor (FF) of 86.62%, which is among the best for carbon-based OHPSCs.

UV-Blocking and Transparent Polydimethylsiloxane Film for Improving Stability of Perovskite Photovoltaics

Long-term stability of high-power conversion efficiency (PCE) against UV degradation is imperative to commercialize organometallic halide perovskite solar cells (PSCs). This degradation problem can be solved by blocking UV light, but it leads to a decrease in the PCE due to the decrease in the total amount of absorbed light in the PSC devices. Here, we propose a facile strategy for this challenging problem by attaching textured and UV-blocking bilayer PDMS films with a gradient refractive index onto the glass of PSC devices. We fabricated a gradient-refractive-indexed PDMS film by adopting a two-layer structure─a pure PDMS layer and a UV blocker (2,2′-dihydroxy-4-methoxy benzophenone)-added PDMS layer. The two-layer structure of PDMS films blocked the UV region (>380 nm) and increased the average transmittance by 1.8% at 600–800 nm due to the gradient refractive index. Additionally, the two-layered PDMS films were surface-textured by pattern replication from chemically etched Si surfaces. Surface texturing improved the average transmittance by 4.11% in the visible region as compared to that for the pure-flat PDMS film. The final PDMS film exhibited blocking of light >380 nm and enhanced absorption in the 400–800 nm region. As a result, MAPbI3 PSCs with a surface-textured bilayer PDMS film showed 0.8% higher PCE than did pristine devices. The PCE of the encapsulated device maintained over 90% of its initial performance after 240 h at 55% relative humidity under outdoor conditions and delivered 87% device performance even with additional UV irradiation after 240 h.

Development for Highly Efficient Organometal Halide Perovskite Solar Cells and Modules

Organometal halide perovskites have captured wide interest as a promising material for light-weight and high-efficiency solar cells. Through recent studies of the organometal halide perovskite solar cells (PSCs), the composition of organometal halide perovskites is recognized as one of the key factors in the improvement of the PCE. In this study, we investigated mixed cation perovskite absorber. Additionally, we successfully constructed monolithic PSC mini-module without I-V hysteresis. In the case of MA-free PSCs, the 24.9% PCE (0.187 cm2) and 21.6% PCE (2.76 cm2 monolithic PSC mini-module) were obtained, respectively. We also developed semitransparent perovskite top cells with higher durability and transmittance for tandem solar cells. The PCEs of 19.5% (certified 19.3%) and 26.2% were achieved for a 1 cm2 semi-transparent perovskite top cell and four-terminal PSC/CIGS tandem solar cells, respectively.

Ultrahigh Photoluminescence Quantum Yield Organic Manganese Halide Scintillator for X-ray Imaging

X-ray indirect detection based on metal halide scintillators has great potential in various applications, such as medical diagnosis, computerized tomography, and quality inspection. However, there are still many limitations in metal halide scintillation materials, such as toxicity, high production costs, and strong self-absorption caused by a band-edge transition limiting the photoluminescence quantum yield (PLQY). Here, (TEA)2MnCl4 and (TBA)2MnCl4 single crystals as scintillators with advanced properties were synthesized from TEAC (tetraethylammonium chloride), TBAC (tetrabutylammonium chloride), and manganese chloride by an antisolvent method at room temperature. These two zero-dimensional organometallic halides exhibit green emission peaking at 512 nm ((TBA)2MnCl4) and 524 nm ((TEA)2MnCl4) with high PLQYs of 99.96% and 65.07%, respectively. The ultrahigh PLQY of (TBA)2MnCl4 benefits from the long Mn–Mn distance in (TBA)2MnCl4. (TBA)2MnCl4 shows an outstanding scintillation performance with a high light yield of 21000 photons/MeV, a low detection limit of 381 nGy/s, and a spatial resolution of 5.6 lp/mm. X-ray imaging experiments demonstrate that the flexible scintillators based on (TEA)2MnCl4 and (TBA)2MnCl4 could be used in high-resolution X-ray imaging.

Photoinduced Strain in Organometal Halide Perovskites.

There is a lack of fundamental understanding of mechano-electro-optical multifield coupling for organometallic halide perovskites (OHPs). In this study, the effect of light irradiation on OHPs' mechanical properties was investigated by atomic force microscopy. In the dark, an MAPbI3 film was dominated by grains with a Young's modulus of approximately 5.94 GPa, which decreased to 2.97 GPa under light illumination. The photoinduced strain distribution within the polycrystalline MAPbI3 film was not uniform, and the maximum strain generated inside individual grains was 5.8%. Furthermore, the illumination-induced strain promoted the formation of ferroelastic domains. The Young's modulus of one domain increased from 8.99 to 25.27 GPa, whereas the Young's modulus of an adjacent domain decreased from 14.9 to 1.30 GPa. According to the density-functional-theory calculations, the observed photoinduced strain-promoted variations in mechanical properties were caused by the reversible migration of MA+ cations. These findings can help establish the relationship among the mechanical-chemical-optoelectronic characteristics of OHPs.

Improving the Performance and High-Field Stability of FAPbBr3 Single Crystals in X-Ray Detection with Chenodeoxycholic Acid Additive.

Organometal halide perovskite single crystals are one of the most promising radiation detection materials due to their unique advantages of high absorption coefficient, long carrier diffusion length, and low defect density. However, the severe ion migration in perovskites deteriorates the X-ray detection performance under longtime and high-field operating conditions. This work reports an effective additive of chenodeoxycholic acid (CDCA), which can suppress the ion migration and improve the performance and the operational stability of FAPbBr3 single crystals (SCs) in X-ray detection significantl. The CDCA molecules in precursors effectively suppress the decomposition of FA ions, resulting in a better crystal orientation and stoichiometry. The trace amounts of CDCA residues in FAPbBr3 SCs improve the thermal stability and effectively suppress the ion migration. The resulting detector shows an impressive X-ray sensitivity up to 21386.88 µC Gyair -1 cm-2 under -500V and a detection limit of 15.23 nGyair s-1 . The response current of the detector at 225V cm-1 field is barely changed under the 7200 s irradiation with a dose rate of 1.949 mGyair s-1 . This work provides insights for the additive selection and improving the operational stability of perovskite single crystals for commercial applications.

Organolead Halide-Based Coordination Polymers: Intrinsic Stability and Photophysical Applications

ConspectusOrganolead halide-based photovoltaics are one of the state-of-the-art solar cell systems with efficiencies increasing to 25% over the past decade, ascribed to their high light-absorption coefficient, broad wavelength coverage, tunable band structure, and excellent carrier mobility. Indeed, these optical characteristics are highly demanding in photocatalysis and photoluminescence (PL), which also involve the solar energy utilization and charge transport. However, the vast majority of organolead halides are ionically bonded structures and susceptible to degradation upon high-polarity protic molecules (e.g., water (vapor) and alcohol), which are often inevitable in many photochemical applications. Encapsulation is a commonly used stabilization approach by coating protective layers, avoiding the direct contact between organolead halides and polar molecules. However, this may partially hinder the light penetration to the inner hybrid halide materials, and introduce new interface problems that are important in photocatalysis and luminescent sensing. Therefore, developing intrinsically stable organometal halide hybrids is a major target for their applications in optoelectronic applications.In this Account, recent research progress on the synthesis of organolead halide-based coordination polymers for a variety of photoactive applications is described. Herein, we propose a general strategy to advance the intrinsic stability of organometal halide crystalline materials by using coordinating anionic organic linkers, which occupy the excellent photophysical features analogous to those of perovskites. Unlike the organoammonium cations as for ionically bonded structures, the anionic structure-directing agents (e.g., organocarboxylates) render well-defined metal-carboxylate coordination motifs in extended architectures spanning from low-dimensional (0D, 1D) to high-dimensional cationic inorganic Pb-X-Pb (X = F-/Cl-/Br-/I-) sublattices. This family of organolead halide coordination polymers can endure chemically reactive environments over a wide range of pH and aqueous boiling condition, which have been systematically investigated by experimental studies and theoretical calculations. Many chloride/bromide-based coordination polymers show air-stable, broadband self-trapped emission with large Stokes shift and high color rendition, exhibiting the absolute quantum yields of 35-72%. Among them, the porous frameworks with low-dimensional (0D, 1D) inorganic blocks are recognized as a rare class of porous metal-organic frameworks (MOFs) constructed by lead halides as secondary building units (SBUs). They not only occupy substantially higher light-harvesting and carrier-transport properties than conventional metal oxide-based MOFs, but also allow for isoreticular modification to regulate the PL characteristics by guest molecules. More importantly, combining the high stability with excellent carrier characteristics, a layered organolead iodide coordination polymer shows the overall photocatalytic water splitting without the use of any sacrificial agent under simulated sunlight illumination. Given the wide choice of structurally diverse organocarboxylate linkers, we hope this Account provides deep insights on the importance of coordination chemistry in the discovery of a wide family of intrinsically stable organolead halides to expand their photophysical applications.

Improvement of a Two-step Method for Highly Efficient Perovskite Solar Cells via Modification of a Metal Halide Template and Dipping Conditions

We report an improved two-step method for the development of highly efficient organometal halide perovskite solar cells (PSCs). The improvement of the two-step method has been achieved with the modification of the metal halide template and the controlling of the dipping solution temperature. With a single cation methylammonium lead iodide PSC fabricated via a modified PbI2 template and the dipping solution temperature of 70 °C, we have accomplished a PCE of 17.14% enhanced from the conventional two-step methods.

Challenges and Potential of Perovskite Solar Cells

A solar cell is a device that converts sunlight into electricity. There are different types of solar cells but in this literature mainly focuses on a type of new dominant solar cell material that has the name organo-metal halide perovskite, namely known as perovskite solar cells, in shortly PSCs . In this respect, the efficiency of power conversion is taken into account to replace the dominancy of traditional and second generation solar cell fields by perovskite solar cells. Perovskite solar cell is a type of solar cell including a perovskite structure, usually a hybrid organic-inorganic lead or tin halide- based material. In this review, a comprehensive study of the perspective challenges and their potential has been highlighted for their future application. There are rigorous research efforts in aspects of device engineering, including physical and chemical passivation, and the use of a wide variety of organic and inorganic additives to develop the advanced PSCs.

Zero-dimensional Cu(I)-based organometallic halide with green cluster-centred emission for high resolution X-ray imaging screens.

In this communication, we report a low-dimensional perovskite-related structure based on Cu(I) organometallic halide with strong green cluster-centred emission and near-unity photoluminescence quantum yield. The 0D [Rb(18-crown-6)]2Cu4I6 was sucessfully applied for X-ray imaging screens which exhibit high spatial resolution of 16.8 lp mm-1 and low detection limit of 458 nGy s-1.

Study the effect of total defect density variation in absorbing layer on the power conversion efficiency of lead halide perovskite solar cell using SCAPS-1D simulation tool

Perovskite solar cells (PSCs) are known as 3rd generation solar cells that have enormous potential to be commercialised. But the major drawback is less stability and degraded performance with the passage of time. Various parameters that contribute to their efficiency are doping concentration of charge carriers, thickness of absorbing layer and total defect density. This paper presents a numerical study on inverted planar organometal lead halide perovskite based solar cells using NiO as hole transport layer (HTL) and SnO2 as electron transport layer (ETL). The structure ITO/NiO/CH3NH3PbI3/SnO2/metal contact is simulated using SCAPS-1D software. Here we investigate the effect of variation of total defect density on the efficiency of perovskite solar cell at the layer thickness of 320 nm. The simulated device reported a Power conversion efficiency (PCE) of 25.5% at the total defect density level of 1015 cm−3, VOC of 1.06 V and Fill Factor (FF) of 0.80. Further analysis revealed a declining trend in the (PCE) value from 25.5% to 1.85% on increasing the defect density from 1015 to 1018 cm−3. This trend is detrimental for the overall performance of the device.

Highly flexible organo-metal halide perovskite solar cells based on silver nanowire-polymer hybrid electrodes.

Flexible perovskite solar cells (FPSCs) have attracted considerable attention due to their broad application possibilities in next generation electronics. However, the commonly used transparent conductive electrodes (TCEs), such as indium tin oxide (ITO), suffer from poor flexible performance, impeding the development of FPSCs. Here, we propose a hybrid electrode (PUA/AgNWs/PH1000) comprising a thin percolation network of silver nanowires (AgNWs) inlaid on the surface of a flexible substrate (PUA) modified with a conductive layer (PH1000), which exhibits high optical transmittance and electrical conductivity, as well as robust mechanical flexibility. By applying the proposed PUA/AgNWs/PH1000 hybrid electrode in FPSCs, the resulting ITO-free devices exhibit the desired flexibility and mechanical stability; it can survive repeated continuous bending cycles and retain 77.4% of its initial power conversion efficiency after 10 000 bending cycles with the bending radius of 5 mm.

Correction: An organometal halide perovskite photocathode integrated with a MoS2 catalyst for efficient and stable photoelectrochemical water splitting

Correction for ‘An organometal halide perovskite photocathode integrated with a MoS2 catalyst for efficient and stable photoelectrochemical water splitting’ by Hojoong Choi et al., J. Mater. Chem. A, 2021, 9, 22291–22300, https://doi.org/10.1039/D1TA05377A.

Controlling Threshold and Resistive Switch Functionalities in Ag‐Incorporated Organometallic Halide Perovskites for Memristive Crossbar Array

AbstractHalide perovskites (HPs) can be the effective functional materials for the sneak‐path current issue in the memristive crossbar array. Herein, an efficient strategy is proposed to integrate the HPs‐based bidirectional threshold and bipolar resistive switches (TS and RS). The resistance change characteristics from volatile threshold to nonvolatile resistive switching are modulated by controlling Ag doping concentration in the MAPbI3. HPs provide the diffusive condition and the quantity of Ag regulates the radius of its network. A low amount of Ag contributes to weak network with a short lifetime. However, when the amount of Ag increases, the conductive filament becomes more robust, showing a long lifetime. A MAPbI3:Ag TS with a low Ag content is developed, showing a steep switching slope (1 mV per decade), fast switching speed (< 80 ns), and low off‐current (10 nA). And, a MAPbI3:Ag RS with a high Ag content is developed, showing multilevel storage capability and long retention time (1400 s). Finally, these TS and RS coupled into the 1S‐1R integrated component, resulting the development of the maximum crossbar array size to 1.4 × 1012. This study offers an efficient methodology for tailoring the resistance change characteristics and a promising strategy for practical HPs‐based memristive crossbar application.

Tailoring the PEDOT:PSS hole transport layer by electrodeposition method to improve perovskite solar cells

Organometallic halide perovskites have emerged in the last decade as promising light absorbers for solar cell development. These devices require functional layers for both generated hole and electron extraction and transport. Among the hole transporting materials (HTM), poly(3,4-ethylenedioxythiophene) poly-(styrenesulfonate) or PEDOT:PSS layers have been widely obtained from a colloidal suspension. As an alternative, PEDOT:PSS can also be electrochemically deposited, allowing for synthesis control and performance design. In this study, the effect of the electrodeposition method of PEDOT on its HTM properties and solar cell efficiency was evaluated. The result showed a decrease in the HTM charge carrier density with the increase in the polymerization potential. When this potential is around 1.5 V (vs Ag/AgCl), the Raman spectra suggest the formation of side groups in the polymer chains resulting from over-oxidation. HTMs with a high charge carrier density increased the short-circuit current density (Jsc) and fill factor (FF) but reduced the open-circuit potential (Voc) of the solar cells. To avoid overoxidation, low synthesis potentials were applied. With this strategy, a 15.0% power conversion efficiency (PCE) was achieved using the galvanostatic method at 0.1 mA cm−2, where the applied potential was ∼1 V. Consequently, this work paves the way for the optimization of the solar cell by simply controlling the electrodeposition potential of the PEDOT as HTM.

Ultrafast laser spectroscopy uncovers mechanisms of light energy conversion in photosynthesis and sustainable energy materials

The invention of the laser in 1960 gave us the ruby laser, which generally produced chaotic pulses of light. Six years later, in 1966, a concept called passive mode-locking applied to neodymium-glass lasers produced reasonably well-behaving picosecond pulses. This triggered an intense activity, with respect to developing improved laser pulse sources, measurement techniques, and application to chemistry, physics, and biology. Initially, only ∼10 –ps-long pulses at a few wavelengths were available. Nevertheless, insight into the function of complex biological systems, like photosynthetic proteins, and molecules of chemical interest was gained in very early studies. Today, both duration and color of ultrashort pulses can be tuned to almost any value. This has of course opened up possibilities to study almost any atomic, molecular, or solid-state system and any dynamic process. This review focuses on the use of laser spectroscopy to investigate light energy conversion mechanisms in both natural photosynthesis and a topical selection of novel materials for solar energy conversion. More specifically, in photosynthesis we will review light harvesting and primary electron transfer; materials for solar energy conversion that we discuss include sensitized semiconductors (dye sensitized solar cells), polymer:fullerene and polymer:polymer bulk heterojunctions (organic solar cells), organometal halide perovskites, as well as molecular and hybrid systems for production of solar fuel and valuable chemicals. All these scientific areas, and in particular photosynthesis and the solar cell materials, have been extensively studied with ultrafast spectroscopy, resulting in a vast literature; a comprehensive review of the individual materials is, therefore, not feasible, and we will limit our discussion to work that we think has been of particular importance for understanding the function of the respective systems.

Moisture-Dependent Blinking of Individual CsPbBr3 Nanocrystals Revealed by Single-Particle Spectroscopy.

All-inorganic metal halide perovskite nanocrystals (NCs) have been exceptional candidates for high-performance solution-processed optoelectronic and photonic devices compared with organometal halide perovskite NCs due to their superior stability. However, the interactions between all-inorganic perovskite NCs and moisture, which is an acknowledged detrimental factor, are still under debate, and detailed investigations to uncover such fundamentals remain to be performed. Herein, with wide-field fluorescence microscopy, the burst photoluminescence blinking responses of CsPbBr3 NCs were observed in ambient air, and moisture rather than oxygen was verified to be the key factor that leads to the enhanced PL intensity and reduced OFF duration. This behavior is rationalized through an effective passivation effect of the adsorbed water molecules on the surface halide vacancies on CsPbBr3 NCs. This work validates that ∼40% humidity atmospheres are helpful for better utilizing the all-inorganic perovskites, which is evidence of their promising prospect for application.

Control of perovskite film crystallization and growth direction to target homogeneous monolithic structures

Getting performant organo-metal halide perovskite films for various application remains challenging. Here, we show the behavior of solvent and perovskite elements for four different perovskites families and nine different initial precursor solution systems in the case of the most popular preparation process which includes an anti-solvent dripping-assisted spin coating of a precursor solution and a subsequent thermal annealing. We show how the initial solution composition affects, first, the film formed by spin coating and anti-solvent dripping and, second, the processes occurring upon thermal annealing, including crystal domain evolution and the grain growth mechanism. We propose a universal typology which distinguishes three types for the growth direction of perovskite crystals: downward (Type I), upward (Type II) and lateral (Type III). The latter results in large, monolithic grains and we show that this mode must be targeted for the preparation of efficient perovskite light absorber thin films of solar cells.

Optimization of tin based perovskite solar cell employing CuSbS2 as HTL: A numerical simulation approach

The expeditious progresses in the domain of organo-metallic halide perovskite solar cells has resulted in PCE of more than 25.5%. However, their extensive utilization and fully fledged commercialization is currently restricted owing to the existence of expensive hole transport layer (HTL) viz Spiro-OmeTAD in the novel devices. In this paper, a low cost and easily available materials i.e. CuSbS2 and fullerene (C60) are endeavored as HTL and ETL respectively, by utilizing SCAPS 1D simulator, which can also yield high solar cell performance. In this context, the analysis of Spiro-OmeTAD, CuSbS2 as HTLs and TiO2, C60 as ETLs has been validated. In addition, effect of thickness of HTLs on perovskite solar cells using CH3NH3SnI3 as light harvester & C60 as hole inhibiting layer/electron transport layer (ETL) has been also examined. The recommended simulation reveals that using 20 nm of CuSbS2 layer can outperform Spiro-OmeTAD as HTL for cell fabrication. It has been observed that by employing proposed perovskite solar cell configuration FTO/C60/CH3NH3SnI3/CuSbS2/Au, an efficiency (PCE) of 26.05% associated with fill factor (FF) of 82.98%, short circuit current (Jsc) of 31.646 mA/cm2 & open circuit voltage (Voc) of 0.9918 V can be yielded which assures exhibition of better solar cell performance than the existing solar cell.