Lead Halide Perovskite Solar Cells Research Articles

Thermal Stability Analysis of Formamidinium–Cesium‐Based Lead Halide Perovskite Solar Cells Fabricated under Air Ambient Conditions

The instability of perovskite solar cells (PSCs) remains a major bottleneck for their commercialization, with thermal instability posing a major concern, given the inevitable presence of heat in photovoltaic devices. Mixed‐cation/halide perovskites demonstrate enhanced stability and efficiency compared to single‐cation/halide perovskites. Identifying the optimal perovskite composition capable of withstanding high temperatures for longer durations is crucial for the development of thermally stable PSCs. This study provides valuable insights into the optimization of mixed‐cation/halide perovskites to enhance the thermal and structural stability of perovskite films. By systematically varying the Cs content in FA1−yCsyPb(I0.85Br0.15)3 (0 < y < 25)‐based perovskite, it is observed that controlling the Cs content allows precise modulation of crystal orientation in perovskite film with 10% Cs obtained as the optimal value. The perovskite film containing 10% Cs not only exhibits reduced microstrain but also demonstrates enhanced thermal stability during testing at 85 °C under controlled humidity. Furthermore, planar PSCs are fabricated using FA0.90Cs0.10Pb(I0.85Br0.15)3 as the absorber layer and TOP‐3 as the hole‐transporting material, achieving a promising power conversion efficiency (PCE) of 17.70%. Impressively, the unencapsulated devices retain 95% of their initial PCE after 1000 h of dark storage under ambient conditions.

Impact of La doping on the optoelectronic and structural properties of CsPbIBr2 perovskite solar cell

Inorganic lead halide perovskite solar cells (IPSC) have high power conversion efficiency (PCE). Currently, heteroatom substitution is a promising method for enhancing the properties of perovskite materials and the performance of associated devices. This study outlines the production process of a perovskite solar cell made from inorganic CsPbIBr2 with a 4 % La doping. The cubic crystal structure with large grain size and small band gap energy is observed at 4 % La–CsPbIBr2. The optoelectronic and structural characteristics of CsPbIBr2 perovskite solar cells have been substantiated through various methodologies, such as the determination of space charge restricted current, examination of the photoluminescence decay profile, assessment of charge transfer resistance, and utilization of Mott Schottky analysis. The incorporation of lanthanum-doped cesium lead iodide bromide (La-doped CsPbIBr2) resulted in a notable enhancement in both the open circuit voltage (Voc), and the short circuit current density (Jsc), leading to a much higher overall efficiency of 9.89 % compared to the pristine counterpart, which exhibited an efficiency of 8.62 %.

Simultaneous Li-Doping and Formation of SnO2-Based Composites with TiO2: Applications for Perovskite Solar Cells.

Tin oxide (SnO2) has been recognized as one of the beneficial components in the electron transport layer (ETL) of lead-halide perovskite solar cells (PSCs) due to its high electron mobility. The SnO2-based thin film serves for electron extraction and transport in the device, induced by light absorption at the perovskite layer. The focus of this paper is on the heat treatment of a nanoaggregate layer of single-nanometer-scale SnO2 particles in combination with another metal-dopant precursor to develop a new process for ETL in PSCs. The combined precursor solution of Li chloride and titanium(IV) isopropoxide (TTIP) was deposited onto the SnO2 layer. We varied the heat treatment conditions of the spin-coated films comprising double layers, i.e., an Li/TTIP precursor layer and SnO2 nanoparticle layer, to understand the effects of nanoparticle interconnection via sintering and the mixing ratio of the Li-dopant on the photovoltaic performance. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the sintered nanoparticles suggested that an Li-doped solid solution of SnO2 with a small amount of TiO2 nanoparticles formed via heating. Interestingly, the bandgap of the Li-doped ETL samples was estimated to be 3.45 eV, indicating a narrower bandgap as compared to that of pure SnO2. This observation also supported the formation of an SnO2/TiO2 solid solution in the ETL. The utilization of such a nanoparticulate SnO2 film in combination with an Li/TTIP precursor could offer a new approach as an alternative to conventional SnO2 electron transport layers for optimizing the performance of lead-halide perovskite solar cells.

Methylammonium Nitrate-Mediated Crystal Growth and Defect Passivation in Lead Halide Perovskite Solar Cells

Methylammonium Nitrate-Mediated Crystal Growth and Defect Passivation in Lead Halide Perovskite Solar Cells

Exploring various Integration Methods of carbon quantum dots in CsPbCl3 perovskite solar cells for enhanced power conversion efficiency

In this study, we explore the integration of carbon quantum dots (QDs) in cesium lead halide perovskite solar cells (PSCs) across the electron transport layer (ETL), hole transport layer (HTL), and the perovskite absorber to enhance power conversion efficiency (PCE). We conduct a comprehensive investigation from thin film analysis to complete device characterization, encompassing eight different device topologies. Our results reveal that the integration of QDs in various layers significantly impacts the performance of the PSCs. Notably, adding QDs in the HTL and ETL improves charge transport and reduces recombination, enhancing device efficiency. Furthermore, introducing QDs in the perovskite layer leads to modifications in the energy landscape, reducing charge trapping and enhancing stability. We observe a trade-off between short-circuit current and overall PCE, with different QD integration strategies yielding distinct performance outcomes. Additionally, incorporating QDs in the ETL layer reduces hysteresis, attributed to mitigated ion migration and charge-trapping effects. Overall, the addition of QDs in these layers demonstrates improved charge transport, reduced recombination, and enhanced stability, ultimately contributing to the enhanced performance and efficiency of perovskite solar cells, reaching 22.5%. This study paves the way for future investigations into the potential of QDs in PSC technology and their impact on device forecasting and operational stability.

Encapsulating perovskite solar cells for long-term stability and prevention of lead toxicity

Lead halide perovskite solar cells (PSCs) have achieved remarkable efficiencies comparable to those of their established silicon counterparts at a very fast pace. Moreover, solution-processable facile technologies offer low-cost, low-temperature, scalable fabrication of these solar cells. Numerous studies have focused on improving the performance, stability, and processing of PSCs. However, potential lead toxicity and poor long-term stability impede their commercialization. In recent years, several studies have developed novel encapsulants for PSCs that can simultaneously improve stability and impede potential lead leakage. Although improvements have been made on both fronts, no solution to date could achieve a level of stability and leakage prevention that could result in a market breakthrough. Here, we analyze PSC encapsulation and lead leakage prevention techniques undertaken in recent years. While most of the related studies focused on improving either stability or toxicity, we note that both can be solved together with a suitable encapsulant that is impermeable to both moisture and Pb2+ ions. In addition, the lack of a unified standard stability testing protocol has led to stability testing under a variety of temperatures, humidities, and environmental conditions. Therefore, the urgency for a standard protocol for stability and lead toxicity testing cannot be overlooked.

Hybrid Organic-Inorganic ZnO/PCBM Electron Transport Layer with Organic Lead Halide Perovskite Solar Cell Materials CH3NH3PbIX2, X is Cl or I

An experimental investigation has been undertaken to explore a variety of properties of organic perovskite solar cells (OPSCs) that are distinct in their photovoltaic response. In this study, OPSCs were constructed using zinc oxide, ZnO and [6,6]-phenylC[Formula: see text]-acid methyl ester, PCBM, as electron transfer materials (ETM), poly(3-hexylthiophene), P3HT, as hole transport material (HTM), and CH3NH3PbIX2 as a photosensitizer, where X is either Cl or I. The structural and optical characteristics of the ETM and HTM layers and the perovskite materials of OPSCs were investigated. The [Formula: see text]–[Formula: see text] and [Formula: see text]–[Formula: see text] curves of each solar cell prepared in OPSCs were measured using an integrated cell tester. This comprises a photovoltaic [Formula: see text]–[Formula: see text] measurement system and a solar simulation system. As a result of these results, the OPSC’s performance is evaluated. The calculations in this work suggest that the highest power conversion efficiency (PCE = 6.31%) was achieved in photovoltaic devices using CH3NH3PbI3 as the effective absorber layer and ZnO with PCBM as the ETM layer. At a light intensity of 100 mW/cm2, each OPSC cell was performed. Under the same conditions, the [Formula: see text]–[Formula: see text] curves were evaluated for each OPSC device. By improving the selection of organic and inorganic active materials in the ETM layer, OPSC performance may be improved.

Limitations and Progresses in Carbon-Based Cesium Lead Halide Perovskite Solar Cells.

Inorganic cesium lead halide perovskites (CsPbIx Br3-x , 0≤x≤3) are promising alternatives with great thermal stability. Additionally, the choice of moisture-resistive and dopant-free carbon as the electrode material can simultaneously solve the problems of stability and cost. Therefore, carbon electrode-based inorganic PSCs (C-IPSCs) represent a promising candidate for commercialization, yet both the efficiencies and stability of related devices demand further progress. This article reviews the recent advancement of C-IPSCs and then unravels the distinctive merits and limitations in this field. Subsequently, our perspective on various modification strategies is analyzed on a methodological level. Finally, this article outlooks the promising research contents and the remaining unresolved issues in this field. We believe that understanding and analyzing the related problems in this field are instructive to stimulate the future development of C-IPSCs.

Recent Advancements in Enhancing Interfacial Charge Transport for Perovskite Solar Cells

Finding the most suitable pathways to improve the interfacial charge transportation in lead halide perovskite solar cells is a highly desirable research area to enhance device performance and enable commercialization. The complexities of interfacial charge dynamics, encompassing separation, diffusion, and collection processes, pivot on the thoughtful selection of interlayers and their inherent properties. Challenges arise from nonideal interfaces characterized by mismatched energy levels and defects that hinder efficient charge transport. To address these concerns, implementing tailored interfacial engineering strategies, including interlayer modification, band alignments, and passivation techniques, can help mitigate unwanted nonradiative recombination. This review aims to elucidate the impact of trap states on suppressing charge transport in the device, along with subsequent passivation techniques designed to enhance interfacial charge transport. Following that, a comprehensive overview is presented, highlighting recent advancements in interface engineering techniques that improve interfacial properties between the electron transport layer/perovskite and perovskite/hole transport layer. Significantly, the impact of using buffer and dipole layers as interlayers on overall device performance and stability is investigated.

Progress and applications of (Cu–)Ag–Bi–I semiconductors, and their derivatives, as next-generation lead-free materials for photovoltaics, detectors and memristors

The search for efficient but inexpensive photovoltaics over the past decade has been disrupted by the advent of lead-halide perovskite solar cells. Despite impressive rises in performance, the toxicity and stability concerns of these materials have prompted a broad, interdisciplinary community across the world to search for lead-free and stable alternatives. A set of such materials that have recently gained attention are semiconductors in the CuI–AgI–BiI3 phase space and their derivatives. These materials include ternary silver bismuth iodide compounds (Ag aBi bI a+3 b), ternary copper bismuth iodide Cu–Bi–I compounds and quaternary Cu–Ag–Bi–I materials, as well as analogues with Sb substituted into the Bi site and Br into the I site. These compounds are comprised of a cubic close-packed sub-lattice of I, with Ag and Bi occupying octahedral holes, while Cu occupies tetrahedral holes. The octahedral motifs adopted by these compounds are either spinel, CdCl2-type, or NaVO2-type. NaVO2-type Ag aBi bI a+3 b compounds are also known as rudorffites. Many of these compounds have thus far demonstrated improved stability and reduced toxicity compared to halide perovskites, along with stable bandgaps in the 1.6–1.9 eV range, making them highly promising for energy harvesting and detection applications. This review begins by discussing the progress in the development of these semiconductors over the past few years, focusing on their optoelectronic properties and process–property–structure relationships. Next, we discuss the progress in developing Ag–Bi–I and Cu–Bi–I compounds for solar cells, indoor photovoltaics, photodetectors, radiation detectors and memristors. We conclude with a discussion of the critical fundamental questions that need to be addressed to push this area forward, and how the learnings from the wider metal-halide semiconductor field can inform future directions.

Passivating A-Site and X-Site Vacancies Simultaneously via N-Heterocyclic Amines for Efficient Cs2AgBiBr6 Solar Cells.

To address the toxicity and stability issues of traditional lead halide perovskite solar cells (PSCs), the development of lead-free PSCs, such as Cs2AgBiBr6 solar cells, is of great significance. However, due to the low defect formation energy of Cs2AgBiBr6, a large number of vacancies, including A-site vacancies and X-site vacancies, form during the fabrication process of the Cs2AgBiBr6 film, which seriously damage the performance of the devices. The traditional phenylethylammonium (PEA) cation, mainly focusing on passivating A-site vacancies, is incapable of reducing X-site vacancies and so results in a limited performance improvement in Cs2AgBiBr6 solar cells. Herein, inspired by the capability of the Lewis base to coordinate with metal cations, a series of N-heterocyclic amines are introduced to serve as a dual-site passivator, reducing A-site and X-site vacancies at the same time. The highest power conversion efficiency of modified Cs2AgBiBr6 solar cells has been increased 36% from 1.10 to 1.50%. Further investigation reveals that the higher electron density of additives would lead to a stronger interaction with metal cations like Ag+ and Bi3+, thus reducing more X-site defects and improving carrier dynamics. Our work provides a strategy for passivating perovskite with various kinds of defects and reveals the connection between the coordination capability of additives and device performance enhancement, which could be instructive in improving the performance of lead-free PSCs.

Recent Developments in Atomic Layer Deposition of Functional Overlayers in Perovskite Solar Cells.

Over the last decade, research in organic-inorganic lead halide perovskite solar cells (PSCs) has gathered unprecedented momentum, putting the technology on the brink of full-scale commercialization. A wide range of strategies have been implemented for enhancing the power conversion efficiency of devices and modules, as well as improving stability toward high levels of irradiation, temperature, and humidity. Another key element in the path to commercialization is the scalability of device manufacturing, which requires large-scale deposition of conformal layers without compromising the delicate structure of the perovskite film. In this context, atomic layer deposition (ALD) tools excel in depositing high-quality conformal films with precise control of film composition and thickness over large areas at relatively low processing temperatures. In this commentary, we will briefly outline recent progress in PSC technology enabled by ALD tools, focusing on layers deposited above the absorber layer. These interlayers include charge transport layers, passivation layers, buffer layers, and encapsulation techniques. Additionally, we will discuss some of the challenges and potential avenues for research in PSC technology underpinned by ALD tools.

Fabrication of ambient processed carbon-based inorganic silver bismuth iodide solar cells without any expensive hole transport materials

Recently, tremendous progress has been made in inorganic–organic hybrid lead halide perovskite solar cells (PSCs). Still, most of the reported high-efficiency PSCs were made with harmful lead (Pb), which is one of the major obstacles to large-scale adoption. Silver bismuth iodide (AgBiI4) light absorbers have been identified as promising lead-free and low-toxic metal-halide materials for solar cell applications. Here, we present hole transport material (HTM) and lead-free carbon-based inorganic Rudorffite (AgBiI4) solar cells, which can be prepared by simple spin-coating using silver iodide and bismuth iodide precursors under ambient conditions. Powder X-ray diffraction (XRD), UV–visible absorption, and field emission scanning electron microscopy (FESEM) studies were used to characterize the deposited films. The performance of the fabricated device was studied using incident photon-to-current conversion efficiency (IPCE) and current density–voltage (J-V) characteristics. Electrochemical impedance spectroscopy (EIS) was used to investigate the charge transfer process at the interface of the fabricated device. Under standard illumination test conditions, the fabricated device showed a photoelectric conversion efficiency (PCE) of 1.04%. The devices also have good stability and retained 96% of their initial PCE after 200 hrs of storage in ambient conditions. This work demonstrates the potential of HTM-free, ambient processable, and lead-free Rudorffite stable solar cells.

Exploration of Solution-Processed Bi/Sb Solar Cells by Automated Robotic Experiments Equipped with Microwave Conductivity.

Solution-processed inorganic solar cells with less toxic and earth-abundant elements are emerging as viable alternatives to high-performance lead-halide perovskite solar cells. However, the wide range of elements and process parameters impede the rapid exploration of vast chemical spaces. Here, we developed an automated robot-embedded measurement system that performs photoabsorption spectroscopy, optical microscopy, and white-light flash time-resolved microwave conductivity (TRMC). We tested 576 films of quaternary element-blended wide-bandgap Cs-Bi-Sb-I semiconductors with various compositions, organic salt additives (MACl, FACl, MAI, and FAI, where MA and FA represent methylammonium and formamidinium, respectively), and thermal annealing temperatures. Among them, we found that the maximum power conversion efficiency (PCE) was 2.36%, which is significantly higher than the PCE of 0.68% for a reference film without an additive. Machine learning (ML) and statistical analyses revealed significant features and their relationships with TRMC transients, thereby demonstrating the advantages of combining ML and automated experiments for the high-throughput exploration of photovoltaic materials.

Humidity-Induced Degradation Processes of Halide Perovskites Unveiled by Correlative Analytical Electron Microscopy.

Improving the stability of lead halide perovskite solar cells (PSCs) for industrialization is currently a major challenge. It is shown that moisture induces changes in global PSC performance, altering the nature of the absorber through phase transition or segregation. Understanding how the material evolves in a wet environment is crucial for optimizing device performance and stability. Here, the chemical and structural evolution of state-of-the-art hybrid perovskite thin-film Cs0.05 (MA0.15 FA0.85 )0.95 Pb(I0.84 Br0.16 )3 (CsMAFA) is investigated after aging under controlled humidity with analytical characterization techniques. The analysis is performed at different scales through Photoluminescence, X-ray Diffraction Spectroscopy, Cathodoluminescence, Selected Area Electron Diffraction, and Energy Dispersive X-ray Spectroscopy. From the analysis of the degradation products from the perovskite layer and by the correlation of their optical and chemical properties at a microscopic level, different phases such as lead-iodide (PbI2 ), inorganic mixed halide CsPb(I0.9 Br0.1 )3 and lead-rich CsPb2 (I0.74 Br0.26 )5 perovskite are evidenced. These phases demonstrate a high degree of crystallinity that induces unique geometrical shapes and drastically affects the optoelectronic properties of the thin film. By identifying the precise nature of these specific species, the multi-scale approach provides insights into the degradation mechanisms of hybrid perovskite materials, which can be used to improve PSC stability.

Ultraviolet-light–dark cycle analysis of degradation in perovskite solar cells

The stability of perovskite solar cells must be evaluated under realistic outdoor conditions, such as light–dark cycles, because their reversible performance changes under such conditions. Therefore, in this study, we performed light–dark cycle analysis of lead halide perovskite solar cells under ultraviolet (UV) light irradiation to evaluate their metastability and UV degradation. The power drop under UV irradiation was recovered after storing the cells in dark because of ion-migration effects. Furthermore, the energy yield during 6 h of UV irradiation reduced slightly during the light–dark cycles, similar to the reduction in energy yield observed under a white-light-light-emitting diode. This change in energy yield indicates that the power drop observed after 6 h of UV irradiation cannot be attributed to UV-induced degradation of the perovskite used in this study. Our findings show that light–dark cycle analyses are effective for distinguishing between metastability and UV-induced material degradation.

How do carbon dots with amine terminals help perovskite solar cells perform better?

Lead halide perovskite solar cells can be significantly improved with multifunctional additives such as carbon dots (CDs) with amine terminals via defect passivation and band alignment. Here, we determine rational guidelines for the usage of such quantum dots in perovskite solar cells by systematically studying their effects on crystal quality and carrier transport. The amine-terminated CDs homogeneously dispersed in precursors improve the crystal quality of perovskite films, but they reduce the hole mobility hampering hole extraction. In contrast, CDs deposited between the electron transport layer and active layer could promote spin-coated film quality and electron’s extraction efficiently. So, the approaches of the carbon dots in device alters semiconductor properties and energy level structure. Interface engineering achieve better crystal quality and energy level alignment, which in turn affects charge collection, thereby increasing current density and power conversion efficiency. According to the findings of this study, when considering defect passivation by additives, the energy band alignment of the device should also be considered, since this could change carrier dynamics and device performance differently.

Optimization of mixed cation organic–inorganic lead halide perovskite solar cell performance

In this paper, the experimentally studied perovskite solar cell structure, ITO/SnO2/(FAPbI3)[Formula: see text] (MAPbBr[Formula: see text]Cly)x/Spiro-OMeTAD/Au, is considered as our primary cell structure. The Solar Cell Capacitance Simulator is used to investigate the cell performance. The cell performance is obtained after optimizing the influence of layer thickness (open circuit [Formula: see text][Formula: see text]V, short circuit [Formula: see text][Formula: see text]mA/cm2, fill [Formula: see text]%, power conversion [Formula: see text]%). In addition, various inorganic hole transporting layers are incorporated in place of Spiro-OMeTAD to improve cell stability and performance. Finally, with an open circuit [Formula: see text][Formula: see text]V, a short circuit [Formula: see text][Formula: see text]mA/cm2, a fill [Formula: see text]%, and a power conversion efficiency = 19.55%, the optimized cell structure i.e., ITO/SnO2/(FAPbI3)[Formula: see text](MAPbBr[Formula: see text]Cly)x/CulnSe2/Au, performs better. The cell performance is examined in relation to defect density in the absorber layer and at the layer interface. The primary cell results are also validated with the existing experimental results in the literature. This research will pave the way for the development of highly efficient mix-cation perovskite solar cells.

High-Performance Indoor Perovskite Solar Cells by Self-Suppression of Intrinsic Defects via a Facile Solvent-Engineering Strategy.

Lead halide perovskite solar cells have been emerging as very promising candidates for applications in indoor photovoltaics. To maximize their indoor performance, it is of critical importance to suppress intrinsic defects of the perovskite active layer. Herein, a facile solvent-engineering strategy is developed for effective suppression of both surface and bulk defects in lead halide perovskite indoor solar cells, leading to a high efficiency of 35.99% under the indoor illumination of 1000 lux Cool-white light-emitting diodes. Replacing dimethylformamide (DMF) with N-methyl-2-pyrrolidone (NMP) in the perovskite precursor solvent significantly passivates the intrinsic defects within the thus-prepared perovskite films, prolongs the charge carrier lifetimes and reduces non-radiative charge recombination of the devices. Compared to the DMF, the much higher interaction energy between NMP and formamidinium iodide/lead halide contributes to the markedly improved quality of the perovskite thin films with reduced interfacial halide deficiency and non-radiative charge recombination, which in turn enhances the device performance. This work paves the way for developing efficient indoor perovskite solar cells for the increasing demand for power supplies of Internet-of-Things devices.

Raman Spectroscopy of Formamidinium-Based Lead Mixed-Halide Perovskite Bulk Crystals.

In recent years, there has been an impressively fast technological progress in the development of highly efficient lead halide perovskite solar cells. Nonetheless, the stability of perovskite films and associated solar cells remains a source of uncertainty and necessitates sophisticated characterization techniques. Here, we report low- to mid-frequency resonant Raman spectra of formamidinium-based lead mixed-halide perovskites. The assignment of the different Raman lines in the measured spectra is assisted by DFT simulations of the Raman spectra of suitable periodic model systems. An important result of this work is that both experiment and theory point to an increase of the stability of the perovskite structure with increasing chloride doping concentration. In the Raman spectra, this is reflected by the appearance of new lines due to the formation of hydrogen bonds. Thus, higher chloride doping results in less torsional motion and lower asymmetric bending contributing to higher stability. This study yields a solid basis for the interpretation of the Raman spectra of formamidinium-based mixed-halide perovskites, furthering the understanding of the properties of these materials, which is essential for their full exploitation in solar cells.