I3 Perovskite Research Articles

Theoretical investigations on the electronic and optical properties of Na-doped CH3NH3PbI3 perovskite

The development of important materials for photovoltaic applications is rapidly advancing, particularly in the field of perovskite materials. This study investigates the optical and electronic characteristics of CH 3 NH 3 Pb I3 and analyzes the influence of doping in perovskite CH 3 NH 3 Pb I3 with different concentrations of sodium ions Na+. In this study, we employed Density Functional Theory to assess the optical and electronic properties of both pure and Na+ ion-doped CH 3 NH 3 Pb I3, with Na+ concentrations of 12.5 %, 25 %, and 37.5 %. The bandgap energy of pure CH 3 NH 3 Pb I3 rises from 1.205 eV to 1.573 eV as the concentration of Na+ ions increases from 0 % to 37.5 %, respectively. Doping with Na+ ions leads to an increase in the absorption coefficient of pristine CH 3 NH 3 Pb I3 perovskite in both UV and visible ranges. Doping likewise affects the density of states, dielectric function, and the refractive index of CH 3 NH 3 Pb I3 material. These findings offer vital insights into modulating the electronic and optical characteristics of CH 3 NH 3 Pb I3 through Na+ ion doping.

Comparative Study of the Correlation between Diffusion Length of Charge Carriers and the Performance of CsSnGeI3 Perovskite Solar Cells

Due to their enhanced performance and simplicity in manufacturing, scalability, and versatility, lead-halide perovskite-based solar cells (HPSCs) have received much attention in the domains of energy. Lead is present in nature as a poisonous substance that causes various issues to climate and human health and prevents its further industrialization. Over the past few years, there has been a noticeable interest in exploring some alternative lead-free perovskites. However, owing to some intrinsic losses, the performance that may be achieved from these photovoltaics is not up to standards. Thus, for the purpose of efficiency improvement, a comprehensive simulation is required to comprehend the cause of these losses. In the current research, an investigation into how to employ the promisingly efficient lead-free, all-inorganic cesium tin–germanium iodide (CsSnGeI3) perovskites as the photoactive layer in HPSCs was performed. Results exhibited a high efficiency of 12.95% with a CsSn0.5Ge0.5I3 perovskite thickness of 0.6 μm and a band gap of 1.5 eV at room temperature. High efficiency may be achieved using phenyl-C61-butyric acid methyl ester (PCBM) as an electron transport material because of its favorable energy-level alignment with the perovskite material. The research further tested the perovskite layer thickness and defect density in depth. The results showed that the carrier diffusion lengths have a big effect on how well the HPSC works.

Integrated Ideal‐Bandgap Perovskite/Bulk‐Heterojunction Solar Cells with Efficiencies > 24%

Here, the authors report a highly efficient integrated ideal-bandgap perovskite/bulk-heterojunction solar cell (IPBSC) with an inverted architecture, featuring a near infrared (NIR) polymer DTBTI-based bulk-heterojunction (BHJ) layer atop guanidinium bromide (GABr)-modified FA0.7 MA0.3 Pb0.7 Sn0.3 I3 perovskite film as the photoactive layer. The IPBSC shows cascade-like energy level alignment between the charge-extractionlayer/perovskite/BHJ and efficient passivation effect of BHJ on perovskite. Thanks to the well-matched energy level alignment and high-quality ideal bandgap-based perovskite film, an efficient charge transfer occurs between the charge-extraction-layer/perovskite/BHJ. Moreover, the NIR polymer DTBTI on the perovskite film leads to an improved NIR light response for the IPBSC. In addition, the O, S and N atoms in the DTBTI polymer yield a strong interaction with perovskite, which is conducive to reducing the defects of the perovskite and suppressing charge recombination. As a result, the solar cell achieves a power conversion efficiency (PCE) of 24.27% (certificated value at 23.4% with 0.283-volt voltage loss), currently the recorded efficiency for both IPBSCs and Pb-Sn alloyed PSCs, and which is over the highest efficiency of perovskite-organic tandem solar cell. Moreover, the thermal, humidity and long-term operational stabilities of the IPBSCs are also significantly improved compared with the control PSCs.

Improving the efficiency of solar cells based on CsSn0.5Ge0.5I3 perovskite by using ZnO nanorods

Subject of study. Environmentally friendly tin and germanium-based halide perovskite materials are promising candidates attracting more attention as lead-free halide perovskite solar cells. However, the limited power conversion efficiency of these perovskites is an important issue in the solar cells field. Therefore, in the present study, a different lead-free perovskite was used to reach higher power conversion efficiency. Devices with an indium tin oxide/electron transport layer/perovskite/hole transport layer/Ag structure but different absorber layers were simulated. Simulation was done using the Solar Cell Capacitance Simulator (SCAPS-1D) to investigate the photovoltaic performance of solar cells with CsGeI3 and CsSnI3 perovskites as the absorber layer. Method. Simulation was done by using the SCAPS software, which is a one-dimensional solar cell simulation platform developed at the Department of Electronics and Information Systems of the University of Gent, Belgium. Main results. The effect of the absorber layer thickness was investigated, and a maximum power conversion efficiency of 10.51% was obtained for 1000 nm thick CsGeI3, while the maximum value of 12.83% was obtained for 400 nm thick CsGeI3. Then, to further increase the efficiency, devices with an alternative lead-free CsSn0.5Ge0.5I3 perovskite including a planar ZnO layer and ZnO nanorod arrays as electron transport layers was used in the simulation, and the thickness of the absorber layer was optimized for both devices. For the maximum power conversion efficiency of the devices, the values of 17.56% and 22.61% were achieved for devices with a ZnO layer and ZnO nanorods, respectively. It is noted that the simulation results of this study could provide a perspective towards fabricating an environmentally friendly perovskite-based solar cell. Practical significance. The main significance of the present work is obtaining a significant power conversion efficiency of 22.61% for a device based on environmentally friendly perovskite. Similar work was done in 2021 by M. Azadinia et al. [Mater. Today Energy20, 100647 (2021)10.1016/j.mtener.2021.100647], in which a comparable power conversion efficiency of 26.9% was reported for a device with CsSn1−xGexI3 perovskite.

Influence of Photon Pump Fluence on Charge Carriers in FAPbI3 and Manganite Perovskites

FAPbI3 and FA(Mn:Pb)I3 perovskite films were prepared and evaluated through steady and transient absorption spectroscopy. According to the analysis using Elliot’s model, there were no considerable differences except for the absorption intensity between FAPbI3 and FA(Mn:Pb)I3 perovskite films: the value of the optical gap (Eg) and the position of exciton resonance (E0) were the same. The femtosecond transient absorption showed biexponential relaxation properties of the charge carriers, suggesting that biexcitons are more easily generated in FA(Mn:Pb)I3 than FAPbI3 perovskite. The generation of biexcitons in FA(Mn:Pb)I3 was also confirmed by the photon pump fluence dependence. Moreover, we were able to estimate the average number of absorbed photons directly from the photon pump power dependence without needing any further experimental measurements such as photoluminescence. Our findings may offer a new way of understanding photoinduced carrier dynamics in perovskite manganites.

Numerical study of lead free CsSn0.5Ge0.5I3 perovskite solar cell by SCAPS-1D

Lead free perovskite solar cells (PCS) are becoming a distinctly predominant area of study due to the toxicity and stability hurdles of the lead halide perovskite. Current lead-free perovskites are also plagued with low efficiency. This work is concerned with the design and analysis of CsSnGeI3 that is a viable competitor to lead based perovskites by SCAPS-1D simulator (ver.3.3.08). The primary solar cell’s structure is FTO/PCBM/ CsSn0.5Ge0.5I3 / spiro-OMeTAD/Au which achieved a power conversion efficiency (PCE) of 7.11% [1]. To enhance device performance, the effect of optimizing absorber layer defect density (1 × 1015 cm−3) and thickness (700–800 nm), doping concentration of absorber layer (1 × 1015 cm−3), variation of Electron Transport Material (ETL) and Hole Transport Material (HTL) parameters (effect of CBO and VBO and doping concentration) and potential material options for ETL and HTL are studied. The results of the simulation are as follows; maximum power conversion efficiency (PCE) 18.79%, short circuit current density (Jsc) 27.05 mA/cm2, open circuit voltage (Voc) 0.87 V and fill factor (FF) 79.25%. By choosing appropriate material parameters, improving fabrication and encapsulation processes, CsSn0.5Ge0.5I3 proves to be an environmentally friendly solar cell with high efficiency.

Double‐Side Crystallization Tuning to Achieve over 1 µm Thick and Well‐Aligned Block‐Like Narrow‐Bandgap Perovskites for High‐Efficiency Near‐Infrared Photodetectors

AbstractSolution‐processed narrow‐bandgap Sn–Pb perovskites have shown their potential in near‐infrared (NIR) photodetection as a promising alternative to traditional silicon and inorganic compounds. To achieve efficient NIR photodetection, high‐quality Sn–Pb perovskite thick films with well‐packed, smooth, and pinhole/void‐free features are highly desirable for boosting the spectral absorption. Understanding the crystallization kinetics and tuning the crystallization are fundamentally important to reach such high‐quality thick Sn–Pb perovskite films, and have been limitedly explored. Herein, an approach of double‐side crystallization tuning through low‐temperature space‐restricted annealing in methylammonium‐free Sn–Pb perovskite films with over 1 µm thickness is proposed. More specifically, through simultaneously retarding the crystallization in the top of precursor films and promoting the crystal growth of the bottom of precursor films, high‐quality and block‐like thick FA0.85Cs0.15Sn0.5Pb0.5I3 perovskite films with improved crystallinity, preferred out‐of‐plane orientation, and reduced trap density are achieved. Finally, photovoltaic‐mode Sn–Pb perovskite NIR photodetectors show a high external quantum efficiency of ≈80% at 760–900 nm, a recorded responsivity of 0.53 A W−1, and a high specific detectivity of 6 × 1012 Jones at 940 nm. This study offers the fundamental understanding of the crystallization kinetics of thick perovskite films and paves the way for perovskite‐based emerging NIR photodetection and imaging applications.

High-performance methylammonium-free ideal-band-gap perovskite solar cells

Summary The development of mixed tin-lead (Sn-Pb)-based perovskite solar cells (PSCs) with low band gap (1.2–1.4 eV) has become critical not only for pushing single-junction devices toward the maximum efficiency given by the Shockley-Queisser limit, but also for enabling all-perovskite tandem devices beyond this limit. However, achieving high power-conversion efficiency (PCE) and long-term device operation stability simultaneously remains a significant challenge for Sn-Pb-based PSCs. Here, we demonstrate near ideal-band-gap (∼1.34 eV) methylammonium-free Sn-Pb-based PSCs with high efficiency (∼20%) and promising operational stability of maintaining >80% of initial PCE over 750 h under maximum-power-point tracking. The key to this success is the use of a SnCl2⋅3FACl complex additive that improves the microstructure and reduces the development of residual stress in the Sn-Pb perovskite thin films, which in turn enhances the efficiency and stability of the Sn-Pb-based ideal-band-gap PSCs.

Effects of doping with Na, K, Rb, and formamidinium cations on (CH3NH3)0.99Rb0.01Pb0.99Cu0.01I3−x(Cl, Br)x perovskite photovoltaic cells

The effects of doping with alkali metals and formamidinium cations on CH3NH3(Rb)Pb(Cu)I3(Cl,Br) perovskite photovoltaic cells were investigated. Lattice constants were slightly decreased and increased by K and Na doping, respectively. This indicated that Na atoms occupied interstitial sites in the perovskite crystal. The conversion efficiencies for most of the devices decreased after one year. However, the conversion efficiency for the CH3NH3(Na,Rb)Pb(Cu)I3(Cl,Br) photovoltaic cell was unchanged after one year. The Na-doped perovskite provided the smallest carrier trap density, which suggested that lattice defects were suppressed by Na doping. First principles calculations supported these experimental results.

Topotactic transition of Pb0.99Bi0.01I2 into CH3NH3Pb0.99Bi0.01I3 on TiO2 for high-performance visible light perovskite photodetector

In this article, we report the fabrication of self-powered CH3NH3Pb0.99Bi0.01I3 perovskite visible light photodetector by chemical vapour deposition. The crystalline Pb0.99Bi0.01I2 layer grown on TiO2 nanoarrays (NAs) was transformed into trap free CH3NH3Pb0.99Bi0.01I3 functional perovskite layer by exposure of methylamine iodide at various time intervals. The TiO2 NAs improve the morphology and growth of crystalline CH3NH3Pb0.99Bi0.01I3 layers which increases the charge transport and exciton dissociation. Self-powered device resulted in the high photocurrent density of 9.01 × 10−4, 2.65 × 10−3 and 7.06 × 10−3 mA/cm2 under the irradiation of simulated visible solar light at various power densities of 30, 60 and 90 mW/cm2, respectively. The dark current of 10−4 mA/cm2 at 0.3 V clearly evidences ultra-low charge carrier recombination in the bilayer photodetector device. The device accomplishes very good photoresponsivity of ~10−4 AW−1 under self-powered condition.

Understanding the Film Formation Kinetics of Sequential Deposited Narrow‐Bandgap Pb–Sn Hybrid Perovskite Films

AbstractDeveloping efficient narrow bandgap Pb–Sn hybrid perovskite solar cells with high Sn‐content is crucial for perovskite‐based tandem devices. Film properties such as crystallinity, morphology, surface roughness, and homogeneity dictate photovoltaic performance. However, compared to Pb‐based analogs, controlling the formation of Sn‐containing perovskite films is much more challenging. A deeper understanding of the growth mechanisms in Pb–Sn hybrid perovskites is needed to improve power conversion efficiencies. Here, in situ optical spectroscopy is performed during sequential deposition of Pb–Sn hybrid perovskite films and combined with ex situ characterization techniques to reveal the temporal evolution of crystallization in Pb–Sn hybrid perovskite films. Using a two‐step deposition method, homogeneous crystallization of mixed Pb–Sn perovskites can be achieved. Solar cells based on the narrow bandgap (1.23 eV) FA0.66MA0.34Pb0.5Sn0.5I3 perovskite absorber exhibit the highest efficiency among mixed Pb–Sn perovskites and feature a relatively low dark carrier density compared to Sn‐rich devices. By passivating defect sites on the perovskite surface, the device achieves a power conversion efficiency of 16.1%, which is the highest efficiency reported for sequential solution‐processed narrow bandgap perovskite solar cells with 50% Sn‐content.

Near-Infrared Emission from Tin-Lead (Sn-Pb) Alloyed Perovskite Quantum Dots by Sodium Doping.

Phase-stable CsSnx Pb1-x I3 perovskite quantum dots (QDs) hold great promise for optoelectronic applications owing to their strong response in the near-infrared region. Unfortunately, optimal utilization of their potential is limited by the severe photoluminescence (PL) quenching, leading to extremely low quantum yields (QYs) of approximately 0.3 %. The ultra-low sodium (Na) doping presented herein is found to be effective in improving PL QYs of these alloyed QDs without alerting their favourable electronic structure. X-ray photoelectron spectroscopy (XPS) studies suggest the formation of a stronger chemical interaction between I- and Sn2+ ions upon Na doping, which potentially helps to stabilize Sn2+ and suppresses the formation of I vacancy defects. The optimized PL QY of the Na-doped QDs reaches up to around 28 %, almost two orders of magnitude enhancement compared with the pristine one.

Reversible Ultra-Slow Crystal Growth of Mixed Lead Bismuth Perovskite Nanocrystals: The Presence of Dynamic Capping.

An ultra-slow crystal growth over a period of 24 h of a newly synthesized CH3 NH3 Pb1/2 Bi1/3 I3 perovskite (MPBI) nanocrystal in non-polar toluene medium is reported here. From several spectroscopic techniques as well as from TEM analysis we found that the size of nanocrystals changes continuously with time, in spite of being capped by the ligands. Using a single molecular spectroscopic technique, we also found that this size change is not due to the stacking of nanocrystals but due to crystal growth. The notable temperature dependence and reversible nature of the nanocrystals growth is explained by the dynamic nature of the capping. The observed temperature-dependent ultra-slow growth is believed to be a pragmatic step towards controlling the size of perovskite NC in a systematic manner.

Sub-1.4eV bandgap inorganic perovskite solar cells with long-term stability

State-of-the-art halide perovskite solar cells have bandgaps larger than 1.45 eV, which restricts their potential for realizing the Shockley-Queisser limit. Previous search for low-bandgap (1.2 to 1.4 eV) halide perovskites has resulted in several candidates, but all are hybrid organic-inorganic compositions, raising potential concern regarding device stability. Here we show the promise of an inorganic low-bandgap (1.38 eV) CsPb0.6Sn0.4I3 perovskite stabilized via interface functionalization. Device efficiency up to 13.37% is demonstrated. The device shows high operational stability under one-sun-intensity illumination, with T80 and T70 lifetimes of 653 h and 1045 h, respectively (T80 and T70 represent efficiency decays to 80% and 70% of the initial value, respectively), and long-term shelf stability under nitrogen atmosphere. Controlled exposure of the device to ambient atmosphere during a long-term (1000 h) test does not degrade the efficiency. These findings point to a promising direction for achieving low-bandgap perovskite solar cells with high stability.

All-Inorganic CsCu2 I3 Single Crystal with High-PLQY (≈15.7%) Intrinsic White-Light Emission via Strongly Localized 1D Excitonic Recombination.

Energy-saving white lighting from the efficient intrinsic emission of semiconductors is considered as a next-generation lighting source. Currently, white-light emission can be composited with a blue light-emitting diode and yellow phosphor. However, this solution has an inevitable light loss, which makes the improvement of the energy utilization efficiency more difficult. To deal with this problem, intrinsic white-light emission (IWE) in a single solid material gives a possibility. Here, an all-inorganic lead-free CsCu2 I3 perovskite single crystal (SC) with stable and high photoluminescence quantum yield (≈15.7%) IWE through strongly localized 1D exciton recombination is synthesized. In the CsCu2 I3 , the Cu-I octahedron, which provides most of electron states, is isolated by Cs atoms in two directions to form a 1D electronic structure, resulting a high radiation recombination rate of excitons. With this electronic structure design, the CsCu2 I3 SCs have great potential in energy-saving white lighting.

Sn‐Pb Binary Perovskite Films with High Crystalline Quality for High Performance Solar Cells

Summary of main observation and conclusionAs an environmentally friendly perovskite material with low bandgap, Tin (Sn)‐based perovskite has drawn much attention. A simple and effective method for fabricating high‐quality Sn‐Pb binary perovskite film is highly desired. Here, with methylammonium chloride (MACl) post‐treatment to assist vertical recrystallization, we fabricated high quality FA0.75Cs0.25Pb0.5Sn0.5I3 perovskite film via one‐step processing method. This recrystallization method was first used in Sn‐based perovskite. The obtained film consists of vertically aligned grains with high crystallinity, which contributes to a power conversion efficiency (PCE) of 14.03% in corresponding perovskite solar cell (PVSC). The cells maintained 80% of their initial PCEs after being stored for 30 d in glove‐box. This simple, effective method provides an easy way to fabricate high performance Sn‐Pb binary PVSC.

Electronic Structures and Magnetic Properties of Transition Metal Doped CsPbI3 Perovskite Compounds by First-Principles Calculation

Transition metal doped cesium lead halide (CsPbI3) perovskite compounds were studied for application in photovoltaic solar cells. Electronic structures, chemical shifts of 207Pb and 127I-NMR, vibration modes in infrared and Raman spectra of transition metals (Mn2+, Fe2+ or Cu2+)-doped CsPbI3 perovskite compounds were studied by the first-principles calculation using density functional theory. The CsPb(Fe)I3 perovskite crystals had a slight perturbation of crystal field in the coordination structure. The electron density distribution was delocalized on the 5p orbital of I atom, the 3d orbital of Fe atom and the 6p orbital of Pb atom. The first excited process was based on ligand metal charge transfer from the 5p orbital on I atom to the 3d orbital of Fe atom. The chemical shifts of 127I-NMR were associated with the electron correlation of electron-nuclear spin interaction and nuclear quadrupole interactions based on electron field graduate. The asymmetric vibrations of Pb–I bonds stretching mode related to electron conductivity with scattering of the carrier diffusion as phonon effectiveness. The slight perturbation of the coordination structure in the CsPb(Fe)I3 perovskite crystal will improve the photovoltaic and optical properties.

Low-bandgap mixed tin–lead iodide perovskite with large grains for high performance solar cells

Low-bandgap (1.26 eV) FA0.7MA0.3Sn0.3Pb0.7I3 perovskite film with vertically aligned large grains and high crystallinity was fabricated via a two-step processing method on top of a hydrophobic PTAA HTL. A maximum PCE of 13.6% was obtained with negligible current–voltage hysteresis.

Defect Passivation via a Graded Fullerene Heterojunction in Low-Bandgap Pb–Sn Binary Perovskite Photovoltaics

Development of low-bandgap (∼1.2 eV) Pb–Sn binary perovskites is exciting and has recently gained immense attention because of their high photovoltages, lowered Pb toxicity, and pivotal role in realizing perovskite tandem solar cells. Defect passivation in this class of perovskite alloys has immense potential to further reduce the photovoltage deficit but is relatively unexplored. Here, we investigate and report the passivation of defect sites in low-bandgap CH3NH3Pb0.5Sn0.5I3 perovskite through the incorporation of fluoroalkyl-substituted fullerene (DF-C60) via a graded heterojunction (GHJ) structure. Graded distribution of DF-C60 successfully reduced the number of trap sites, and the resultant films had characteristically lower Urbach energy, dominant bimolecular recombination, and higher surface/bulk recombination resistance. The improved optoelectronic quality of films with GHJ structure was reflected in improved performance for corresponding photovoltaic devices, with the best PCE up to 15.61% and a ...

C60 additive-assisted crystallization in CH3NH3Pb0.75Sn0.25I3 perovskite solar cells with high stability and efficiency.

The development of hybrid tin (Sn)-lead (Pb) perovskite solar cells likely tackles the toxic problem with the power conversion efficiency (PCE) exceeding 17%. However, the stability problems, e.g. hysteresis effect, degeneration and oxidation, appear to be the bottleneck that limit its further development. Here, we innovatively introduced C60 at the grain boundaries throughout the CH3NH3Pb0.75Sn0.25I3 (MAPb0.75Sn0.25I3) thin film, playing a role not only in in situ passivating the interfaces and reducing the pinholes of perovskite thin films, but also in preventing the penetration of moisture and oxygen from ambient atmosphere. Electrochemical impedance spectroscopy (EIS) illustrated that the recombination lifetime of both the bulk and surface of MAPb0.75Sn0.25I3 thin films was increased by additive incorporation of C60. Dark I-V results for the electron/hole-only devices showed that the charge trap-state density decreased with C60 additive incorporated into the hybrid Sn-Pb perovskite thin films. Importantly, the hybrid Sn-Pb perovskite solar cells modified with C60 additive were demonstrated to have superior stability and efficiency when exposed to the ambient environment without encapsulation.