Excellent Photovoltaic Properties Research Articles

Application and Research Progress of Perovskite in the Field of Optoelectronic Materials

Perovskite refers to a class of materials with the formula of ABO3. These oxides were first discovered in calcium titanate compounds. Perovskite materials have attracted widespread attention in the field of contemporary photovoltaic research due to their excellent photovoltaic properties, heralding their potential as protagonists of a new generation of photovoltaic materials. Nevertheless, the stability of perovskite materials needs to be enhanced. In addition, reducing the toxicity of the materials is a key challenge in advancing their commercialization. Currently, the rapid development of perovskite in the field of optoelectronics and its unique combination of properties have laid a solid foundation for its position as a mainstream optoelectronic material of the future. Therefore, this work focuses on the properties and applications of perovskite optoelectronics. With deeper scientific research and technological innovation, perovskites have the potential to overcome existing limitations and move towards large-scale commercial production. In the future, the further application of perovskite optoelectronic materials would have far-reaching implications for the global energy transition and environmental protection.

Roles of defects in perovskite CsPbX3 (X=I, Br, Cl): a first- principles investigation

Inorganic lead halide perovskite CsPbX3 (X=I, Br, Cl) have a promising application in optoelectronic fields due to their excellent photovoltaic properties. The defects, which have a significant impact on the performance of materials, are often introduced during the synthesis process. However, there is still a lack of systematic theoretical investigation of the effects of these defects. In this study, the effects of vacancies and H-atom interstitial point defects on the structural, electronic and optical properties of CsPbX3 are systematically investigated by using first-principles approach based on density-functional theory. The calculated results show that the introduction of different defects have significantly effect on the band gap, effective mass, semiconductor properties, ion migration and optical absorption coefficient of the perovskite materials. It is also found that VCs and VPb defects introduce shallow transition levels that do not negatively impact the optoelectronic properties. However, VX and interstitial H defects generate deep transition levels within the bandgap, which acts as non-radiative recombination centers and reduce the optoelectronic performance of the perovskite material. This study contributes to the understanding of the nature of halide chalcogenides and optimally regulating the performance of optoelectronic devices.

Optimizing the performance of Inverted FASnI3-based perovskite solar cells by device simulation

Abstract The tin-based PSCs (perovskite solar cells), with low toxicity and excellent photovoltaic properties, offer a promising solution to lead environmental pollution and toxicity issues, emerging as a strong substitute for environmentally friendly lead-free PSCs. However, tin-based PSCs still face significant challenges in terms of low power conversion efficiency and poor long-term stability. Therefore, in-depth research on tin-based PSCs is required to further enhance their performance. In this study, we utilize SCAPS-1D to simulate the currently efficient inverted FASnI3-based PSCs and determine the PSCs device parameters that are as close as possible to the results in published experiments. The simulation results indicate that the parameter adjustment of the absorption layer plays a vital role in the inverted device. Those parameters are thickness, defect density, and doping concentration. Similarly, parameter variations of other layers (parameters such as electron affinity, thickness, and doping concentration) and interfaces (parameters are defect density at different interfaces) are considered. We achieve a final optimized simulated device power conversion efficiency of 18.219%. This research aims to contribute to the future development of inverted FASnI3-based PSCs.

Prediction of the photovoltaic performance of the lead-free layered Ruddlesden–Popper organic–inorganic perovskite (CH3NH3)2GeI4

Using the density functional theory (DFT) and the spectral limited maximum efficiency (SLME) model, we thoroughly evaluate the material MA2GeI4 as a prospective absorber for photovoltaic applications. This material belongs to the family of layered material organic-inorganic Ruddlesden-Popper perovskites, which have attracted interest due to their stability. Our first-principles calculations show that MA2GeI4 has a direct bandgap that is suitable for light absorption at 1.37 eV. To understand the source of its exceptional optical properties, the electronic structure, density of states, and optical properties were examined. Also, we used the SLME model to estimate the MA2GeI4 solar cell efficiency. The latter was found to be about 32.6% power conversion efficiency. The material’s excellent absorption and promising photovoltaic properties contribute to its high efficiency, even when quantum confinement occurs between layers. We found that MA2GeI4 is a potential absorber material for solar applications, demonstrating both good absorption characteristics and advantageous electrical properties. This discovery lays the path for additional experimental investigation of MA2GeI4 based solar cell.

Layer-controllable synthesis, lattice structural Determination, and fluorescence lifetime imaging of (HA)2(MA)n-1PbnI3n+1 Quasi-2D organic-inorganic perovskite microsheets

Hybrid quasi-two-dimensional (quasi-2D) perovskites have attracted great interest due to their excellent photovoltaic and light-emitting properties, which enable the rapid development of high-performance perovskite-based solar cells, light-emitting diodes, and lasers. Although many efforts have been made to improve the quality and stability of organic-inorganic perovskites, the controlled synthesis of high-quality layered perovskites remains challenging. Here, single-crystalline quasi-2D (HA)2(MA)n-1PbnI3n+1 perovskites with layer numbers of n from 1 to 3 have been synthesized in a controllable manner, exhibiting stable lattice structures and tunable optical emission. Structurally, hexylamine (HA) with longer alkyl chains was used as an organic spacer in Ruddlesden-Popper (RP) phase perovskites to improve the chemical stability of perovskites. Various ratios of precursor materials were adopted for separating pure and large-scale quasi-2D (HA)2(MA)n-1PbnI3n+1 perovskites, in which different layer-number perovskites with tunable band gaps were obtained with the modulated fluorescence lifetimes. Our lattice structural and fluorescence-lifetime characterizations of RP-phase perovskites provide critical information on the emerging quasi-2D perovskite-crystal systems and their fluorescence relaxation dynamics. The employed strategy to synthesize high-quality perovskites (HA)2(MA)n-1PbnI3n+1 is technically essential to develop the rising perovskite-based photovoltaic and light-emitting applications.

Effects of Surface Defects on Performance and Dynamics of CsPbI2Br Perovskite: First-Principles Nonadiabatic Molecular Dynamics Simulations.

Inorganic mixed-halogen perovskites exhibit excellent photovoltaic properties and stability; yet, their photoelectric conversion efficiency is limited by inherent surface defects. In this work, we study the impact of defects on properties of CsPbI2Br slabs using first-principles calculations, focusing on specific defects such as I vacancy (VI), I interposition (Ii), and I substitution by Pb (PbI). Our findings reveal that these defects affect the geometric and optoelectronic properties as well as dynamics of charge carriers of slabs. We employ two theoretical frameworks (surface hopping and Redfield theory) of nonadiabatic molecular dynamics simulations to comprehensively study relaxation processes and obtain consistent results. The presence of VI reduces carrier lifetimes, while the influence of PbI on carrier lifetimes is negligible. In contrast, Ii defects lead to prolonged carrier lifetimes. These insights provide valuable guidance for the rational design of perovskite photovoltaic devices, aiming to enhance their efficiency and stability.

Review on Preparation of Perovskite Solar Cells by Pulsed Laser Deposition

Pulsed laser deposition (PLD) is a simple and extremely versatile technique to grow thin films and nanomaterials from a wide variety of materials. Compared to traditional fabrication methods, PLD is a clean physical vapour deposition approach that avoids complicated chemical reactions and by-products, achieving a precise stochiometric transfer of the target material onto the substrate and providing control over the film thickness. Halide perovskite materials have attracted extensive attention due to their excellent photoelectric and photovoltaic properties. In this paper, we present an overview of the fundamental and practical aspects of PLD. The properties and preparation methods of the halide perovskite materials are briefly discussed. Finally, we will elaborate on recent research on the preparation of perovskite solar cells by PLD, summarize the advantages and disadvantages of the PLD preparation, and prospect the all-vacuum PLD-grown solar cells in a full solar cell structure.

Electronic structures of lead-free Sn- or Ge-hybrid perovskite halides studied by first-principles calculation

Although CH3NH3PbI3-based perovskite compounds have excellent photovoltaic properties, the lead (Pb) is harmful to the environment, and Pb-free perovskite compounds are needed for next generation solar cells. Theoretical calculations could be one of the good methods to design the Pb-free compounds, and the first-principles calculation was used to predict the properties of the present proposed materials. The instability of organic molecules such as CH3NH3 is also a problem, and alkali elements such as cesium and rubidium could improve the stability. From these point of view effects of tin (Sn) or germanium (Ge) on the lead-free Cs- or Rb- -based perovskites including double perovskite structures were investigated by first-principles calculation in the present work. For the standard single perovskite structures, perovskites with chlorine have suitable band gap energies, higher electron mobilities, and photovoltaic performance compared with other iodine or bromine-based perovskites. For the double perovskite structures, bromine was found to be the suitable halogen, and Ge provided a higher electron density than Sn. The double perovskite structures also provided wider band gap energies and improved stability compared with the standard single perovskites, and the photovoltaic properties could be affected by hybridization of Sn/Ge or halogen ions.

A theoretical study of all-inorganic perovskite solar cells: Computational modeling of the CsPbI[formula omitted]/RbGeI[formula omitted] bilayer absorber structure

All-inorganic perovskite solar cells (AI-PSCs) have garnered significant attention in the perovskite community due to their stability and efficient photogeneration and absorption capabilities. Despite the toxicity associated with all-inorganic CsPbI3 perovskites containing lead (Pb), its presence remains crucial for achieving excellent photovoltaic properties. However, the imperative shift towards AI-PSCs using less toxic materials with suitable photovoltaic properties is imperative. The incorporation of a double perovskite absorber layer allows for broadening the absorption spectrum of PSCs and enhancing cell stability. In this study, we propose a novel AI-PSC structure with CsPbI3 as the top absorber with a wide bandgap of 1.69 eV and a lead-free RbGeI3 perovskite as the bottom absorber layer with a low bandgap of 1.31 eV. Utilizing numerical simulations with the SCAPS-1D simulator, we analyze the photovoltaic parameters of AI-PSCs with single and double absorber layers. Our investigations reveal that a double absorber layer structure, comprising CsPbI3 and RbGeI3 materials, outperforms a single-junction PSC based on CsPbI3. By optimizing critical device parameters, we achieved an impressive efficiency of 31.91% in an AI-PSC device with a CsPbI3(0.6 μm)/RbGeI3(2 μm) bilayer configuration. This study positions lead-free RbGeI3 perovskite as a promising partner for CsPbI3, offering a potential pathway for the development of highly efficient AI-PSCs.

Synthesis, crystal structure, thermal stability, and photovoltaic properties of organic-inorganic hybridized copper-based perovskite single crystals modulated by organics

Organic-inorganic hybridized perovskite have excellent photovoltaic properties, especially Pb-based organic-inorganic perovskite polycrystalline thin films based on Pb-based organic-inorganic perovskite have achieved high power conversion efficiency, but the polycrystalline materials have a large number of grain boundaries and defects, which are susceptible to the influence of water and oxygen, leading to structural degradation, poor stability, high toxicity and slow degradation, which are not friendly to the environment. Therefore, in this paper, two copper-based organic-inorganic hybrid perovskite single crystals (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 were synthesized by using the method of organic modulation, and were investigated by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis, and UV–vis diffuse reflectance spectroscopy. The samples were analyzed in detail for crystal structure, chemical groups, bond characterization, optical and thermal stability. The results show that (C6H9N2)2CuCl4 and (C6H18N2)2Cu2Cl8 single crystals belong to the C2/c space group of the monoclinic crystal system and the P-1 space group of the triclinic crystal system, respectively. The optical band gap of (C6H9N2)2CuCl4 is 2.45 eV, which is stable up to 179 °C, and that of (C6H18N2)2Cu2Cl8 is 2.47 eV, which is stable up to 163 °C. The thermal stability of the crystals can be regulated by changing the organic cation in the A-site, but the optical band gap of the crystals cannot be regulated significantly.

Nanosheet thickness control of nitrogen-doped polyimide/ammonium phosphotungstate composite for photocatalytic mineralization of imidacloprid

A series of polyimide/ammonium phosphotungstate composite photocatalysts were prepared by varying the the amine monomers, including melamine (MAPIPW), melem (MEPIPW), and carbon nitride (CNPIPW). As the heterocycle in these molecules gets larger, the nano-layer thickness reduces progressively. This results in an increased specific surface area for those photocatalysts possessing thin layers. For instance, the specific surface areas recorded for MAPIPW, MEPIPW and CNPIPW are 8.1863, 51.3379, and 142.6756 m2/g respectively. Thanks to their high surface areas, these composites exhibited improved substrate adsorption and demonstrated significant enhancement in imidacloprid degradation rates increasing to 70.06%, 76.39%, and 71.39% for MAPIPW, MEPIPW, and CNPIPW respectively. MEPIPW exhibited the highest degradation efficiency due to its superior physical adsorption, besides exhibiting excellent photovoltaic properties. An intricate POM-π interaction exists between polyimide and the Keggin structure of ammonium phosphotungstate, extending ligand conjugation to this framework so as to disperse electrons across the hybrid material's backbone. Nonetheless, this interaction may be weakened with reduced nano-sheet thickness, impacting composite photon absorption ability. Further enhancing photocatalysis was possible via nitrogen doping using urea, resulting in degradation rates of 93.69%, 95.13%, and 91.39%, for MAPIPW-20%U, MEPIPW-20%U and CNPIPW-20%U respectively.

Self-powered high-performance UV–vis–IR hybrid photovoltaic photodetector based on Epilobium angustifolium L. (Onagraceae)

Water-soluble Epilobium angustifolium (EA) extract was successfully coated on n-type Si single crystal by spin coating method to obtain EA/n-Si heterojunction device. UV–vis absorption and SEM analysis of the EA film were performed and the optical band gap was calculated as 2.71 eV. Electro-optical measurements of the fabricated device were performed and was found to give very good photoresponse in the UV–vis-IR regions. According to the experimental results, the EA/n-Si heterojunction showed not only high-performance photodetector properties but also self-driven properties under visible light as well as under UV and IR lights. At 150 mW/cm2 visible light, the device demonstrated excellent photovoltaic properties with Voc and Isc values of 0.40 V and 4.65 A, respectively. Under IR light, the responsivity, specific detectivity and NPDR reached 0.65 A/W and 1.41 × 1012 Jones, 4.23 × 108 W−1 respectively. Finally, a high-performance organic/inorganic photodetector in the broadband range has been successfully fabricated.

In-Situ Polymer Framework Strategy Enabling Printable and Efficient Perovskite Solar Cells by Mitigating "Coffee Ring" Effect.

Organic-inorganic hybrid perovskites are considered ideal candidates for future photovoltaic applications due to their excellent photovoltaic properties. Although solution-printed manufacturing has shown inherent potential for the low-cost, high-throughput production of thin-film semiconductor electronics, the high-quality and high-reproducibility deposition of large-area perovskite remains a bottleneck that restricts their commercialization due to the droplet coffee-ring effect (CRE). In this study, these issues are addressed by introducing an in situ polymer framework. The 3D framework formed by spontaneous cross-linking improves the precursor viscosity and homogenizes its heat diffusion coefficient, counteracting the lateral capillary flow of the colloidal particles and anchoring their flocculent movement. Thus, the Marangoni convection intensity is properly controlled to ensure high-quality perovskite films, which significantly enhances reproducibility in printing efficient photovoltaics by mitigating the CRE. Subsequently, the perovskite solar cells and modules achieve power conversion efficiencies of 23.94 and 17.53%, and exhibit positive environmental stability, retaining over 90 and 78% efficiency after storage for 2500 and 1600h, respectively. This work may serves as a foundation for exploring precursor rheology to match the homogeneous deposition requirements of perovskite photovoltaics and facilitating the advancement of their printing manufacturing and commercialization transition.

Molecular engineering of D-π-A-type structures based on nitrobenzofurazan (NBD) derivatives for both organic solar cells and nonlinear optical response

The electronic, photo-physical, and nonlinear optical (NLO) properties of small molecules from nitrobenzofurazan (NBD) derivatives have been fine-tuned through the introduction of various electron-donating groups (OH, OCH3, and N(CH3)2). These designed small molecules follow a donor-linker-acceptor (D-π-A) motif, featuring p-phenylene as the electron donor, thiophene as the π-conjugated bridge, and NBD as the electron acceptor. To achieve this, we conducted density functional theory (DFT) and its time-dependent counterpart, TD-DFT calculations. Our exploration of the structure–property relations among the molecular parameters revealed that the introduction of donor groups has a notable influence on lowering the highest occupied molecular orbital (HOMO) energy levels. Analysis of the absorption–emission spectra showed a prominent π → π* band followed by a weaker n → π* band.Remarkably, three compounds substituted with electron-donor group’s exhibit anti-Stokes fluorescence (ASF) emission. Moreover, the relatively weak emission band associated with the charge transfer n → π* transition of the nitro-functionalized molecules is quenched, similar to the π → π* electronic transition. Consequently, these compounds display a lower bandgap energy, resulting in a broad optical absorption profile with emissions spanning from green to yellow. Notably, when tuning the NLO properties, push-type groups exhibit demonstrate exceptionally high hyperpolarizabilities. Furthermore, our investigation unveiled excellent photovoltaic properties, with these compounds achieving an impressive power conversion efficiency (PCE) of approximately 7 %.Additionally, we conducted complementary topological analyses, including Molecular Electrostatic Potential (MEP), Quantum Theory of Atoms in Molecules (QTAIM), Reduced Density Gradient (RDG), Electron Localization Function (ELF), and the Localized Orbital Locator (LOL), to gain insights into both intra- and intermolecular interactions. These findings strongly underscore the effectiveness of modifying the electron-donating group capability in D-π-A conjugated systems as a strategy for enhancing the optoelectronic properties of organic photovoltaic (PV) devices, as well as their NLO responses.

Photo‐catalytic Performance of MAPbI3/g‐C3N4 for Efficient Hydrogen Production under Visible Light

AbstractRecently, hydrogen (H2) production via photocatalytic process has been received enormous attention of the scientific community globally. Perovskite materials such as methyl ammonium lead iodide (MAPbI3) has excellent photovoltaic and photocatalytic properties and may be a promising photocatalyst for H2 production reaction. In this paper, we have designed and synthesized MAPbI3 perovskite embedded graphitic carbon nitride (MAPbI3@g‐C3N4) composite via benign approaches. The phase and crystalline nature was authenticated by powder X‐ray diffractometer. Morphological characteristics of the MAPbI3@g‐C3N4 composite was further checked by scanning electron microscope. The elemental composition and valence states of the MAPbI3@g‐C3N4 was determined by X‐ray photoelectron spectroscopy (XPS). Furthermore, MAPbI3@g‐C3N4 has been explored as photocatalyst for H2 production reaction using hypophosphorous acid (H3PO2) as stabilizing agent. Platinum (Pt) has been used as co‐catalyst. The reasonably good amount of H2 of 21.25 μmol/g was produced using MAPbI3 as photocatalyst. Further, improved H2 amount of 939.4 μmol/g was produced using MAPbI3@g‐C3N4. The MAPbI3@g‐C3N4 exhibited decent H2 production rate of 93.94 μmol/h/g. The excellent stability of the MAPbI3@g‐C3N4 offers its potential applications for reusable studies. This work proposed the potential application of MAPbI3@g‐C3N4 towards H2 generation applications.

Preparation of wide-bandgap perovskite thin films by propylamine hydrochloride assisted gas quenching method

Perovskite is a material with excellent photovoltaic properties, and the efficiency of perovskite solar cells has increased rapidly in recent years. By utilizing the adjustable bandgap characteristics of perovskite materials, wide-bandgap perovskite solar cells can be combined with narrow-bandgap solar cells to make tandem solar cells. Tandem devices can improve the utilization of the solar spectra and achieve higher power conversion efficiency. An important prerequisite for preparing efficient photovoltaic devices is to fabricate high-quality perovskite active layers. Antisolvent-assisted spin-coating is currently a commonly used method for preparing high-quality perovskite films in the laboratory. However, the low solubility of inorganic cesium and bromine salts in the preparation of wide-bandgap perovskite thin films leads to a fast crystallization rate, poor crystallization quality and a large number of defects, seriously reducing the photovoltaic performance of the devices. In addition, the antisolvent has a narrow working window, which is not conducive to the preparation of large-area perovskite films. In this work, a mild gas quenching process is used to assist the spin-coating method in preparing wide-bandgap perovskite films, and propylamine hydrochloride is introduced as an additive to improve the crystallization quality and uniformity of large-area preparation of perovskite film. The interaction between the propylamine cation and the perovskite component produces a two-dimensional perovskite phase. Two-dimensional phase is used as the growth template for perovskite composition in order to reduce the formation energy of <i>α</i>-phase perovskite, which is beneficial to uniform nucleation and preferential orientation growth of perovskite, the increase of grain size and the decrease of grain boundaries within the film. The improvement of the crystalline quality of the perovskite film can reduce the defect density inside the film and suppress the non-radiative recombination of the photogenerated carriers. The perovskite solar cell with a bandgap of 1.68 eV, prepared by using this strategy, achieves a power conversion efficiency of 21.48%. In addition, the 8 cm×8 cm wide-bandgap perovskite films prepared by this method exhibit good uniformity. This work provides a strategy for developing the process of efficient and large-area perovskite photovoltaic devices.

Low-temperature synthesis of porous organic polymers with donor-acceptor structure and β-ketoenamine for photocatalytic oxidative coupling of amines.

In light of the widespread use of fossil fuels and the resulting environmental pollution, it is crucial to develop efficient photocatalysts for renewable energy applications that utilize visible light. Organic photocatalysts based on β-ketoenamine offer several advantages, including facile preparation, high stability, structural controllability, and excellent photovoltaic properties. However, in previous studies, the synthesis of porous organic polymers (POPs) often involved long, high-temperature processes. In this study, POPs with donor (D)-acceptor (A) structure were constructed by utilizing various branched bridging groups and 2,4,6-triformylphloroglucinol, across multiple temperature gradients. Through adjustments in hydrothermal temperature, we successfully synthesized a series of POPs with varying enol-keto structure ratios. Among these POPs, the dimethoxybenzidine-POPs (DMDPOPs) with methoxy electron-rich branched chains exhibited superior photovoltaic performance, electron transfer rate, and photocatalytic activity compared to the dihydroxybenzidine-POPs (DHDPOPs) with electron-deficient hydroxyl branched chains. Notably, DMDPOP-30 demonstrated outstanding performance, achieving a conversion rate of 98% within 3 h. Additionally, other POPs exhibited favorable conversions (90%), further confirming the feasibility of this synthetic approach. Moreover, the synthesis of DMDPOP-30 was achieved under mild conditions at room temperature, highlighting its significant potential for practical applications.

Enhancing broadband blue luminescence efficiency and stability in Bi3+-doped Cs2ZnCl4 nanocrystals from STEs and advancing energy applications

Lead-halide perovskites exhibit excellent photovoltaic properties.

Multidentate anchoring strategy for synergistically modulating crystallization and stability towards efficient perovskite solar cells

CsFAMA-based perovskite solar cells (PSCs) have become promising photovoltaic materials due to their excellent photovoltaic properties. However, the inherent instability of perovskite severely hinders its commercialization, since the typical ionic nature of perovskite can cause the ionic migration and volatilization of organic components. Herein, allantoin molecules with multiple alternating carbonyl (C = O) and amino (–NH2 or –NH–) groups were introduced as a multidentate additive to synergistically anchor the perovskite components and passivate the defects, resulting in non-radiative recombination and ion migration being not susceptible to occur. Due to the favorable attraction ability of allantoin to the perovskite precursor monomers and the formation of hydrogen bonds between FAI/MAI and allantoin, the crystal quality of perovskite was significantly improved and the bulk/interface defects were effectively eliminated. Specifically, the interaction between allantoin and FA+/MA+ can suppress their deprotonations and prevent the volatilization of organic cations from the initial precursor solutions, drastically reducing the wastage of precursor materials. Consequently, the modified devices demonstrated a prominent elevation of performance with a higher efficiency of 21.49 %, which was better than that of control (19.67 %). Moreover, the modified perovskite films also demonstrated prominent stability under the continuous illumination and moisture aging owing to the reduction of trap defects. The allantoin additives also greatly enhanced the hydrophobicity of perovskite, and the modified device maintained 90 % of its initial efficiency for 1680 h at 10–20 % relative humidity without encapsulation.

Mechanism of Tunable Band Gap of Halide Cubic Perovskite CsPbBr3−xIx

Perovskites are organic-inorganic compounds with a crystal structure that revolutionize many optoelectronic applications, especially solar cells. The CsPbBr3−xIx, a perovskite, has garnered significant attention due to its tunable band gap and excellent photovoltaic properties. In this theoretical study, the structural, electronic, and optical properties of CsPbBr3−xIx are investigated through density functional theory calculations. The calculations reveal that the substitution of Br with I leads to a significant reduction in the band gap of CsPbBr3−xIx, resulting in improved light absorption properties. The obtained data show that the coexistence of Br and I ions in the structure creates an energy level similar to the shallow energy levels caused by doping at the R symmetry point in the band structure.