Materials For Perovskite Solar Cells Research Articles

Structural and photoelectric properties of hybrid halide perovskites CsxMA1-xMgyPb1-yI3 from first-principles

Lead toxicity and stability are important issues to be addressed in organic/inorganic hybrid perovskite solar cell materials. In this study, the electronic, structural, and optical properties of Cs and Mg co-doped organic/inorganic hybrid perovskites were investigated through first-principles calculations. The synergistic effect of (Cs, Mg) doping improves the lattice stability, reduces the content of elemental lead, thereby reducing environmental pollution, and induces a tunable band gap of 0.96–2.58 eV. Perovskite with a bandgap of 1.5–1.6 eV is an ideal adsorbent for solar cells, while that with a bandgap greater than 1.70 eV can be used for perovskite-silicon tandem solar cells. Co-doping of Cs and Mg compresses the neighboring Pb–I and Mg–I bond and distorts the [PbI6] octahedra. The organic/inorganic hybrid perovskites co-doped with cesium and magnesium significantly increase the light absorption coefficients in the near-ultraviolet and visible regions. The predicted Cs and Mg co-doped halide perovskites with intriguing properties would become a promising candidate for applications in solar cells and optoelectronic devices.

Regulation of Intermolecular and Interfacial Interactions by Functionalization of Substituent Groups in Hole Transport Materials for Perovskite Solar Cells: A Density Functional Theory and Experimental Study

Developing potential hole transport materials (HTMs) is an effective approach to reduce carrier nonradiative recombination and improve the efficiency of perovskite solar cells (PSCs). To investigate the intermolecular and interfacial interactions of HTMs in PSC devices, two molecules (RQ7 and RQ8) with substituent group functionalization are designed by isomerizing ‐F and ‐SMe in the para‐ and ortho‐positions on the side chain of carbazole diphenylamine‐based HTMs. Theoretical simulations indicate that the functionalization of substituent groups in HTMs alters their dipole moments and electronic structures, as well as their intermolecular interactions, hole transport capabilities, and interfacial interactions at the HTMs/perovskite interface. Experimental results show that RQ8 exhibited higher hole mobility, better film‐forming ability, and reduced electron‐hole recombination, resulting in RQ8‐based PSC devices achieving a higher power conversion efficiency than those based on RQ7. Herein, it is demonstrated that isomerous functionalization of substituent groups in carbazole diphenylamine‐based HTMs is a feasible strategy for controlling and regulating the intermolecular and interfacial interactions of HTMs in PSC applications.

Overcoming stability challenges in perovskite solar cells: Addressing Li ions movement in Spiro-OMeTAD layer through nano-graphdiyne incorporation

The most used hole transport material in high-performance perovskite solar cells (PSCs) is the lithium compounds-doped 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD). However, PSCs based on the Spiro-OMeTAD suffer from serious instability induced by Li+ migration and aggregation. Herein, nano-graphdiyne (nano-GDY) was incorporated into the Spiro-OMeTAD to retard such free Li+ movement and reduce its impact on device operation stability. We verify that the nano-GDY-modified HTL efficiently enhances carrier transport and promotes favorable energy level alignment compared to that of the control HTL, contributing to improved device performance. Furthermore, the coordination interaction between the nano-GDY and Li+ significantly retrains the Li+ migration into the perovskite and SnO2 layers, and meanwhile, eliminates their aggregation with HTLs under elevated temperature and prolonged light soaking. Consequently, the nano-GDY incorporated PSCs exhibit a champion power-conversion efficiency (PCE) of 24.16 % with negligible hysteresis. Encouragingly, the devices also exhibit robust stability, retaining 97 % and 80 % of peak PCE at maxima power point tracking for 6000 s and continuous illumination for 1080 h, respectively.

End-group modification in a fluorene-terminated efficient hole transport materials for organic and perovskite solar cells

End-group modification in a fluorene-terminated efficient hole transport materials for organic and perovskite solar cells

Cu(II) and Ni(II) Phthalocyanine‐Based Hole‐Transporting Materials for Stable Perovskite Solar Cells with Efficiencies Reaching 20.0%

Herein, Cu(II)Pcs and Ni(II)Pcs peripherally tetra‐functionalized with 5‐hexylthiophene (HT), 5‐hexyl‐2,2′‐bithiophene (HBT), and tertbutyl groups (TB) are readily synthesized and employed as hole‐transporting materials (HTMs) in mixed‐ion perovskite ([FAPbI3]0.85[MAPbBr3]0.15) solar cells, achieving power conversion efficiencies (PCEs) up to 20.0%. Remarkably, both the peripheral functionalization and the central metal are found to play a role in the performance. Through a combination of experimental and theoretical techniques, it is found that the simplest HTM, TB‐CuPc, is the best‐performing HTM primarily due to its higher hole mobility and a more appropriate highest‐occupied molecular orbital, whose enables efficient hole extraction without open‐circuit voltage (Voc)losses. This derivative leads to PCEs of 19.96%, which are among the highest values for Pc‐based HTMs. Importantly, devices incorporating these HTMs present significantly higher stability compared to those based on spiro‐OMeTAD. The results here presented pave the way for more realistic, efficient, and inexpensive photovoltaic devices using phthalocyanine derivatives.

Management of the π-Conjugated System in Carbazole–Diphenylamine Derivative-Based Hole-Transporting Materials for Perovskite Solar Cells: Theoretical Simulation and Experimental Research

Management of the π-Conjugated System in Carbazole–Diphenylamine Derivative-Based Hole-Transporting Materials for Perovskite Solar Cells: Theoretical Simulation and Experimental Research

Reactivity Manipulation of Ionic Liquid Based on Alkyl Primary Ammonium: Protonation Control Using 4‐tert‐Butylpyridine Additive for Effective Spontaneous Passivation of Perovskite via Hole Transport Material Deposition

Alkyl‐primary‐ammonium‐based room‐temperature ionic liquids (RTILs) designed to exhibit specific reactivities allowing functions that cannot be achieved by other RTILs have recently emerged. The archetype of the reactive RTILs is n‐octylammonium bis(trifluoromethanesulfonyl)imide (OA‐TFSI), which has promising functions as an additive for hole transport materials (HTMs) in perovskite solar cells (PSCs); the high reactivity of the OA cations on the perovskite surface allows spontaneous perovskite passivation via HTM deposition, effectively improving the photovoltaic (PV) performance. However, although the reactivity manipulation of the reactive RTILs is instrumental for exploiting their potential functions and exploring their application scope, methods for reactivity control have not been developed. Herein, it is proposed that the coaddition of a pyridine derivative (4‐tert‐butylpridine: TBP) can effectively manipulate the reactivity of OA‐TFSI by controlling the protonation between OA and the 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene (Spiro‐OMeTAD) HTM. The TBP prevents OA deprotonation presumably via stabilization of the OA cation, thus retaining its ammonium form, which allows efficient spontaneous perovskite passivation, effectively enhancing the PV performance. This reveals the protonation preference in the OA‐TFSI system, which is opposite to that in conventional RTILs. This first proposal of a method in manipulating reactivity of the reactive RTILs will contribute to the development of materials science.

Modified SnO2 Electron Transport Layer by One‐Step Doping with Histidine in Perovskite Solar Cells

Tin dioxide (SnO2), one of the best electron transport layer materials for perovskite solar cells (PSCs), has high electrical conductivity and low photocatalytic activity. However, the defects in its inside and surface result in nonradiative recombination at the SnO2/perovskite interface. Complex and time‐consuming passivation methods are not conducive to the commercialization of PSCs, and simple passivation strategies should be used to improve the photovoltaic performance of the devices. Herein, a facile and efficient method is proposed to simultaneously passivate the inside and surface defects by adding histidine (HIS) to SnO2 colloidal solution. This one‐step doping strategy also modulates carrier dynamics at the SnO2/perovskite interface. HIS reduces suspended hydroxyl groups, oxygen vacancies, and uncoordinated Sn4+ defects on the surface of SnO2, as well as uncoordinated Pb2+ and halogen vacancy defects at the buried interface of perovskite. Surprisingly, HIS can prevent perovskite from decomposition to form PbI2, which further decomposes to photoactive metallic Pb0 and I, causing ion migration in PSC. As a result, the PSC efficiency has significantly improved 23.11% after HIS doping. The efficiency of unencapsulated device with HIS is 94% of the primary efficiency after storage in relative humidity = 70 ± 5% for 1000 h.

Curcumin-Assisted Synthesis of MoS2 Nanoparticles as an Electron Transport Material in Perovskite Solar Cells.

Recently, two-dimensional (2D) transition metal dichalcogenides (2D TMDs), such as molybdenum sulfide (MoS2) and molybdenum selenide (MoSe2), have been presented as effective materials for extracting the generated holes from perovskite layers. Thus, the work function of MoS2 can be tuned in a wide range from 3.5 to 4.8 eV by adjusting the number of layers, chemical composition, elemental doping, surface functionalization, and surface states, depending on the synthetic approach. In this proposed work, we attempt to synthesize MoS2 nanoparticles (NPs) from bulk MoS2 using two steps: (1) initial exfoliation of bulk MoS2 into few-layer MoS2 by using curcumin-cholesteryl-derived organogels (BCC-ED) and curcumin solution in ethylene diamine (C-ED) under sonication; (2) ultrasonication of the subsequently obtained few-layer MoS2 at 60-80 °C, followed by washing of the above chemicals. The initial treatment with the BCC-ED/C-ED undergoes exfoliation of bulk MoS2 resulted in few-layer MoS2, as evidenced by the morphological analysis using SEM. Further thinning or reduction of the size of the few-layer MoS2 by prolonged ultrasonication at 60-80 °C, followed by repeated washing with DMF, resulted in uniform nanoparticles (MoS2 NPs) with a size of ~10 nm, as evidenced by morphological analysis. Since BCC-ED and C-ED produced similar results, C-ED was utilized for further production of NPs over BCC-ED owing to the ease of removal of curcumin from the MoS2 NPs. Utilization of the above synthesized MoS2 NPs as an ETL layer in the cell structure FTO/ETL/perovskite absorber/spiro-OMeTAD/Ag enhanced the efficiency significantly. The results showed that MoS2 NPs as an ETL exhibited a power conversion efficiency (PEC) of 11.46%, a short-circuit current density of 18.65 mA/cm2, an open-circuit voltage of 1.05 V, and a fill factor of 58.66%, at the relative humidity of 70 ± 10% (open-air conditions) than that of the ED-treated MoS2 devices without curcumin. These results suggest that the synergistic effect of both curcumin and ED plays a critical role in obtaining high-quality MoS2 NPs, beneficial for efficient charge transport, lowering the crystal defect density/trap sites and reducing the charge recombination rate, thus, significantly enhancing the efficiency.

Theoretical investigation of DMPA-containing carbazole-based hole-transport materials for perovskite solar cells

This study mainly focuses on DFT and TD-DFT modelling and extensive analysis of eight carbazole-based molecules (MM, MPM, MP2.5M, MP2.6M, MP3.5M, MPPM, MP2P2M, and MP3P3M) as Hole Transporting Materials in Perovskite Solar cells. These compounds have in common the arm N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine (M) characterized by its strong ability to carry holes, low cost, and good stability. The molecule MM presents two arms without acceptor core, while other compounds present two arms separated by different acceptor cores: phenyl, biphenyl, pyridine or bipyridine. All under-probe compounds were favored candidates for HTMs in perovskite solar cells due to their excellent HOMO delocalization, reduced hole reorganization energies, lower chemical reactivity, longer radiative lifetimes, and spontaneous solvation processes. Flatness proved beneficial when the core consisted of two cycles, particularly for MP2P2M. The results showed that the HOMO levels were primarily influenced by M fragments in most of the molecules, while the LUMO levels were distributed across both the carbazole units and the cores. All molecules exhibited a more stable LUMO compared to that of Spiro-OMETAD, with MP2P2M showing a notably stable level, resulting in a narrower gap. The study found that, except for MP2P2M, these materials did not interfere with the perovskite layer and effectively filled pores. The incorporation of acceptor core groups improved the conjugation backbone and electronic states, significantly enhancing charge transport properties, particularly in molecules with a double ring structure. Furthermore, adding a pyridine center greatly increased solubility, especially in MP3P3M, suggesting that acceptor core inclusion benefits the solubility of the investigated HTMs. The use of two rings core was shown to enhance light harvesting efficiency, boost photocurrent generation, and improve charge transfer performance, particularly in MP2P2M, which is distinguished by its superior flatness, solubility, and charge transfer properties.

Evaluating Fluorinated-Aniline Units with Functionalized Spiro[Fluorene-9,9'-Xanthene] as Hole-Transporting Materials in Perovskite Solar Cells and Light-Emitting Diodes.

In the field of perovskite optoelectronics, developing hole-transporting materials (HTMs) on the spiro[fluorene-9,9'-xanthene] (SFX) platform is one of the current research focuses. The SFX inherits the merits of spirobifluorene in terms of the configuration and property, but it is more easily derivatized and regulated by virtue of its binary structure. In this work, we design and synthesize four isomeric SFX-based HTMs, namely m-SFX-mF, p-SFX-mF, m-SFX-oF, and p-SFX-oF, through varying the positions of fluorination on the peripheral aniline units and their substitutions on the SFX core, and the optoelectronic performance of the resulting HTMs is evaluated in both perovskite solar cells (PSCs) and light-emitting diodes (PeLEDs) by the vacuum thermal evaporating hole-transporting layers (HTLs). The HTM p-SFX-oF exhibits an improved power conversion efficiency of 15.21% in an inverted PSC using CH3NH3PbI3 as an absorber, benefiting from the deep HOMO level and good HTL/perovskite interface contact. Meanwhile, the HTM m-SFX-mF provides a maximum external quantum efficiency of 3.15% in CsPb(Br/Cl)3-based PeLEDs, which is attributed to its perched HOMO level and shrunken band-gap for facilitating charge carrier injection and then exciton combination. Through elucidating the synergistic position effect of fluorination on aniline units and their substitutions on the SFX core, this work lays the foundation for developing low-cost and efficient HTMs in the future.

Advancing optoelectronic characteristics of Diketopyrrolopyrrole-Based molecules as donors for organic and as hole transporting materials for perovskite solar cells

A stable and efficient hole-transport material (HTM) is crucial for high-performance perovskite solar cells (PSCs). A 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-MeOTAD) being used widely to prepare highly efficient PSCs. However, Spiro-MeOTAD has some limitations due to its complex synthesis, which increases its cost, and it also requires dopants to improve its performance. Therefore, we designed thirteen unique small-molecule-based HTMs (MK1-MK13), which are easy to synthesize, highly cost-effective, and don’t require dopants to prepare efficient PSCs. Their electrical and optical properties are then investigated theoretically using advanced quantum chemical approaches. The designed molecules showed lower energy gaps and improved optical and optoelectronic characteristics because of the improved phase inversion geometry. The detailed photo-physical and optoelectronic characteristics have been studied using density functional theory (DFT) and time-dependent (TD-DFT) calculations. Moreover, we investigated the impact of holes and electrons and the density of states, open-circuit voltage, frontier molecular orbital, transition density matrix, and other structural and photovoltaic characteristics of these materials. Among these, the MK3 molecule possesses the much narrower optical band gap of 1.04 eV and absorbance (λ max) of 684 nm, respectively. In addition, a profound investigation of the MK3/PC61BM blend shows excellent charge transfer at the acceptor–donor interface. Therefore, our proposed technique is necessary for generating appropriate photovoltaic materials for efficient optoelectronic devices and is helpful in further advancing the field.

Effects of palladium doping on structural, mechanical，and opto-electronic behavior of Cs2Pt1-xPdxBr6 double perovskites

Stability in structure and mechanical properties, along with an appropriate band structure, plays a pivotal role in enhancing the performance of the absorber layer materials in perovskite solar cells. In this study, we have employed first-principles calculations to explore the effects of palladium (Pd) doping on the structural, mechanical, and optoelectronic properties of Cs2PtBr6 perovskite. The aim is to explore and identify absorber layer materials for solar cells with superior physical characteristics. Results demonstrated that pristine and Pd4+ doped Cs2PtBr6 are mechanically and dynamically stable, and they all belong to ductile materials. Electronic structure calculations show that Pd4+doping can induce the transition of Cs2PtBr6 from an indirect bandgap to a direct bandgap. Concurrently, with the increase of Pd4+doping concentration, the bandgap decreases, which is beneficial for light absorption. Optical property analyses have also confirmed that with the increase in Pd4+ doping concentration, there is a significant improvement in the optical absorption of Cs2PtBr6 within the visible light range. Particularly, double perovskite Cs2Pt0.25Pd0.75Br6 and Cs2PdBr6 stand out as the best candidates for the solar cell absorption layer due to their close proximity to the ideal bandgap (∼1.5 eV) and strong light absorption coefficients (exceeding 105 cm−1). The findings contribute to the development of light absorption layer materials in perovskite solar cells.

Utilizing a Carbazole‐Incorporated Regioisomeric Synthesis Strategy to Design Hole Transporting Materials for Perovskite Solar Cells

AbstractTwo new p‐type molecules, namely TAT‐TY3 and TAT‐TY4, featuring triazatruxene endcaps and carbazole π‐bridges, were synthesized. The photophysical and electrochemical properties of synthesized materials were comparatively investigated based on their 2,7‐ and 3,6‐carbazole conjugation pathways. Optical characterizations revealed the impact of non‐bonding electron delocalization of triazatruxene through carbazole moieties, resulting in a significant increase in absorption intensity corresponding to n‐π* energy transitions and a red shift of triazatruxene moieties. Consequently, the optical band gaps of TAT‐TY3 and TAT‐TY4 were measured at 3.0 and 3.2 eV, respectively. Moreover, the molecules′ first oxidation potentials exhibited a drastic difference due to the electrochemical behavior of 2,7‐ and 3,6‐carbazole moieties. The highest occupied molecular orbital (HOMO) level for TAT‐TY3 was measured to be −5.02 eV, while for TAT‐TY4, it was measured as −4.67 eV. Hole‐extraction properties were explored using steady‐state and time‐resolved photoluminescence spectroscopy, revealing enhanced charge transfer between the TAT‐TY3/Perovskite interface due to the better alignment of HOMO energy levels. The photovoltaic performances of the hole‐transporting materials (HTMs) were successfully characterized in triple‐cation perovskite solar cells and efficiencies of up to 17.9 %, 16.2 %, and 9.8 % were achieved for Spiro‐OMeTAD, TAT‐TY3, and TAT‐TY4, respectively.

Benzodithiophene‐Based Copolymers as Dopant‐Free Hole‐Transporting Materials for Perovskite Solar Cells

Over a decade, single‐junction perovskite solar cells (PSCs) have achieved a remarkable power conversion efficiency of 26.4%. However, the pressing challenge remains to address their long‐term stability for large‐scale industrial production. A significant factor contributing to this instability is the use of doped hole‐transporting materials (HTMs), which often introduce moisture into contact with the perovskite film, leading to its degradation. To address this issue, research has focused on developing novel and stable “dopant‐free” HTMs. These materials possess inherent conductivity and can function without the need for additional dopants. These HTMs, constructed with donors and acceptors, have properties like film‐forming abilities, tunable molecular weights, unique stacking, and high hole mobility. Among the classic donor units, benzodithiophene (BDT) has emerged as a widely utilized component for the synthesis of molecules and polymers for photovoltaic applications. To stimulate further research and optimization of these materials, this overview presents a comprehensive examination of various BDT‐based dopant‐free polymeric HTMs with different acceptor units within the field of PSCs. It provides a concise historical overview, followed by an in‐depth classification and examination of polymeric structures. The exploration delves into their constituent building blocks, aiming to uncover the relationships between structure and activity wherever feasible.

Critical Review of Cu-Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation.

Despite the remarkable efficiency of perovskite solar cells (PSCs), long-term stability remains the primary barrier to their commercialization. The prospect of enhancing stability by substituting organic transport layers with suitable inorganic compounds, particularly Cu-based inorganic hole-transport materials (HTMs), holds promise due to their high valence band maximum (VBM) aligning with perovskite characteristics. This review assesses the advantages and disadvantages of these five types of Cu-based HTMs. Although Cu-based binary oxides and chalcogenides face narrow bandgap issues, the "chemical modulation of the valence band" (CMVB) strategy has successfully broadened the bandgap for Cu-based ternary oxides and chalcogenides. However, Cu-based ternary oxides encounter challenges with low mobility, and Cu-based ternary chalcogenides face mismatches in VBM alignment with perovskites. Cu-based binary halides, especially CuI, exhibit excellent properties such as wider bandgap, high mobility, and defect tolerance, but their stability remains a concern. These limitations of single anion compounds are insightfully discussed, offering solutions from the perspective of practical application. Future research can focus on Cu-based composite anion compounds, which merge the advantages of single anion compounds. Additionally, mixed-cation chalcogenides such as CuxM1-xS enable the customization of HTM properties by selecting and adjusting the proportions of cation M.

What Should be Considered While Designing Hole-Transporting Material for Perovskite Solar Cells? A Special Attention to Thiophene-Based Hole-Transporting Materials.

The molecular design and conformations of hole-transporting materials (HTM) have unravelled a strategy to enhance the performance of environmentally sustainable perovskite solar cells (PSC). Several attempts have been made and several are underway for improving the efficiency of PSCs by designing an efficient HTM, which is crucial to preventing corrosion, facilitating effective hole transportation, and preventing charge recombination. There is a need for a potential alternative to the current market-dominating HTM due to its high cost of production, dopant requirements, moisture sensitivity, and low stability. Among several proposed HTMs, molecules derived from thiophene exhibit unique behaviour, such as the interaction with under-coordinated Pb2+, thereby facilitating the passivation of surface defects in the perovskite layer. In addition, coupling a suitable side chain imparts a hydrophobic character, eventually leading to the development of a moisture-sensitive and highly stable PSC. Furthermore, thiophene-backboned polymers with ionic pendants have been employed as an interfacial layer between PSC layers, with the backbone facilitating efficient charge transfer. This perspective article comprehensively presents the design strategy, characterization, and function of HTMs associated with thiophene-derived molecules. Hence, it is observed that thiophene-formulated HTMs have an enhanced passivation effect, good performance in an open-circuit environment, longevity, humidity resistance, thermostability, good hole extraction, and mobility in a dopant-free condition. For a better understanding, the article provides a comparative description of the activity and function of thiophene-based small molecules and polymers and their effect on device performance.

Enhanced structural and optical properties of Cs0.1FA0.9PbI3 perovskite thin film with potassium doping for perovskite solar cells

Hybrid halide perovskite (HHP) materials have been rigorously explored since last decade specially for their potential use as absorber layer material in perovskite solar cells. Formamidinium (FA) based HHP materials show many fascinating properties and exhibit thermal stability. However, photoactive cubic phase of formamidinium lead iodide (FAPbI3) material is unstable at room temperature. To overcome the phase stability issue, substitution of Cs+ or MA+ (methylamine) ion has been found useful. Further, to enhance the material properties of FA-MA or FA-Cs based HHP materials, alkali ion doping is widely explored. In this study, the role of K+ ion doping in enhancing the optoelectronic properties of Cs-FA based HHP material is studied thoroughly by structural and optical characterizations. The XRD results show the suppression of yellow non-perovskite phase after Cs doping in FAPbI3 material. The SEM results predict increased grain size with small K+ content in Cs0.1FA0.9PbI3 material. The PL and TRPL results predict the increase in radiative recombination and charge carrier lifetime with small K-doping and detrimental effects of doping concentration above 3 % of K. The solar cell simulation results yield a maximum power conversion efficiency of 18.21 % in K0.03(Cs0.1FA0.9)0.97PbI3 absorbing layer-based device.

Zinc and [Zinc, Nickel]: Co‑doped SnO2 nanoparticles as prospective electron transport layer materials for efficient lead free-MASnI3 perovskite solar cells

In this study, we explore the potential of both pristine and doped tin oxide (SnO2) as promising materials as the electron transport layer (ETL) for efficient lead free-methylammonium tin iodide (MASnI3) perovskite solar cells (PSCs). The pristine, Zinc (Zn) doped, and Nickel (Ni)-Zn co-doped SnO2 nanoparticles with a constant concentration of Zn while changing the concentration of Ni were synthesized by using the hydrothermal method. The effect of doping and co-doping on optical, structural, and electrical properties of SnO2 nanoparticles was investigated using different microscopic and spectroscopic tools. The X-ray diffractograms showed that pristine, doped, and co-doped SnO2 nanoparticles have better crystallinity and tetragonal rutile crystal structure. The fingerprint functional groups and elemental composition were confirmed by FTIR absorption peaks, EDX, and XPS, respectively. The UV–Vis DRS spectroscopy results revealed that the optical band gap reduced from 2.90 eV for pristine SnO2 to 2.26 eV for co-doped 1 wt (wt) % Ni-Zn-SnO2 nanoparticles and can be tuned with a variation of wt % of Ni. Further, the photoluminescence emissions of all SnO2 nanoparticles in the range of 307 to 494 nm are related to oxygen vacancies or defects. Moreover, BET results confirms larger surface area for 1 wt % Ni-Zn-SnO2, which can help in better electron-hole pair separation. The electrical conductivity studies confirm that the synthesized nanoparticles exhibit excellent ohmic contact behavior and show a notable increase in electrical conductivity for 1 wt% Ni-Zn-SnO2 nanoparticles. Further, the suitability of both pristine and doped SnO2 as ETL material for the MASnI3-based PSCs was simulated using SCAPS-1D software. The best power conversion efficiency of 29.60 % was achieved for FTO/1 wt % Ni-Zn-SnO2/MASnI3/Spiro-OMeTAD/Au. This investigation highlights the potential of co-doped materials as promising candidates for the development of efficient PSCs.

‘Exploration of photovoltaic behavior of bithiophene-functionalized dispiro-oxepine based hole-transporting materials for efficient perovskite solar cells’

Perovskite solar cells (PSCs) have received great attention from researchers due to their superior photovoltaic properties, high efficiency, and low cost. In this study, bithiophene dispiro-oxepine based five hole-transporting materials (DDOF1, DDOF2, DDOF3, DDOF4, and DDOF5) are designed by the substitution of end-capped acceptors via thiophene-based bridge to enhance the photovoltaic properties of PSCs. The results showed that designed HTMs have deeper HOMO levels (−4.88 eV to −5.04 eV), high solubility, and compatible stability with lower energy gaps (2.04 eV to 2.59 eV) than the reference (EHOMO = −4.55 eV, Eg = −3.49 eV) and Spiro-OMeTAD (EHOMO = −4.47 eV, Eg = −3.86 eV), which improved hole extraction and the open-circuit voltage in the PSCs. Moreover, the binding energy (0.41 eV to 0.46 eV) and TDM analysis indicated that DDOF1-DDOF5 HTMs have high charge mobility compared to the reference molecule DDOF (0.61 eV). The DDOF1-DDOF5 HTMs indicated anticipated higher power conversion efficiency and open-circuit voltage than the reference molecule. Overall, our findings proved that designed molecules are efficient HTMs for the manufacture of high-efficiency PSCs in the solar industry.