Promising Power Conversion Efficiency 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.

Multi‐Selenophene Strategy Enables Dimeric Acceptors‐Based Organic Solar Cells with over 18.5% Efficiency

AbstractDimeric acceptor (DMA) becomes a promising alternative to small‐molecular and polymeric acceptor‐based organic solar cells (OSCs) due to its well‐defined chemical structure, high batch‐to‐batch reproducibility, and low molecular diffusion properties. However, DMAs usually exhibit blueshifted absorptions, limiting their photon utilization abilities. Herein, multi‐selenophene strategies are adopted to develop redshifted DMAs. From monomer (YSe) to dimers (DYSe‐1 and DYSe‐2), reduced electron reorganization energies and exciton binding energies enable the efficient charge dynamics in the DMAs‐based OSCs. Together with their effective absorption extending to ≈920 nm, DYSe‐1‐ and DYSe‐2‐ based OSCs exhibit outstanding short‐circuit current densities (JSCs) over 27 mA cm−2, which are the best among DMAs. Besides, compared with the YSe‐based device, both DMA‐based devices have higher electroluminescence quantum efficiencies and thus reduce nonradiative recombination loss (ΔE3), contributing to their reduced energy losses. The resultant open‐circuit voltages (VOCs) of DYSe‐1‐ and DYSe‐2‐ based OSCs are ≈0.88 V, which, combining their super JSC values, lead to the promising power conversion efficiencies of 18.56% and 18.22%, respectively. These results are among the best in DMAs‐based OSCs and highlight the great potential of the multi‐selenophene strategy for the development of redshifted DMAs with high performance.

Anti-Solvent-Free Fabrication of Stable FA0.9Cs0.1PbI3 Perovskite Solar Cells with Efficiency Exceeding 24.0% through a Naphthalene-Based Passivator.

The anti-solvent-free fabrication of high-efficiency perovskite solar cells (PSCs) holds immense significance for the transition from laboratory-scale to large-scale commercial applications. However, the device performance is severely hindered by the increased occurrence of surface defects resulting from the lack of control over nucleation and crystallization of perovskite using anti-solvent methods. In this study, 2-(naphthalen-2-yl)ethylamine hydriodide (NEAI) is employed as the surface passivator for perovskite films without using any anti-solvent. Naphthalene demonstrates strong π-π conjugation, which aids in the efficient extraction of charge carriers. Additionally, the naphthalene-ring moieties form a tight attachment to the perovskite surface. After NEAI treatment, FA and I vacancies are selectively occupied by NEA+ and I- in NEAI respectively, thus effectively passivating the surface defects and isolating the surface from moisture. Ultimately, the optimized NEAI-treated device achieves a promising power conversion efficiency (PCE) of 24.19% (with a certified efficiency of 23.94%), featuring a high fill factor of 83.53%. It stands out as one of the reported high PCEs achieved for PSCs using the spin-coating technique without the need for any anti-solvent so far. Furthermore, the NEAI-treated device can maintain ≈87% of its initial PCE after 2000h in ambient air with a relative humidity of 30%±5%.

Boosting optoelectronic performance of (FA)X(MA)1-XPbI3 perovskite solar cells: Via FAI post-treatment engineering

Complex composition engineering of mixed-cations perovskite (FAxMA1-xPbI3) has recently supported rapid progress in perovskite solar cells (PSCs). Nevertheless, it is insufficient to embed and accommodate formamidinium (FA) cation into the MAPbI3 lattice structure via existing methods, leaving behind masses of FA or lead halide content and deteriorating photovoltaic performance. Herein, we present facile surface engineering via post-treated methodology, the surface of CH3NH3PbI3 (MAPbI3) films post-treated with formamidinium iodide (FAI) solution and that results get mixed-cation FAxMA1-xPbI3 perovskite films. The mixed-cation-based FAXMA1-XPbI3 perovskite with significant and large grain size, uniform and compact morphology, highly crystallization, and consequently reducing defect density of the perovskite films can be produced via the present method. It is observed that the film, post-treated with FAI-2, shows results in a very stable and highly crystalline lattice structure with attributes such as extended carrier lifetime, better electron transport, and decreased defect density. The optimized device demonstrates a promising power conversion efficiency (PCE) of 21.89%, and higher than that of the non-treated (19.08%) devices. Furthermore, the devices based on the novel FAI-post-treatment engineering exhibit significantly enhanced stability compared to non-treated devices. Therefore, this approach provides a novel methodology that offers a simple method for producing superior mixed perovskite films, potentially paving the way for the future exploitation of the boosted performance of perovskite solar cells.

Over 19 % Efficiency Organic Solar Cells Enabled by Manipulating the Intermolecular Interactions through Side Chain Fluorine Functionalization.

Fluorine side chain functionalization of non-fullerene acceptors (NFAs) represents an effective strategy for enhancing the performance of organic solar cells (OSCs). However, a knowledge gap persists regarding the relationship between structural changes induced by fluorine functionalization and the resultant impact on device performance. In this work, varying amounts of fluorine atoms were introduced into the outer side chains of Y-series NFAs to construct two acceptors named BTP-F0 and BTP-F5. Theoretical and experimental investigations reveal that side-chain fluorination significantly increase the overall average electrostatic potential (ESP) and charge balance factor, thereby effectively improving the ESP-induced intermolecular electrostatic interaction, and thus precisely tuning the molecular packing and bulk-heterojunction morphology. Therefore, the BTP-F5-based OSC exhibited enhanced crystallinity, domain purity, reduced domain spacing, and optimized phase distribution in the vertical direction. This facilitates exciton diffusion, suppresses charge recombination, and improves charge extraction. Consequently, the promising power conversion efficiency (PCE) of 17.3 % and 19.2 % were achieved in BTP-F5-based binary and ternary devices, respectively, surpassing the PCE of 16.1 % for BTP-F0-based OSCs. This work establishes a structure-performance relationship and demonstrates that fluorine functionalization of the outer side chains of Y-series NFAs is a compelling strategy for achieving ideal phase separation for highly efficient OSCs.

Over 19 % Efficiency Organic Solar Cells Enabled by Manipulating the Intermolecular Interactions through Side Chain Fluorine Functionalization

AbstractFluorine side chain functionalization of non‐fullerene acceptors (NFAs) represents an effective strategy for enhancing the performance of organic solar cells (OSCs). However, a knowledge gap persists regarding the relationship between structural changes induced by fluorine functionalization and the resultant impact on device performance. In this work, varying amounts of fluorine atoms were introduced into the outer side chains of Y‐series NFAs to construct two acceptors named BTP‐F0 and BTP‐F5. Theoretical and experimental investigations reveal that side‐chain fluorination significantly increase the overall average electrostatic potential (ESP) and charge balance factor, thereby effectively improving the ESP‐induced intermolecular electrostatic interaction, and thus precisely tuning the molecular packing and bulk‐heterojunction morphology. Therefore, the BTP‐F5‐based OSC exhibited enhanced crystallinity, domain purity, reduced domain spacing, and optimized phase distribution in the vertical direction. This facilitates exciton diffusion, suppresses charge recombination, and improves charge extraction. Consequently, the promising power conversion efficiency (PCE) of 17.3 % and 19.2 % were achieved in BTP‐F5‐based binary and ternary devices, respectively, surpassing the PCE of 16.1 % for BTP‐F0‐based OSCs. This work establishes a structure‐performance relationship and demonstrates that fluorine functionalization of the outer side chains of Y‐series NFAs is a compelling strategy for achieving ideal phase separation for highly efficient OSCs.

Two‐dimensional Bimetal‐Embedded Expanded Phthalocyanine Monolayers: A Class of Multifunctional Materials with Fascinating Properties

AbstractThe expanded phthalocyanine (EPc) single‐layer sheets with embedded double transition metals (labeled as TM2EPc) are predicted to be a novel class of highly stable 2D materials with a series of fascinating properties by means of systematic first‐principles calculations, molecular dynamics, and Monte Carlo simulations. Excitingly, the ferromagnetic Cr2EPc and antiferromagnetic Mn2– and Fe2–EPc have high magnetic transition temperatures of 223 (TC), 217 (TN), and 325 K (TN), respectively. This makes them promising candidates for low‐dimensional spintronic applications. Unexpectedly, V2EPc is an antiferromagnetic metal with Dirac cone, while ferromagnetic Cr2EPc exhibits Dirac half‐metallicity. The ultra‐high Fermi velocities near Dirac cones render them promising candidates for applications in high‐speed nanoelectronics and spintronics. Several architectured type‐II heterojunctions show promising power conversion efficiency with maximum 25.19% for Ni2EPc/2H‐WSe2, which has great potential in excitonic solar cell applications. Diverse promising properties endow this class of materials multifunction, which paves the way towards the future applications in nanoelectronics, spintronics, optoelectronics, and photovoltaics.

Polydentate Ligand Reinforced Chelating to Stabilize Buried Interface toward High-Performance Perovskite Solar Cells.

The instability of the buried interface poses a serious challenge for commercializing perovskite photovoltaic technology. Herein, we report a polydentate ligand reinforced chelating strategy to strengthen the stability of buried interface by managing interfacial defects and stress. The bis(2,2,2-trifluoroethyl) (methoxycarbonylmethyl)phosphonate (BTP) is employed to manipulate the buried interface. The C=O, P=O and two -CF3 functional groups in BTP synergistically passivate the defects from the surface of SnO2 and the bottom surface of the perovskite layer. Moreover, The BTP modification contributes to mitigated interfacial residual tensile stress, promoted perovskite crystallization, and reduced interfacial energy barrier. The multidentate ligand modulation strategy is appropriate for different perovskite compositions. Due to much reduced nonradiative recombination and heightened interface contact, the device with BTP yields a promising power conversion efficiency (PCE) of 24.63 %, which is one of the highest efficiencies ever reported for devices fabricated in the air environment. The unencapsulated BTP-modified devices degrade to 98.6 % and 84.2 % of their initial PCE values after over 3000 h of aging in the ambient environment and after 1728 h of thermal stress, respectively. This work provides insights into strengthening the stability of the buried interface by engineering multidentate chelating ligand molecules.

Polydentate Ligand Reinforced Chelating to Stabilize Buried Interface toward High‐Performance Perovskite Solar Cells

AbstractThe instability of the buried interface poses a serious challenge for commercializing perovskite photovoltaic technology. Herein, we report a polydentate ligand reinforced chelating strategy to strengthen the stability of buried interface by managing interfacial defects and stress. The bis(2,2,2‐trifluoroethyl) (methoxycarbonylmethyl)phosphonate (BTP) is employed to manipulate the buried interface. The C=O, P=O and two −CF3 functional groups in BTP synergistically passivate the defects from the surface of SnO2 and the bottom surface of the perovskite layer. Moreover, The BTP modification contributes to mitigated interfacial residual tensile stress, promoted perovskite crystallization, and reduced interfacial energy barrier. The multidentate ligand modulation strategy is appropriate for different perovskite compositions. Due to much reduced nonradiative recombination and heightened interface contact, the device with BTP yields a promising power conversion efficiency (PCE) of 24.63 %, which is one of the highest efficiencies ever reported for devices fabricated in the air environment. The unencapsulated BTP‐modified devices degrade to 98.6 % and 84.2 % of their initial PCE values after over 3000 h of aging in the ambient environment and after 1728 h of thermal stress, respectively. This work provides insights into strengthening the stability of the buried interface by engineering multidentate chelating ligand molecules.

Semicrystalline Unfused Polymer Donors with Backbone Halogenation toward Cost‐Effective Organic Solar Cells†

Comprehensive SummaryDeveloping novel unfused building blocks with simple synthesis and low cost is essential to advance and enrich cost‐effective polymer donors; however, it remains a challenge due to the lack of efficient molecular strategies. Herein, a class of low‐cost and fully unfused polymer donors with precisely regulated backbone planarity via halogenation was designed and synthesized, namely PDTBTBz‐2H, PDTBTBz‐2F, and PDTBTBz‐2Cl. These polymer donors possess a four‐step synthesis route with over 80% yield from cheap raw chemicals comparable to existing low‐cost polymer donors, such as PTQ10. Benefitting from the planar backbone via incorporating the F···S non‐covalent interactions, PDTBTBz‐2F exhibits more robust J‐type aggregation in solution and a long‐ranged molecular stacking in film relative to PDTBTBz‐2H and PDTBTBz‐2Cl. Moreover, the systematical study of PDTBTBz‐based organic solar cells (OSCs) reveals the close relationship between optimized molecular self‐assembly and charge separation/transport regarding backbone halogenation when paired with the non‐fullerene acceptor (Y6‐BO‐4F). As a result, the photovoltaic devices based on semicrystalline PDTBTBz‐2F achieved a promising power conversion efficiency (PCE) of 12.37%. Our work highlighted the influence of backbone halogenation on the molecular self‐assembly properties and a potential unfused backbone motif for further developing cost‐effective OSCs.

Integration of Metal Meshes as Transparent Conducting Electrodes into Perovskite Solar Cells

AbstractAs the demand for photovoltaic technologies continues to grow, the quest for efficient and sustainable transparent conducting electrodes (TCEs) rapidly rises. Traditional solutions, such as indium tin oxide (ITO), face challenges related to indium scarcity and environmental impact. To tackle these issues, a novel metal mesh rear TCE consisting of gold micro‐meshes is developed as ITO replacement in perovskite solar cells (PSCs). This study reveals that optimized Au meshes can guarantee 75% of the extracted photocurrent compared to reference devices with ITO and a promising power conversion efficiency (PCE) of 8.65%. By utilizing hybrid mesh structures with a 10‐nm ITO layer, the PCE further improves to 12.1%, with the extracted current exceeding 80% of the reference. Metal meshes can even serve to replace the opaque metal contact of PSCs, amplifying their functionality and efficiency through bifacial and multi‐junction applications. Here, aerosol jet‐printed silver meshes serve as front electrodes, combined with either 5–10 nm of Au, achieving efficient semi‐transparent devices (PCE 16.8%), or with 5–10 nm of ITO, providing enhanced bifacial properties while maintaining competitive efficiency. Overall, this work highlights remarkable features of metal meshes, making them promising alternatives to commonly used TCEs in optoelectronic applications.

Controlling Lead Halide Residue in Perovskite Solar Cells: A Method to Improve the Photostability and Hysteresis

The presence of residual lead iodide phase in perovskite films, inherent to the two‐step spin‐coating method, has been reported to be beneficial for the performance of perovskite solar cells (PSCs); However, it may potentially undermine the photostability of PSCs. Herein, four distinct sets of perovskite films and devices are fabricated via the two‐step spin‐coating process, each under different processing conditions. All conditions demonstrate promising power conversion efficiency in PSCs. However, the aspect of photostability is found to be significantly influenced by unreacted PbI2 in the perovskite films. Varying degrees of residual PbI2 are detected among these films. Upon light exposure, it is observed that residual PbI2 within perovskites undergoes decomposition into metallic lead (Pb0) and mobile iodine, and these can affect the photovoltaic performance of the PSCs. The presence of mobile ions in metal–halide perovskites has generated substantial concern due to their impact on hysteresis within the J–V curve. Furthermore, the metallic lead (Pb0) containing perovskite films exhibits a prominent inverted hysteresis in the J–V curve

Over 18% Efficiency Ternary Organic Solar Cells with 300nm Thick Active Layer Enabled by an Oligomeric Acceptor.

The development of high-efficiency thickness-insensitive organic solar cells (OSCs) is crucially important for the mass production of solar panels. However, increasing the active layer thickness usually induces a substantial loss in efficiency. Herein, a ternary strategy in which an oligomer DY-TF is incorporated into PM6:L8-BO system as a guest component is adopted to break this dilemma. The S···F intramolecular noncovalent interactions in the backbone endow DY-TF with a high planarity. Upon the addition of DY-TF, the crystallinity of the blend is effectively improved, leading to increased charge carrier mobility, which is highly desirable in the fabrication of thick-film devices. As a result, thin-film PM6:L8-BO:DY-TF-based device (110nm) shows a power conversion efficiency (PCE) of 19.13%. Impressively, when the active layer thickness increases to 300nm, an efficiency of 18.23% (certified as 17.8%) is achieved, representing the highest efficiency reported for 300 nm thick OSCs thus far. Additionally, blade-coated thick device (300nm) delivers a promising PCE of 17.38%. This work brings new insights into the construction of efficient OSCs with high thickness tolerance, showing great potential for roll-to-roll printing of large-area solar cells.

Density-of-state engineering of conjugated polymers by implanting partial two-dimensional conjugation: Broad absorption and high performing organic photovoltaics

Uniform and broad absorption characteristics are fundamental for improving the light-harvesting capabilities of organic photovoltaics (OPVs). A partial two-dimensional (2D) conjugated structure is formed by introducing additional conjugation in the transverse direction of the main backbone of conjugated polymers (CPs). This alters the bimodal-shaped absorption spectrum of typical donor–acceptor CPs to a trimodal-shaped profile by modulating the density of energy states, enabling uniform absorption characteristics in the visible region. The uniform and broad absorption properties of CPs can be confirmed by the proportional improvement in the short-circuit current density (JSC) and external quantum efficiency (EQE) in OPVs. In particular, when a CP with modified absorption characteristics is blended with a non-fullerene acceptor (Y6) that can absorb light in the near-infrared (NIR) region, the CP:Y6 blend exhibits a uniform light-harvesting capability from the visible to NIR regions through complementary absorption between the CP and Y6. This results in a promising power-conversion efficiency (PCE) of 16.13 % with a JSC of 27.83 mA·cm−2 and fill factor (FF) of 75.22 %. Finally, the morphological effects that determine the charge-recombination properties of the CP:Y6 blends are systematically characterized. The results confirm that the film morphology, in which small domains are uniformly formed, partly contributes to FF enhancement.

Potential application of Ce doped NiO green synthesised from husk of Cocos nucifera in various types of DSSCs

ABSTRACT In this study, a complete green synthesis procedure was approached to prepare two semiconductor oxide materials NiO and Ce-doped NiO in nanoscale, and natural dyes were extracted from the husk of tender coconut. To our knowledge, this is a novel work that reports Ce-doped NiO synthesized from husk of tender coconut. Coconut is being cultivated in more than 97 countries, and India contributes to 50% of its global production. After consumption of the nutritious liquid from the tender coconut, 33–35% of the fruit (mesocarp and endocarp) are being dumped as agro-wastes. In order to make capital of this wastes, they were utilized in fabricating different types of dye-sensitized solar cells (DSSCs). With the extracted natural dyes, and Rhodamine B, six DSSCs were made with NiO and Ce:NiO and two tandem structured DSSCs were devised with TiO2 as one layer and synthesized NiO materials being the other layer. Tandem cell made with TiO2 and Ce:NiO resulted in the promising power-conversion efficiency of 0.165% and the cell made with TiO2 and NiO exhibited an efficiency of 0.06%.

New Molecular Design, Step-Saving Synthesis, and Applications of Indolocarbazole Core-Based Oligo(hetero)arenes.

In this work, we have successfully synthesized 15 new examples (LLA01-06; LinLi01-10) of small-molecule hole-transporting materials (HTM) using the less explored indolocarbazole (ICbz) as core moiety. Different from previously reported ICbz HTMs, LinLi01-10 exhibit new molecular designs in which 3,4-ethylenedioxythiophene (EDOT) units are inserted as crucial π-spacers and fluorine atoms are introdcued into end-group molecules. These substantially improve the materials solubility and device power conversion efficiencies (PCEs) while fabricated in perovskite solar cells (PSC). More importantly, LinLi01-10 are generated by a sustainable synthetic approach involving the use of straightforward C-H/C-Br couplings as key transformations, thus avoiding additional synthetic transformations including halogenation and borylation reactions called substrate prefunctionalizations usually required in Suzuki reactions. Most HTM molecules can be purified simply by reprecipitations instead of conducting column chromatography. In contrast to LLA01-06 without additional EDOT moieties, PSC devices using LinLi01-10 as hole-transport layers display promising PCEs of up to 17.5%. Interestingly, PSC devices employing seven of the LinLi01-10 as hole-transport molecules, respectively, are all able to show an immediate >10% PCE (t = 0) without any device oxidation/aging process that is necessary for the commercial spiro-OMeTAD based PSCs.

High-Performance Nonfused Electron Acceptor with Precisely Controlled Side Chain Fluorination.

Modification of the molecular packing of nonfullerene acceptors through fluorination represents one of the most promising strategies to achieve highly efficient organic solar cells (OSCs). In this work, three nonfused electron acceptors, namely, DTCBT-Fx (x = 0, 5, 9) with precisely controlled amounts of fluorine atoms in the side chains are designed and synthesized, and the effect of side chain fluorination is systematically studied. The results demonstrate that the light absorption, energy levels, molecular ordering, and film morphology could be effectively tuned by precisely controlling the side chain fluorination. DTCBT-F5 with an appropriate fluorine functionalization exhibits suitable miscibility with the donor polymer (PM6), leading to diminished charge recombination and improved charge carrier mobility. Consequently, a promising power conversion efficiency of 12.7% was obtained for DTCBT-F5-based solar cells, which outperforms those OSCs based on DTCBT-F0 (11.4%) and DTCBT-F9 (11.6%), respectively. This work demonstrates that precise control of the fluorine functionalization in side chains of nonfused electron acceptors is an effective strategy for realizing highly efficient OSCs.

Hole‐Transporting Polymers Bearing Fine‐Tuning Side Chains via Ternary Copolymerization Strategy for High‐Performance Perovskite Solar Cells

AbstractThe binary electron donor–electron acceptor (D‐A) type conjugated polymers have proven to be efficient dopant‐free hole‐transporting materials (HTMs) for the n‐i‐p perovskite solar cells (PVSCs). However, D‐A type terpolymeric HTMs containing two D units are not exploited. Reserving the high‐planarity backbone of benzodithiophene (BDT)‐benzodithiophene‐4,8‐dione, D1‐A‐D2‐A type terpolymers PT‐Cz30, PT‐Cz50, and PT‐Cz70 are obtained by side‐chain engineering and ternary copolymerization strategy, in which BDT bearing the side chains of thiophene and carbazole serves as D1 and D2 units, respectively. PT‐Cz50 performs best due to the appropriate side‐chain ratio around 1:1. Meanwhile, a polymer blend HTM PA‐Cz50 is studied for comparison, in which two binary D‐A polymers PBDB‐T and PBDB‐Cz are blended with the molar ratio of 1:1. Containing similar side‐chain composition, terpolymer PT‐Cz50 presents superior hole transport properties over the polymer blend PA‐Cz50 and endows better device performances to the PVSCs with a promising power conversion efficiency of 22.53% and high device stability.

Ab-initio investigation of the fundamental properties of metals (X = Be, Mg, and Ca) encapsulated CsXO3 tin-based perovskite materials

Perovskite material are widely used in Solar cell device due to it promising properties and power conversion efficiencies (PCE). Most importantly, properties of the absorber layer such as the band gap, electronic, optical, chemical composition and the grain size of the perovskite absorbed layer are very sacrosanct when determining efficacy of the material for such application. Thus, in this work, the optical, structural stability, electronic, and mechanical properties of non-halide cubic perovskite CsXO3 (X = Mg, Be and Ca) was extensively studied using the first principles Density functional theory (DFT) approach. The structural, electronic and optoelectronic properties was evaluated using Quantum Espresso Simulation Package (QESP) with the plane wave self-consistent field (PWscf) code. The structural computation reveals that the Lattice constant as well as total energy of CsXO3 (X = Be, Mg and Ca) increases as the size of cation X (X = Be, Mg and Ca) increases such that CsCaO3 possess the highest energy. Contrary, the fermi energy decreases with increase in cationic size, however, CsCaO3 has the highest lattice constant value 4.3743 eV. Electronic properties investigation shows that the studied perovskite has a metallic property with no forbidden band. zero band gap materials can adsorb photon across the entire solar spectrum, including lower-energy photons which is an advantage over a non-zero band gap which can only absorb photon with energies higher than the band gap energy can be absorbed and converted into electricity. This enables more efficient utilization of sunlight and increased overall energy conversion. To ascertain the effect of atomic exchange and orbital contribution in the formation of electronic properties, partial density of state (PDOS) was calculated and the result reveal that electron transition occurs mostly from p-orbital oxygen atom having major contribution on the valence band to the d-orbital of Caesium atom having major contribution on the conduction band and X-cation having minor contribution. CsXO3 (X = Be, Mg and Ca) also shows fascinating optical properties and thus can be used to improve solar cell device.

Terminally Chlorinated and Thiophene-linked Acceptor-Donor-Acceptor Structured 3D Acceptors with Versatile Processability for High-efficiency Organic Solar Cells.

To exploit the potential of our newly developed three-dimensional (3D) dimerized acceptors, a series of chlorinated 3D acceptors (namely CH8-3/4/5) were reported by precisely tuning the position of chlorine (Cl) atom. The introduction of Cl atom in central unit affects the molecular conformation. Whereas, by replacing fluorinated terminal groups (CH8-3) with chlorinated terminal groups (CH8-4 and CH8-5), the red-shift absorption and enhanced crystallization are achieved. Benefiting from these, all devices received promising power conversion efficiencies (PCEs) over 16 % as well as decent thermal/photo-stabilities. Among them, PM6:CH8-4 based device yielded a best PCE of 17.58 %. Besides, the 3D merits with multi alkyl chains enable their versatile processability during the device preparation. Impressive PCEs of 17.27 % and 16.23 % could be achieved for non-halogen solvent processable devices prepared in glovebox and ambient, respectively. 2.88 cm2 modules also obtained PCEs over 13 % via spin-coating and blade-coating methods, respectively. These results are among the best performance of dimerized acceptors. The decent performance of CH8-4 on small-area devices, modules and non-halogen solvent-processed devices highlights the versatile processing capability of our 3D acceptors, as well as their potential applications in the future.