High Fill Factor Research Articles

Interfacial engineering with a ferrocene derivative for air-stable inverted perovskite solar cells with high fill factor of 83.57 %

Perovskite solar cells have demonstrated exceptional photovoltaic performance, but stability remains a challenge due to insufficient interfaces. In this work, a UV-resistance ferrocene derivative, 1,1′-bis (diphenylphosphine) ferrocene (DPPF), is introduced between the electron transport layer and the perovskite, reducing defect density by interaction with undercoordinated Pb2+, suppressing non-radiative recombination of charge carriers, and enhancing electron extraction. Desirable interfacial properties and homogeneous perovskite grains are formed, resulting in a champion power conversion efficiency (PCE) of 20.82 % and a significantly improved fill factor of 83.57 %. Moreover, DPPF can optimize the interfaces, provide a brand-new morphology with exceptional air durability, cover the active layer to restrain water and oxygen intrusion, and suppress metal electrode corrosion. Resultant devices without encapsulation have remained above 80 % of their initial PCE for 1400 h under 25 °C air and 50–60 % relative humidity conditions.

Tailoring Cyano Substitutions on Quinoxaline‐based Small‐Molecule Acceptors Enabling Enhanced Molecular Packing for High‐Performance Organic Solar Cells

AbstractCyanation is a common chemical modification strategy to fine‐tune the energy levels and molecular packing of organic semiconductors, especially materials used in organic solar cells (OSCs). Generally, cyanation is used to modify the end groups of high‐performance small‐molecule acceptors (SMAs). However, the cyanation strategy has not been investigated on the central backbone of SMAs, which could introduce stronger intermolecular interaction and enhance the π–π stacking for rapid charge transport. This paper, for the first time, reports a new cyanation strategy on the central benzo‐quinoxaline core and synthesizes two novel A‐DA'D‐A type SMAs, named BQx‐CN and BQx‐2CN, with mono‐ and di‐cyanide groups, respectively. Through tailoring the number of CN groups, the BQx‐CN‐based OSC exhibits the best device performance of 18.8%, which is significantly higher than the non‐cyano BQx‐based one. The reason for the superior performance of BQx‐CN‐based devices can be attributed to the fine‐tuned energy level, stronger packing, and ideal phase segregation, which lead to superior exciton dissociation, faster charge transport, and suppressed recombination, therefore the highest fill factor (FF) and power conversion efficiencies (PCE). The research demonstrates the effectiveness of the cyanation strategy on the central core of SMAs for enhanced molecular packing and better performance of OSCs.

Bifunctional passivation by lewis-base molecules for efficient printable mesoscopic perovskite solar cells

Printable mesoscopic perovskite solar cells (PM-PSCs) possess notable merits in terms of cost-effectiveness, easy manufacturing, and large scale applications. Nevertheless, the absence of a hole transport layer contributes to the exacerbation of carrier recombination, and the defects between the perovskite and electron transport layer (ETL) interfaces significantly decrease the efficiency of the devices. In this study, a bifunctional surface passivation approach is proposed by applying a thioacetamide (TAA) surfactant on the mesoporous TiO2 interface. The results demonstrate that TAA molecules could interact with TiO2, thereby diminishing the oxygen vacancy defects. Additionally, the amino group and sulfur atoms in TAA molecules act as Lewis base to effectively passivate the uncoordinated Pb2+ in perovskite and improve the morphology of perovskite, and decrease the trap-state density of perovskite. The TAA passivation mechanism improves the alignment of energy levels between TiO2 and perovskite, facilitating electron transport and reducing carrier recombination. Consequently, the TAA-passivated device achieved a champion power conversion efficiency (PCE) of 17.86% with a high fill factor (FF) of 79.16% and an open-circuit voltage (VOC) of 0.971 V. This investigation presents a feasible strategy for interfacial passivation of the ETL to further improve the efficiency of PM-PSCs.

Calotropis-mediated biosynthesis of TiO2@SnO2/Ag nanocomposites for efficient perovskite photovoltaics

In this study, green SnO2@TiO2 nanocomposites were initially synthesized using an extract from the Calotropis plant as an electron transfer material for fabricating perovskite solar cells (PSCs). Further, plasmon impregnation (Ag-NPs) into the SnO2@TiO2 nanocomposites yielded nanocomposite (TiO2@SnO2/Ag) films. The effect of doping silver into the SnO2@TiO2 nanocomposites was investigated in detail to gain insights into how it influences the photovoltaic performance of the PSC. It resulted in enhanced quenching of photoluminescence compared to TiO2 and TiO2@SnO2 electron transport layers (ETLs), indicating faster charge extraction. PSCs utilizing the TiO2@SnO2/Ag ETL showed significantly improved performance with a power conversion efficiency of 22.2 %, a higher fill factor, and reduced hysteresis compared to cells with TiO2 and TiO2@SnO2 ETLs. The characterization of the nanocomposites revealed that the TiO2@SnO2/Ag ETL led to perovskite films with improved crystallinity, morphology, charge separation, and transfer properties. Electrochemical impedance spectroscopy confirmed the TiO2@SnO2/Ag ETL facilitated faster charge transfer and lower recombination at interfaces. Finally, the TiO2@SnO2/Ag ETL-based devices exhibited superior long-term stability in air, maintaining over 87 % of their initial efficiency. This work demonstrates that the incorporation of TiO2@SnO2/Ag nanocomposites is effective for developing high-performance and stable PSCs.

Enhancing the Efficiency and Stability of Tin-Lead Perovskite Solar Cells via Sodium Hydroxide Dedoping of PEDOT:PSS.

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) have gained interest as candidates for the bottom cell of all-perovskite tandem solar cells due to their broad absorption of the solar spectrum. A notable challenge arises from the prevalent use of the hole transport layer, PEDOT:PSS, known for its inherently high doping level. This high doping level can lead to interfacial recombination, imposing a significant limitation on efficiency. Herein, NaOH is used to dedope PEDOT:PSS, with the aim of enhancing the efficiency of Sn-Pb PSCs. Secondary ion mass spectrometer profiles indicate that sodium ions diffuse into the perovskite layer, improving its crystallinity and enlarging its grains. Comprehensive evaluations, including photoluminescence and nanosecond transient absorption spectroscopy, confirm that dedoping significantly reduces interfacial recombination, resulting in an open-circuit voltage as high as 0.90V. Additionally, dedoping PEDOT:PSS leads to increased shunt resistance and high fill factor up to 0.81. As a result of these improvements, the power conversion efficiency is enhanced from 19.7% to 22.6%. Utilizing NaOH to dedope PEDOT:PSS also transitions its nature from acidic to basic, enhancing stability and exhibiting less than a 7% power conversion efficiency loss after 1176h of storage in N2 atmosphere.

Defect passivation and carrier management via a multifunctional additive for efficient and stable wide-bandgap perovskite solar cells with high fill factor

Wide-bandgap (WBG) Methylammonium (MA)-free based perovskite solar cells (PSCs) have attracted widespread research interests due to their broad applicability in multijunction tandem. Nevertheless, the efficiency of WBG PSCs is restricted by unfulfilled potential in fill factor and large deficits in open-circuit voltage. The imbalanced carrier mobility not only plays a critical role in bulk non-radiative recombination loss but also hinders efficient charge collection for mixed I/Br WBG perovskites. Herein, we introduced additive named 2,8-Diiododibenzothiophene to overcome above issues. Inverted devices with enhanced photostability and a record fill factor of 85.7 % are demonstrated. Moreover, combining the semitransparent WBG PSCs with 1.25 eV-bandgap perovskite bottom cells, we realized 4-terminal tandem devices and a champion PCE of 28 % is achieved. The multifunctional additive strategy demonstrated here, will open new avenues for improving WBG PSCs’ 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%.

Flexible, Transparent, and Bifacial Perovskite Solar Cells and Modules Using the Wide-Band Gap FAPbBr3 Perovskite Absorber.

Perovskite solar cells (PSCs) offer impressive performance and flexibility, thanks to their simple, low-temperature deposition methods. Their band gap tunability allows for a wide range of applications, transitioning from opaque to transparent devices. This study introduces the first flexible, bifacial PSCs using the FAPbBr3 perovskite. We investigated the impact of optimizing electron and hole transport layers on the cells' bifaciality, transparency, and stability. PSCs achieved a maximum power conversion efficiency (PCE) of 6.8 and 18.7% under 1 sun and indoor light conditions (1200 lx), respectively, showing up to 98% bifaciality factor and an average visible transmittance (AVT) of 55%. Additionally, a P1-P2-P3 laser ablation scheme has been developed on the flexible poly(ethylene terephthalate) (PET) substrate for perovskite solar modules showing a PCE of 4.8% and high geometrical fill factor (97.8%). These findings highlight the potential of flexible, bifacial PSCs for diverse applications such as building-integrated photovoltaics (BIPV), agrivoltaics, automotive technology, wearable sensors, and Internet of things (IoT).

Mixed cations tin-germanium perovskite: A promising approach for enhanced solar cell applications

Significant progress has been made over the years to improve the stability and efficiency of rapidly evolving tin-based perovskite solar cells (PSCs). One powerful approach to enhance the performance of these PSCs is through compositional engineering techniques, specifically by incorporating a mixed cation system at the A-site and B-site structure of the tin perovskite. These approaches will pave the way for unlocking the full potential of tin-based PSCs. Therefore, in this study, a theoretical investigation of mixed A-cations (FA, MA, EA, Cs) with a tin-germanium-based PSC was presented. The crystal structure distortion and optoelectronic properties were estimated. SCAPS 1-D simulations were employed to predict the photovoltaic performance of the optimized tin-germanium material using different electron transport layers (ETLs), hole transport layers (HTLs), active layer thicknesses, and cell temperatures. Our findings reveal that EA0.5Cs0.5Sn0.5Ge0.5I3 has a nearly cubic structure (t = 0.99) and a theoretical bandgap within the maximum Shockley-Queisser limit (1.34 eV). The overall cell performance is also improved by optimizing the perovskite layer thickness to 1200 nm, and it exhibits remarkable stability as the temperature increases. The short-circuit current density (Jsc) remains consistent around 33.7 mA/cm2, and the open-circuit voltage (Voc) is well-maintained above 1 V by utilizing FTO as the conductive layer, ZnO as the ETL, Cu2O as the HTL, and Au as the metal back contact. This configuration also achieves a high fill factor ranging from 87 % to 88 %, with the highest power conversion efficiency (PCE) of 31.49 % at 293 K. This research contributes to the advancement of tin-germanium perovskite materials for a wide range of optoelectronic applications.

Enhanced fill factor and stability of perovskite solar cells with a multifunctional additive of starch-iodine complex

The efficiency and stability of perovskite solar cells (PSCs) can be greatly affected by various factors such as passivating the perovskite film, oxidizing the hole-transport material of 2,2′,7,7′-tetras(N,N-p-methoxyaniline)-9,9′-spirodifluorene (Spiro-OMeTAD), and inhibiting the iodide migration. Here we introduce a multifunctional starch-iodine complex in the perovskite film to enhance the fill factor and stability of PSCs. Results demonstrate that the starch-iodine complex from the perovskite film can release iodine molecules to gently oxidize the Spiro-OMeTAD, which can significantly increase the PSC's fill factor. Moreover, the remaining starch can effectively passivate the perovskite film to obviously improve the PSC's long-term stability. Furthermore, the starch-iodine complex can absorb and store the iodide ions to generate a starch-triiodide complex, which can release iodide ions to promote iodide defect self-healing and suppress iodide migration in the perovskite films, resulting in a further enhancement of the PSC's long-term stability. As a result, the PSC based on the starch-iodine complex obtains a superior cell efficiency of 22.60% with a high fill factor of 79.54%, and keeps 91.12% of its original efficiency after 1500 h.

Removable Additive Assists Blade‐Coated Large‐Area Organic Solar Cell Modules Fabricated with Non‐Halogenated Solvents Achieving Efficiency Over 16%

AbstractThe critical step in commercializing organic solar cells (OSCs) involves achieving high‐performance modules through environmentally friendly solvents. The incorporation of solid additives, recognized as an effective method for modulating the morphology of active layers through layer‐by‐layer (LBL) deposition, plays a significant role. Here, a novel volatile solid additive is introduced individually into the non‐halogenated solution of donor PM6 as a morphology‐modulating agent. The additive induces conformational and crystalline orientation change of PM6, resulting in enhanced and balanced charge transport in the active layer. With a focus on exciton dynamics, the optimized active layer inhibits the formation of low‐energy triplet states. It facilitates strong reverse hole transfer processes, leading to more efficient exciton dissociation. The final small‐area LBL blade‐coated OSCs fabricated under ambient conditions achieve a power conversion efficiency (PCE) of 18.42%. Furthermore, a large‐area module with an area of 28.82 cm2 is manufactured, achieving a PCE of 16.04% with a high geometric fill factor of 93.8%. This highlights the effective modulation of the active layer through the use of solid additives and provides a successful strategy for fabricating high‐performance OSC modules with non‐halogenated solvents.

Achieving High Fill Factor in Organic Photovoltaic Cells by Tuning Molecular Electrostatic Potential Fluctuation.

In the field of organic photovoltaics (OPVs), significant progress has been made in tailoring molecular structures to enhance the open-circuit voltage and the short-circuit current density. However, there remains a crucial gap in the development of coordinated material design strategies focused on improving the fill factor (FF). Here, we introduce a molecular design strategy that incorporates electrostatic potential fluctuation to design organic photovoltaic materials. By reducing the fluctuation amplitude of IT-4F, we synthesized a new acceptor named ITOC6-4F. When using PBQx-TF as a donor, the ITOC6-4F-based cell shows a markedly low recombination rate constant of 0.66×10-14 cm3 s-1 and demonstrates an outstanding FF of 0.816, both of which are new records for binary OPV cells. Also, we find that a small fluctuation amplitude could decrease the energetic disorder of OPV cells, reducing energy loss. Finally, the ITOC6-4F-based cell creates the highest efficiency of 16.0 % among medium-gap OPV cells. Our work holds a vital implication for guiding the design of high-performance OPV materials.

Achieving High Fill Factor in Organic Photovoltaic Cells by Tuning Molecular Electrostatic Potential Fluctuation

AbstractIn the field of organic photovoltaics (OPVs), significant progress has been made in tailoring molecular structures to enhance the open‐circuit voltage and the short‐circuit current density. However, there remains a crucial gap in the development of coordinated material design strategies focused on improving the fill factor (FF). Here, we introduce a molecular design strategy that incorporates electrostatic potential fluctuation to design organic photovoltaic materials. By reducing the fluctuation amplitude of IT‐4F, we synthesized a new acceptor named ITOC6‐4F. When using PBQx‐TF as a donor, the ITOC6‐4F‐based cell shows a markedly low recombination rate constant of 0.66×10−14 cm3 s−1 and demonstrates an outstanding FF of 0.816, both of which are new records for binary OPV cells. Also, we find that a small fluctuation amplitude could decrease the energetic disorder of OPV cells, reducing energy loss. Finally, the ITOC6‐4F‐based cell creates the highest efficiency of 16.0 % among medium‐gap OPV cells. Our work holds a vital implication for guiding the design of high‐performance OPV materials.

High‐Performance Perovskite Solar Cells with Zwitterion‐Capped‐ZnO Quantum Dots as Electron Transport Layer and NH4X (X = F, Cl, Br) Assisted Interfacial Engineering

The systematic advances in the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs) have been driven by the developments of perovskite materials, electron transport layer (ETL) materials, and interfacial passivation between the relevant layers. While zinc oxide (ZnO) is a promising ETL in thin film photovoltaics, it is still highly desirable to develop novel synthetic methods that allow both fine‐tuning the versatility of ZnO nanomaterials and improving the ZnO/perovskite interface. Among various inorganic and organic additives, zwitterions have been effectively utilized to passivate the perovskite films. In this vein, we develop novel, well‐characterized betaine‐coated ZnO QDs and use them as an ETL in the planar n‐i‐p PSC architecture, combining the ZnO QDs‐based ETL with the ZnO/perovskite interface passivation by a series of ammonium halides (NH4X, where X = F, Cl, Br). The champion device with the NH4F passivation achieves one of the highest performances reported for ZnO‐based PSCs, exhibiting a maximum PCE of ~22% with a high fill factor of 80.3% and competitive stability, retaining ~78% of its initial PCE under 1 Sun illumination with maximum power tracking for 250 h.

Investigating the impact of end-capped acceptor alterations to dimethyl fluorene-based hole transporting material for perovskite solar cells

Hole-transporting materials (HTMs) could boost the proficiency of third generation-perovskite solar cells since they have ultrafast charge mobility that improves optoelectronic and photovoltaic attributes. Five new H-shaped molecules were sketched using thiophene bridged, end-capped acceptor alteration on a dimethyl fluorene core-based molecule. Planarity measurements, absorption spectra, frontier molecular orbitals (FMOs), excitation energy (Ex), density of states (DOS), molecular electrostatic potentials (MEPs), transition density matrix (TDM), exciton binding energy, interaction coefficient, hole-electron overlap, open circuit voltage, fill factor, and power conversion efficiency were analyzed via DFT/MPW1P9W1/6-31G (d,p) for evaluating performance of perovskite solar cells. All newly sketched molecules with an A-π-D-π-A skeleton exhibited outstanding optoelectronic properties, including broader absorbance (563–740 nm) in chlorobenzene, indicating better solution processing. Lower band gaps (2.08–2.72 eV) than reference (3.78 eV) indicated efficient electron density transfer. Increased open-circuit voltage (1.55–2.02 eV) along with lower reorganization energies of the electron (0.043249–0.122527 eV) and hole (0.108105–0.148322 eV) lead to effective charge transport capabilities. Higher dipole moments indicated suitable film fabrication. A higher fill factor (0.9166–0.9325) and power conversion efficiency (34.31–45.49 %) led to an improved performance. Concisely, all the newly sketched molecules showed redshifted absorbance, narrower band gaps, deeper HOMO energies, improved charge transfer, higher softness, and smaller hardness values when compared to ZR, which confirms their superiority as future dopant-free HTM for PSCs.

Fabrication of a piezoelectric micromachined ultrasonic transducer (PMUT) with dual heterogeneous piezoelectric thin film stacking

In this study, a piezoelectric micromachined ultrasonic transducer (pMUT) was developed using dual heterogeneous piezoelectric thin films stacked on top of each other. One piezoelectric layer is specialized for the actuation, while the other is specialized for the reception of the ultrasonic waves. This combined use of two materials promises to realize a pMUT transceiver array with an excellent transmitting and receiving performance and a high fill factor. Taking fabrication feasibility into consideration, AlN/Pb(Mg1/3, Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(Zr, Ti)O3 (PZT)/AlN pMUTs were selected as two candidates for prototyping as the dual-layer pMUTs. The driving tests were performed by actuation of each piezoelectric layer and a resonance frequencies around 265 kHz and 203 kHz were confirmed for AlN/PMN-PT and PZT/AlN pMUT, respectively. The diaphragm of AlN/PMN-PT pMUT has a displacement sensitivity of 3538 nm V−1 and 306 nm V−1 when actuating PMN-PT layer and AlN layer at resonance frequency, respectively. While the diaphragm of PZT/AlN pMUT has a displacement sensitivity of 1036 nm V−1 and 744 nm V−1 when actuating the PZT layer and the AlN layer at the resonance frequency, respectively.

The Effect of Comb Cell Size on the Development of Apis mellifera Drones.

The growth and development of honeybees are influenced by many factors, one of which is the cell size of the brood comb. Larger worker bees can be obtained by being raised in bigger cells. However, whether cell size has the same effect on drone development is still unknown. Here, using 3D-printed foundations, we observed the development of drones kept in comb cells of different sizes from the late larval stage through eclosion. The results showed that drones in larger cell-size combs had heavier body weights, longer body lengths, and larger head widths, thorax widths, and abdomen widths compared to those in smaller cell-size combs. Furthermore, regardless of developmental stages, the drones' body weights increased linearly with the comb's cell size. However, the other morphological changes of drones in different developmental stages were out of proportion to the cell-size changes, resulting in smaller cells with a higher fill factor (thorax width/cell width). Our findings confirm that comb cell size affects the development of honeybees; drones become bigger when raised in large cells.

Pizza Oven Processing of Organohalide Perovskites (POPOP): A Simple, Versatile and Efficient Vapor Deposition Method

AbstractHybrid vapor deposition is one of the most appealing processes for perovskite photovoltaics fabrication, thanks to its versatile nature. By using sequentially different vapor deposition processes tailored to the inorganic and organic perovskite precursors' peculiarities, this type of process gives access to the full potential of vapor deposition. While vapor deposition of metal halides is well understood and mastered, vapor deposition of organohalide species is much more delicate (degradation of vapors, high vapor pressure, setup‐specific constraints). Here, a novel close space sublimation system is reported and in‐depth insights on the conversion into perovskite of a metal halide template are provided. In this evolution of the process, the substrate coated with metal halide template and the organohalide source are loaded together in a dedicated holder, then transferred into a vacuum chamber on a heating element already at temperature setpoint. The system enables a simple, fast, low‐cost, and easy‐to‐reproduce organohalide vapor deposition process. The formation of the perovskite in situ and identification different conversion regimes are studied. Furthermore, the influence of the chemical environment and chamber design on the process are discussed. Compositional tuning and additive engineering in the process are processed and fabricate proof of concept photovoltaic devices reaching high fill factors of 80% and 17% power conversion efficiency for a bandgap of 1.63 eV.

SWGO: a wide-field of view gamma-ray observatory in the southern hemisphere

Abstract The recent LHAASO and HAWC results opened the way to the search of gamma ray sources emitting at energies above 100 TeV. Both detectors are in the northern hemisphere; the need for such an observatory in the southern hemisphere is therefore clear. The goal of the SWGO collaboration is the construction of a wide field of view, high duty cycle observatory to explore the Southern hemisphere sky searching for gamma ray sources at energies above 100 GeV. Such an array will detect extensive air showers particles and must be able to select the photon originated showers from the background of the hadronic ones. The experiment must be located in a site at latitude between 10° and 30° degrees south and at an altitude above 4400 m a.s.l. The baseline detection technique chosen by the collaboration is Water Cherenkov Detectors. The array will have a central region with high fill factor (>60%) and a large (about 1 km2) outer region with a much lower fill factor (around 4–5%).

Intramolecular charge transfer character of D-π-A chromophores with modulating the subunits sequence of π-bridge

Two D-B-A compounds (TRD and TTRD) were designed with the different bridges (B1 and B2) consisting of T and TT moieties. They were synthesized and investigated by UV–Vis spectra, steady state emission spectra, X-ray diffraction, electrochemical measurement, the photovoltaic performances and theoretical calculation. The large Stokes shift suggested the formation of an intramolecular charge transfer (ICT) state in the excited state. TTRD based device showed high short-circuit current density (JSC) and fill factor (FF). It was essential to understanding the underlying mechanism caused by the subtle structural difference of the two spacers. The results showed that the B2 bridge extending the electron increment region has shown a significant improvement for excitation delocalization, which played a crucial role in improving effective dissociation of the ICT excitons, leading to the increase of photogenerated charge carriers.