Efficient Solar Cells Research Articles

Achieving 19.72% Efficiency in Ternary Organic Solar Cells through Electrostatic Potential‐Driven Morphology Control

AbstractThe ternary strategy has proven effective in enhancing the performance of organic solar cells (OSCs), yet identifying the optimal third component remains a challenge due to the lack of theoretical frameworks for predicting its impact based on molecular structure. This study addresses this challenge by proposing quantitative parameters derived from molecular surface electrostatic potential (ESP) as criteria for selecting ternary components. The asymmetric acceptor BTP‐OS, which exhibits a lower total average ESP and larger molecular polarization index relative to the host acceptor, is introduced into the PM6:L8‐BO system. This incorporation led to weakened ESP‐induced intermolecular interactions and reduce miscibility with donor polymer, resulting in an optimized multi‐scale morphology of the ternary blend. Consequently, the ternary device achieved an efficiency of 19.72%, one of the highest values for PM6:L8‐BO‐based ternary devices, with enhanced exciton dissociation and charge collection, lower energy disorder, and minimized non‐radiative energy losses. Comparable efficiency improvements are also verified in PM6:BTP‐eC9 and D18:N3 systems, demonstrating the broad applicability of the proposed approach. This study not only provides a practical and effective principle for selecting ternary components but also establishes a broader framework for optimizing ternary OSCs, potentially advancing the development of more efficient OSCs across diverse material systems.

Mechanochemical synthesis and characterization of poly[(aniline-co-N-(4-sulfophenyl) aniline] nanofibers and its nanocomposite with titanium dioxide nanoparticles and study of their efficiency in hybrid solar cell

The advantages of polyaniline for application in new generation solar cells include its cost-effectiveness, environmentally friendly synthesis, remarkable stability, and the ability to modify the bandgap through the synthesis of its nanocomposites. But a challenge for its nanostructures is the limited solubility in non-toxic solvents, including water, which limits their processability in coating techniques. We overcame this challenge by synthesizing its copolymer with diphenylamine-4-sulfonate and its nanocomposite with titanium dioxide nanoparticles (TiO2NPs). So through a solid-state and template-free technique and using sodium diphenylamine-4-sulfonate, aniline hydrochloride salt, TiO2NPs, and FeCl3∙6 H2O as an oxidant, poly(N-(sulfophenyl)aniline) nanoflowers (PSANFLs), poly [(aniline-co-N-(4-sulfophenyl) aniline] nanofibers (PAPSANFs), poly(N-(sulfophenyl)aniline) nanofibers/titanium dioxide nanoparticles (PSANFs/TiO2NPs), and poly (aniline-co-N-(4-sulfophenyl)aniline nanofibers/titanium dioxide nanoparticles (PAPSANFs/TiO2NPs) were synthesized. Characterization of the synthesized samples was carried out through field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectra, ultraviolet-visible spectra (UV-Vis), cyclic voltammetry (CV), and elemental analysis (CHNS). The FE-SEM images clearly illustrate that the synthesized samples are of nanoscale dimensions. The band gap values of 2.23 eV for PSANFs/TiO2NPs and 1.96 eV for PAPSANFs/TiO2NPs nanocomposites were determined through electrochemical calculations based on cyclic voltammetry curves, showcasing the complementary properties of n and p semiconductors. Using doctor blade method to prepare films from synthesized materials and the architectural pattern of ITO│TiO2NPs│semiconductor sample│Al, all hybrid solar cells are fabricated. The I-V characteristics and power conversion efficiency (PCE) of the samples were examined and discussed. The PCE values for the four samples were found to be in the range of 0.20–0.82 %.

Two-dimensional Ruddlesden-Popper perovskite solar cells with an efficiency exceeding 19 % by inserting a self-assembled monolayer

Two-dimensional Ruddlesden-Popper (2DRP) phase perovskites have excellent long-term environmental and structure stability. However, the efficiency of 2DRP perovskite solar cells (PSCs) still lags seriously behind 3D counterparts due to the large exciton binding energy between the large-volume organic spacer and the inorganic plate compared to their 3D analogs. Here, a thin layer of self-assembled monolayer material (2-(3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz-Br) is employed between poly (3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) and β-guanidinopropanoic acid (β-GUA)-based perovskite film (β-GUA)2(FA)4Pb5I16 for efficient and stable 2DRP-based PSCs. The 2PACz-Br-based 2DRP perovskite films show superior crystallinity and quality compared with the control perovskite films. The defect density in 2PACz-Br-based perovskite films is reduced, and the non-radiative recombination is further suppressed. The experimental results show that introducing 2PACz-Br can effectively promote the matched energy levels between the perovskite thin film and the charge-carrier transport layer. Benefiting from the conducive collection and transmission of charge carriers, (β-GUA)2(FA)4Pb5I16 (n = 5)-based PSCs can realize an outstanding power conversion efficiency of 19.13 %, much higher than that of devices without 2PACz-Br modification (17.70 %). Moreover, 2PACz-Br-based 2DRP PSCs show better stability than the control devices. Our work paves the way to efficient and stable 2DRP-based PSCs by inserting a multifunctional self-assembled monolayer.

An Eco-Friendly Passivation Strategy of Resveratrol for Highly Efficient and Antioxidative Perovskite Solar Cells.

The stability of perovskite solar cells is closely related to the defects in perovskite crystals, and a large number of crystal defects are caused by the solution method. In this study, resveratrol (RES), a green natural antioxidant abundant in knotweed and grape leaves, is introduced into perovskite films to passivate the defect. RES achieves defect passivation by interacting with uncoordinated Pb2+ in perovskite films. The defect formation energy of VPb and PbI on the surface of perovskite thin films is increased by RES doping, as calculated by density functional theory. The results show that the quality of the perovskite film is significantly improved, and the energy level structure of the device is optimized, and the power conversion efficiency (PCE) of the device is increased from 21.62% to 23.44%. RES can hinder the degradation of perovskite structures by O2 - free radicals, and the device retained 88% of its initial PCE after over 1000 h in pure oxygen environment. The device retains 91% of the initial PCE after >1000 h at 25°C and 50 ± 5% relative humidity. This work provides an idea for the use of natural and environmentally friendly additives to improve the efficiency and stability of devices.

Harnessing SWCNT absorber based efficient CH3NH3PbI3 perovskite solar cells

This paper investigates the effect of incorporating a single-walled carbon nanotubes (SWCNTs) layer into the perovskite solar cell (PSC) structure as an effective technique to boost energy harvesting. The proposed PSC structure utilizes the SWCNTs layer underneath the CH3NH3PbI3 perovskite layer as an absorbing layer forming a novel design of (ITO/SnO2/CH3NH3PbI3/SWCNTs/NiOx/C) half tandem PSC structure. The suggested PSC structure is numerically analyzed using finite element method (FEM). The effects of varying thickness and doping concentration of the added layer and the material of rear electrode are investigated to maximize the power conversion efficiency (PCE) of the suggested PSC. Results of the 3D opto-electrical study and the energy bandgap analysis confirm that utilizing a 680 nm SWCNTs layer with doping concentration of 1.1 × 1020 cm-3 beneath a 150 nm perovskite layer enhances the PCE and short circuit current density (JSC) to 25.6%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$25.6\\%$$\\end{document} and 31.201mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$31.201 mA/{cm}^{2}$$\\end{document}, respectively due to the improving of the PSC absorption by 27.65%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$27.65\\%$$\\end{document}. Higher performance of the proposed PSC has been achieved by using gold (Au) electrode instead of carbon (C) one, causing total enhancement of PCE and JSC of 6.185%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6.185\\%$$\\end{document} and 9.18mA/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9.18\\;mA/cm^{2}$$\\end{document}, respectively over their values for (ITO/SnO2/CH3NH3PbI3/P3HT/NiOx/C) structure reported in previously published literature. The proposed design can be considered as an efficient alternative to the conventional PSC owing to its higher performance and reduced toxicity.

Study of Aluminium, Gallium and Gallium Boron as P-Type Dopants for New-Generation n+np+ Solar Cells

Silicon n-type n+np+ solar cells offer many advantages over conventional n+pp+ cells, including better resistance to light-induced degradation and higher conversion efficiency potential. However, the formation of the p+ emitter in n+np+ cells requires high diffusion temperatures and the use of alternative boron dopants is necessary to overcome the limitations of conventional processes. This study explored aluminium, gallium and gallium/boron co-doping as p-type dopants for the fabrication of thin (140 µm) n+np+ solar cells. The results showed that aluminium is not suitable for the formation of the p+ emitter due to its low solid solubility in silicon and its high segregation towards silicon oxide. Gallium required high diffusion temperatures and suffered from a degradation of the concentration profile in later stages of the manufacturing process, leading to poor performing solar cells. Gallium/boron co-doping has proved to be a promising alternative to boron. Thin n+np+ solar cells doped with GaB achieved a maximum conversion efficiency of 13.7%, slightly lower than that of boron-doped cells (14.9%). Optimisation of the GaB diffusion process and surface passivation could further improve the performance of these cells. This study demonstrates the potential of gallium/boron co-doping for the manufacture of new-generation thin n+np+ solar cells. Further research is needed to fully exploit the advantages of this technology and contribute to improving the efficiency and cost of silicon solar cells.

Exposing graphene oxide’s function in enhancing dye sensitized solar cell efficiency

This study aims to explore the potential for increasing the efficiency of the Dye sensitized solar cells through the incorporation of graphene oxide into the titanium dioxide matrix. The presence of defects was observed by Raman spectra. The structural properties and crystallite size of TiO2, GO, and GO/TiO2 composite were investigated using X-ray diffraction analysis, whereas the changes in morphology of graphene oxide and GO/TiO2 were assessed by Field Emission Scanning Electron Microscopy. The presence of functional groups were analyzed by Fourier Transform Infrared Spectroscopy. UV-Visible spectroscopy revealed a reduction in optical bandgap from 3.25 eV for TiO2 to 2.89 eV for GO/TiO2 and optical conductivity were observed increasing from 5.49 × 107 S/cm to 1.19 × 108 S/cm. The efficiency of the fabricated DSSCs was determined through I-V measurement, which showed that the addition of 0.2 wt% of graphene oxide in TiO2 significantly increased the short-circuit current from 0.38 milliampere to 0.75 milliampere, fill factor from 0.71 to 0.82, resulting in a substantial efficiency improvement from 3.99% to 9.11%.

Role of La2CuO4 as Buffer Layer for a Significant Improvement of the Performance of TiO2/Cu2O Based All‐Oxide Solar Cell: A SCAPS‐1D Numerical Analysis

AbstractCurrently, low‐bandgap Mott‐insulating materials are the most promising buffer layers (BLs) for solar power conversion efficiency, unlike organic‐halide or lead‐containing perovskite materials. They can reduce interfacial recombination by field effect passivation of heterojunctions while maintaining cost‐effectiveness and high thermal and electrical stability. Moreover, it is expected to obtain a high quantum efficiency due to multiple carrier generation caused by impact ionization from a single incident photon. This study uses the SCAPS‐1D simulator to estimate and improve the efficiency of Cu2O‐based solar cells using Mott insulator La2CuO4 (LCO) as a BL in both ideal and non‐ideal conditions. The simulations examine how BL thickness, carrier concentration, and defect density affect device performance. Also, different metal contact work functions and working temperatures are examined to improve cell performance. Considering all optimisation parameters in ideal conditions, Au/Cu2O/TiO2/Nb: STO solar cell structure without a BL has a PCE of 11.27%, while Au/Cu2O/LCO/TiO2/Nb: STO has 28.11%. By incorporating non‐idealities, the simulated solar cell can simulate actual conditions. The impact of each non‐ideality is studied in detail. These findings suggest that Mott insulating buffer materials have great potential for creating high‐efficiency photovoltaic (PV) devices, presenting a new avenue for research.

Surface Regulation via Carboxylate Polymer for Efficient and Stable CsPbI2Br Perovskite Solar Cells.

CsPbI2Br perovskite solar cell (PSC) is a promising candidate for high-efficiency single-junction and tandem solar cells. However, due to the numerous surface defects of the CsPbI2Br film and the mismatch of energy levels at the CsPbI2Br/charge transport layer interface, the power conversion efficiency (PCE) of CsPbI2Br PSC is still significantly lower than the theoretical limits. To alleviate those issues, in this work, a carboxylate-based p-type polymer, TTC-Cl, is employed to modify the surface of CsPbI2Br layer. TTC-Cl can interact with uncoordinated Pb2+, thereby mitigating surficial defects of CsPbI2Br film and reducing non-radiative recombination losses. Furthermore, TTC-Cl also improves the band properties of the CsPbI2Br thin film surface, rendering it more p-type, which facilitates hole transport. Consequently, the CsPbI2Br PSCs with TTC-Cl modification achieve a remarkable PCE of 17.81%, which is notably higher than that of counterpart without TTC-Cl (15.87%). Moreover, CsPbI2Br PSCs with TTC-Cl modification also exhibit better stability. This work highlights the importance of surface regulation via carboxylate polymer for further enhancing the performance of CsPbI2Br PSCs.

Self-Sacrificed Additive in Preparing PbI2 Film Enables the Oriented Growth of Perovskite Crystals for Improved Solar Cell Performance.

Due to the limitation of the diffusion kinetics of organic amine salts on the PbI2 layer in the two-step method, prepared perovskite particles are small in size, have many defects, and are randomly oriented, and the cell efficiency and stability are difficult to guarantee due to PbI2 residues. Here, we added a volatile additive, N,N,N',N'-tetramethylethylenediamine (TMEDA), to the PbI2 precursor solution and formed preaggregated atomic clusters with PbI2 through TMEDA, which reduced the Gibbs free energy of nucleation to obtain a porous PbI2 layer, and finally obtained a perovskite film with large particles, few defects, ideal crystal plane orientation, and no additive residues. The results show that the photoelectric conversion efficiency of the optimized device is increased by 1.68% (from 21.68% to 23.36%), and the unpackaged optimized device still maintains the maximum efficiency of 77% after being placed in the air for 1200 h. This study provides an effective way to fabricate efficient and stable perovskite solar cells by promoting the nucleation-induced crystallization orientation by volatile additives.

Mesoporous structured MoS2 as an electron transport layer for efficient and stable perovskite solar cells.

Mesoporous structured electron transport layers (ETLs) in perovskite solar cells (PSCs) have an increased surface contact with the perovskite layer, enabling effective charge separation and extraction, and high-efficiency devices. However, the most widely used ETL material in PSCs, TiO2, requires a sintering temperature of more than 500 °C and undergoes photocatalytic reaction under incident illumination that limits operational stability. Recent efforts have focused on finding alternative ETL materials, such as SnO2. Here we propose mesoporous MoS2 as an efficient and stable ETL material. The MoS2 interlayer increases the surface contact area with the adjacent perovskite layer, improving charge transfer dynamics between the two layers. In addition, the matching between the MoS2 and the perovskite lattices facilitates preferential growth of perovskite crystals with low residual strain, compared with TiO2. Using mesoporous structured MoS2 as ETL, we obtain PSCs with 25.7% (0.08 cm2, certified 25.4%) and 22.4% (1.00 cm2) efficiencies. Under continuous illumination, our cell remains stable for more than 2,000 h, demonstrating improved photostability with respect to TiO2.

Lattice Dynamics of Cu2ZnSn(S x ,Se1-x )4 Kesterite Thin-Film Solar Cells Studied by Nuclear Inelastic Scattering.

Phonons play a crucial role in thermalization and non-radiative recombination losses in semiconductors, impacting the power conversion efficiency of solar cells. To shed light on the lattice dynamics in Cu2ZnSn(S x ,Se1-x )4 (CZTSSe) thin-film solar cells and validate the extensive number of theoretical studies, we determine the 119Sn-partial phonon density of states (Sn-PDOS) by nuclear inelastic X-ray scattering. CZTSSe-based devices, one with near-stoichiometric and two with off-stoichiometric compositions, are investigated, and the results are correlated with the corresponding power conversion efficiencies (PCEs) of 3.2, 7.6, and 10.6%, respectively. Compared to the near-stoichiometric cell, the main Sn-PDOS peak of the off-stoichiometric cells broadens and slightly shifts to higher energy; this effect is correlated with the type and concentration of the characteristic defects in the studied samples. Furthermore, the Sn-PDOS of the 10.6% device is also obtained under operando (maximum power point) and open-circuit conditions. A comparison of the Sn-PDOS before and after the operando measurements suggests structural changes, likely due to the formation of metastable defects. In agreement with the theoretical studies, the Sn-PDOS of the CZTSSe absorber shows additional peaks compared to CZTSe attributed to coupling of Sn to the vibrations of Se and S atoms. This work paves the way for a further understanding of the lattice dynamics and subsequent enhancement of the PCEs of thin-film solar cells as well as other applied materials and devices containing elements that are Mössbauer-active and hence suitable for nuclear inelastic scattering.

Investigation of bismuth selenide’s structural stability and tunable bandgap under exposure to acoustic shock waves for solar cell and aerospace applications

Bismuth selenide is a promising semiconductor for optoelectronics and energy conversion, including solar cells and aerospace applications. However, it degrades at high temperatures, affecting stability. According to the previous literature, we can solve this problem and easily tune under high pressure, but no reports are available for response against acoustic shock waves. To explore this, commercially available Bi2Se3 was purchased and tested under acoustic shock wave exposure. Bi2Se3 was subjected to 100, 200, 300, and 400 acoustic shock waves with 0.59 MPa transient pressure at 520 K temperature and 1.5 Mach number. Before and after shock-loaded Bi2Se3 samples were characterized using XRD, Raman, UV-DRS, PL, and FE- SEM and EDX. Under acoustic shock waves, Bi2Se3 exhibits increased crystallite size and reduced strain rate, promoting good thermal stability. It also shows a smaller bandgap and enhanced PL intensity, which ensures efficient solar cell operation. As a result, the material demonstrates improved thermal insulation and durability, which are crucial for stability and protection in extreme conditions for aerospace applications. These improvements make Bi2Se3 more suitable for solar cell and aerospace applications.

Using Post‐Treatment Additives for Crystal Modulation and Interface Passivation Enables the Fabrication of Efficient and Stable Perovskite Solar Cells in Air

AbstractHigh‐performance perovskite solar cells (PSCs) fabricated in ambient air are considered inevitable for low‐cost commercial manufacturing. However, passivating perovskite film defects and controlling the crystallization process are critical for achieving high performance in PSCs. This study proposes using the novel 2D material MBene in green antisolvent to simultaneously modulate the crystallization and passivation defects of perovskites. MBene facilitates the passivation of uncoordinated Pb2+ ions, thereby enhancing the formation energy of vacancies within the perovskite film and adjusting the energy level structure. Moreover, MBene increases nucleation sites for perovskite, significantly extending crystal growth and improving film crystallinity, thereby reducing non‐radiative recombination. Consequently, champion devices treated with MBene achieve a power conversion efficiency (PCE) of 24.22% when fabricated in air, and exhibit superior humidity and long‐term stability. Furthermore, PSCs with added MBene exhibit significant long‐term stability under various environmental conditions, including humidity and heat. The study results lay a foundation for the development of MBene materials in photovoltaics, revealing their mechanism as a new type of 2D material in perovskites, and providing new insights for industrially producing efficient and stable solar cells.

Engineering Spacer Conjugation for Efficient and Stable 2D/3D Perovskite Solar Cells and Modules

Incorporating 2D perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky‐cation‐based 2D structures often exhibit poor charge transport and are prone to formation of charge‐extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with enhanced molecular conjugation. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency of up to 25.3% in a 0.16‐cm2 single cell and 21.0% in a 24.8‐cm2 module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA‐based devices retained over 90% of their initial efficiency after 2000 hours at 25 ℃ and 80% relative humidity, or 1000 hours at 85 ℃ and 85% humidity, or 3000 hours of operation under continuous 1‐Sun illumination at 40 ℃, showcasing their enhanced stability compared to previously reported 2D/3D PSCs.

Engineering Spacer Conjugation for Efficient and Stable 2D/3D Perovskite Solar Cells and Modules.

Incorporating 2D perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky-cation-based 2D structures often exhibit poor charge transport and are prone to formation of charge-extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with enhanced molecular conjugation. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency of up to 25.3% in a 0.16-cm2 single cell and 21.0% in a 24.8-cm2 module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA-based devices retained over 90% of their initial efficiency after 2000 hours at 25 ℃ and 80% relative humidity, or 1000 hours at 85 ℃ and 85% humidity, or 3000 hours of operation under continuous 1-Sun illumination at 40 ℃, showcasing their enhanced stability compared to previously reported 2D/3D PSCs.

3D/2D lead-free halide perovskite CsSnBr3/MoX (X = Se2, SSe, S2) heterostructures for high-efficiency solar cell: Interface engineering strategies and transition of band alignments

The rapid progress in the fabrication of van der Waals (vdW) heterostructures based on perovskite has significantly advanced the fields of optoelectronics and solar cells by integrating the exceptional properties of different materials. Overall, perovskite-based vdW heterostructures display unique functional characteristics due to their varied type-I, type-II, and type-III energy band configurations. However, it is a challenge to achieve flexible regulation of band edge alignment in heterostructures for different applications. Using first-principles density functional theory, we systematically study the electronic and optical properties of vdW heterostructures system consisting of three-dimensional lead-free all-inorganic halide perovskite materials CsSnBr3 and MoX (X = Se2, SSe, S2). The research results show that in the CsSnBr3/MoX vdW heterostructures, type I, II, and III transitions of band arrangements are achieved through interface engineering strategy to adapt to different applications. Meanwhile, by calculating the light absorption efficiency of the constructed 3D/2D vdW heterostructures, it was found that the interface effect enhances the optical absorption range and intensity of the perovskite-based heterostructures. The theoretically estimated power conversion efficiency (PCE) of the heterostructure thin-film solar cell reaches 21.4 %. The results of our research indicate that the controllable band alignment of CsSnBr3/MoX heterostructures has significant potential for future applications in optoelectronics.

Three-dimensional (3-D) fluoride molecular glue to improve the SnO2/perovskite interface for efficient perovskite solar cells.

Aiming at numerous defects at SnO2/perovskite interface and lattice mismatch in perovskite solar cells (PSCs), we design a kind of three-dimensional (3D) molecular glue (KBF4-TFMSA), which is derived from strong intramolecular hydrogen bonding interaction between potassium tetrafluoroborate (KBF4) and trifluoromethanesulfonamide (TFMSA). A remarkable efficiency of 25.8% with negligible hysteresis and a stabilized power output of 25.0% have been achieved, in addition, 24.57% certified efficiency of 1 cm2 device is also obtained. Further investigation reveals that this KBF4-TFMSA can interact with oxygen vacancies and under-coordinated Sn(IV) from the SnO2, in the meantime, FA+ (NH2-C=NH) and K+ cations can be well fixed by hydrogen bonding interaction between FA+ and BF4-, and electrostatic attraction between sulfonyl oxygen and K+ ions, respectively. Thereby, FAPbI3 crystal grain sizes are increased, interfacial defects are significantly reduced and carrier extraction/transport is facilitated, leading to better cell performance and excellent stabilities. Non-encapsulated devices can maintain 91% of their initial efficiency under maximum-power-point (MPP) tracking while continuous illumination (~100 mW cm-2) for 1000 h, and retain 91% of the initial efficiency after 1000 h "double 60" damp-heat stability testing (60°C and 60%RH (RH, relatively humidity)).

Fluorination or Not in Small Molecule Solar Cells: Achieving a Higher Efficiency with Halogen-free End Group.

Fluorination is an efficient strategy for improving organic solar cells (OSCs) efficiency, particularly by fluorinating the end group of emerging nonfullerene acceptors. Here, the fluorination effect was investigated by using small molecule donors with fluorine-free (SBz) and fluorinated (SBz-F) end groups, paired with the emerging nonfullerene acceptor Y6. Interestingly and unexpectedly, fluorination of the end group negatively affects OSCs efficiency, with fluorine-free SBz:Y6 OSCs achieving a higher power conversion efficiency (PCE) of 11.05% compared to the fluorine-containing SBz-F:Y6 blends (PCE = 9.61%). Analysis of space-charge limited currents reveals lower and unbalanced hole/electron mobility in SBz-F:Y6 compared to the SBz:Y6 blends. These findings are further supported by charge recombination dynamics and donor-acceptor miscibility analyses.

Enhanced charge carrier transport and defects mitigation of passivation layer for efficient perovskite solar cells

Surface passivation has been developed as an effective strategy to reduce trap-state density and suppress non-radiation recombination process in perovskite solar cells. However, passivation agents usually own poor conductivity and hold negative impact on the charge carrier transport in device. Here, we report a binary and synergistical post-treatment method by blending 4-tert-butyl-benzylammonium iodide with phenylpropylammonium iodide and spin-coating on perovskite surface to form passivation layer. The binary and synergistical post-treated films show enhanced crystallinity and improved molecular packing as well as better energy band alignment, benefiting for the hole extraction and transfer. Moreover, the surface defects are further passivated compared with unary passivation. Based on the strategy, a record-certified quasi-steady power conversion efficiency of 26.0% perovskite solar cells is achieved. The devices could maintain 81% of initial efficiency after 450 h maximum power point tracking.