Conventional phosphonic acid-based SAMs, exemplified by [4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid (MeO-4PACz), readily aggregate, leading to non-uniform buried-interface coverage and constrained device output. Here, we engineer co-assembled SAMs (Co-SAMs) by co-assembling MeO-4PACz with trimethoxysilane-anchored terminal siloxanes-epoxy (GOPS), thiol (TMSPT) and isocyanate (IPTMS)-to homogenize the NiOx/perovskite contact. The resulting Co-SAMs form denser and more uniform interfacial layers on NiOx, boosting the open-circuit voltage (V oc) and fill factor (FF) of 1.68 eV wide-bandgap perovskite solar cells, with IPTMS-based Co-SAMs delivering the largest improvement. Performance correlates with a distinct evolution of siloxane-mediated intermolecular interactions. We demonstrate that the evolution of intermolecular interactions from physical blending (MeO4-GOPS) and specific hydrogen bonding (MeO4-TMSPT) to covalent bridging (MeO4-IPTMS) significantly enhances interfacial quality. Specifically, the phosphonate-carbamate covalent bridge formed in MeO4-IPTMS most effectively suppresses aggregation and delivers synergistic defect passivation. Leveraging this strategy, monolithic perovskite/silicon tandem cells deliver a champion power conversion efficiency (PCE) of 33.74% (certified 33.37%). Furthermore, the devices exhibit exceptional stability, showing negligible degradation after 4000 h of dark storage and retaining 87.12% of their initial PCE after 1000 h of maximum power point tracking (MPPT) under continuous one-sun illumination, highlighting the potential of this interfacial strategy for highly stable tandem photovoltaics.

Self-assembled monolayers (SAMs) as hole-selective contacts (HSCs) have driven efficiency improvements in inverted perovskite solar cells (PSCs) in recent years. However, their non-uniform coverage on metal oxide electrodes and stress-induced molecular desorption lead to interfacial recombination and compromise device operating stability. Here, we develop a metal-ion-linked self-assembled molecular layer (MiLSAM) as a robust HSC. Through a sequential assembly process, a molecular network with high-valent metal ions as crosslinking nodes is formed, enabling homogeneous substrate coverage and enhanced stability against surface restructuring. Inverted PSCs employing MiLSAM achieved a power conversion efficiency (PCE) of 26.71% (certified 26.46%), while 1 cm2 devices delivered a PCE of 25.75%. Encapsulated devices retained 91% of their initial PCE after 2,000 h near the International Summit on Organic Photovoltaic Stability (ISOS)-D-3 (85°C, 85% RH) and 90% after 1,000 h of maximum power point tracking near ISOS-L-3 (85°C, 50% RH), demonstrating simultaneous gains in efficiency and operational stability.

Hydrogenated nanocrystalline silicon (nc-Si:H) is usually utilized to prepare carrier-selective contacts for silicon heterojunction (SHJ) solar cells to mitigate the negative parasitic optical absorption. Nevertheless, it was found here that for the SHJ solar cell based on an n-type crystalline silicon (c-Si(n)) wafer with the p-type boron-doped nc-Si:H(p) as the emitter, the solar cell fill factor (FF) was limited by the contact performance of the nc-Si:H(p)/indium tin oxide (ITO) interface due to the induced disorder defects in the interface vicinity regions by the lattice mismatch between the nc-Si:H(p) and ITO crystallites. A strategy to improve the nc-Si:H(p)/ITO contact was proposed by inserting an ultrathin (similar to 2 nm) p-type hydrogenated amorphous silicon (a-Si:H(p)) buffer layer (p(b)) onto the nc-Si:H(p)/ITO interface. The inserted amorphous buffer plays well to facilitate the relaxation of the lattice mismatch stress on the interface and thus avoids the generation of disorder defects. Its Fermi energy level (E-f), lower than that of nc-Si:H(p), also promotes the carrier tunneling with ITO. Further, the hydrogen dilution ratio (R-H), boron doping (R-B2H6), and thickness of the p(b) layer were optimized. Comparing to the solar cell without the p(b) layer, the FF and conversion efficiency of the solar cell with the optimized p(b) layer achieved a relative increase of 0.37% and 0.56%, respectively. Since crystalline/crystalline heterojunctions like the nc-Si:H(p)/ITO scheme are utilized in a variety of photonic devices, such an interface modification strategy of inserting an amorphous buffer can be of great importance in the photonics field.

In the field of solar cell technology, the conversion efficiency of silicon heterojunction (SHJ) solar cells has reached 27.08%. Meanwhile, perovskite/SHJ tandem solar cells based on this structure have achieved an efficiency of 34.85%, exceeding the theoretical limit of 33.7% for single-junction devices. In the industry transitions from single-junction to tandem configurations, SHJ cells, due to their unique structure and low-temperature fabrication process, exhibit superior compatibility with perovskite layers. This makes SHJ technology play a critical role in the development of perovskite/tandem solar cells. The application of high-performance silver-coated copper (Cu@Ag) paste to electrode metallization provides a feasible method to reduce the costs and improve the performance of SHJ cells. However, the micron-scale particle size of Cu@Ag powder (typically several micrometers) limits the packing density of the electrode layer. To address this, nano-silver powder (about 100 nm) is commonly used as an additive, which enhances both the packing density of the powder and the electrical conductivity through nano-effects. Although many studies focus on isolated aspects such as paste conductivity, a systematic evaluation covering contact resistivity, printed and cured electrode morphology, overall cell performance, and long-term stability remains scarce. Potential adverse effects of nano-silver addition have also been overlooked. Therefore, a thorough investigation on the role of nano-silver in low-temperature Cu@Ag pastes is necessary. Highly conductive low-temperature curing pastes generally use binary or ternary composite powders with well-separated particle sizes to achieve high packing density according to the dense packing theory. In this work, we systematically adjust the proportions of three conductive powders: micro-sized Cu@Ag (3-5 mu m), sub-micron silver (500 nm), and nano-silver (100 nm), to study the effects of nano-silver on key properties of Cu@Ag paste. These include curing temperature and sintering behavior, microstructure of cured electrodes, interface structure between electrodes and the silicon wafer, electrical resistivity, and the overall conversion efficiency of SHJ solar cells. The aim is to clarify the underlying mechanisms and optimize the nano-silver content. This research reveals several significant influences of nano-silver addition on Cu@Ag paste properties. 1) It markedly reduces the resistivity of the cured electrode. Compared with sub-micron silver, nano-silver facilitates improved lateral conductivity at lower sintering temperatures. 2) It introduces additional pores at the contact interface with the silicon wafer, thereby increasing contact resistivity. A thickened organic layer at the interface also forms, which reduces the open-circuit voltage of the cell. 3) It enhances paste thixotropy, resulting in narrower printed electrode lines to reduce shading loss and increase short-circuit current density. At the same time, it raises electrode height and cross-sectional area, which helps improve the fill factor. 4) When the nano-silver content is controlled at 15%, the efficiency of SHJ cells is comparable or close to that of reference cells with pure silver electrodes, mainly due to the improvement of fill factor and short-circuit current density. In summary, an optimized amount of nano-silver powder (e.g., 15%) can simultaneously enhance electrode conductivity, printability, and opto-electrical performance, resulting in SHJ cells with efficiency comparable to those using pure silver electrodes. This demonstrates the potential of Cu@Ag pastes as a cost-effective alternative without compromising performance. Future studies should focus on the long-term reliability of such paste and its scalability, which will support the mass adoption of this technology in various tandem solar cells.

Despite already high expectations from the sustained progress of photovoltaics over multiple decades, the most recent decade has seen unexpectedly rapid growth and technological evolution. Annual solar installations increased to 600 GW/year in 2024, a massive 30%/year compounded growth from 45 GW installed in 2014. From 2025, solar will generate more electricity globally than either nuclear or wind, with rapidly escalating margins. Even more impressive is the decadal evolution in the sophistication of the dominant silicon cell technology. After 40 years of stability, with a rugged, reliable approach developed in the 1970s, technology is now evolving on a sub-decadal cycle toward ever-increasing energy-conversion efficiency, with five technologies now accounting for most fielded products. This paper gives an overview of past research and discusses the strengths and weaknesses of these competing technologies, along with what the future might look like for silicon photovoltaics, including where silicon-based tandem stacks might fit into the picture.

The construction of a high-quality interface with excellent surface passivation and carrier transport is critical to the device performance of solar cells. Low-dimensional perovskite structures are widely explored for surface passivation due to their effective suppression of interfacial defects and enhanced environmental stability. While terminal molecules for constructing low-dimensional structures provide excellent passivation, they can introduce potential barriers for charge transport if the energy levels are not well-aligned. Herein, a tryptamine molecule is explored as the terminal molecule for the construction of a low-dimensional structure for passivating the buried interface of perovskite solar cells. Based on the inclusion of nitrogen atoms in the aromatic heterocyclic structure, the terminal molecule shows an uplifted HOMO level that aligns well with the perovskite skeleton, giving rise to enhanced orbit coupling. Therefore, this low-dimensional structure enables excellent surface passivation and interfacial carrier transport simultaneously, generating an outstanding open-circuit voltage (VOC) up to 1.266 V and an efficiency of 23.53% for single-junction wide-bandgap (1.68 eV) perovskite solar cells. This improvement enables the fabrication of the perovskite/silicon tandem solar cell with an efficiency of 33.22% (32.88% assessed by a third party) and a VOC of 1.987 V. Moreover, the fast carrier transport at the interface suppressed the halide phase segregation, bringing much enhanced operation stability.

A multifunctional additive Na[B(C 2 O 4 )F 2 ] regulates crystallization and band alignment in wide-bandgap perovskites. Tandem cells achieve 34.28% certified efficiency (1.001 cm 2 ) and retain >93% after 2000 h at 65 °C.

Flexible two-terminal (2 T) monolithic perovskite/silicon tandem solar cell combines high-performance perovskite absorber with a thin crystalline silicon bottom cell, delivering high power conversion efficiency and mechanical flexibility. This architecture also offers competitive power-per-weight, making it well-suited for weightsensitive applications. This review assesses flexible 2 T perovskite/silicon tandems, with attention to performance metrics, mechanical stability, and approaches for structural integrity, including thin silicon substrate reinforcement, additive engineering for wide-bandgap perovskites, and residual stress management. Power-perweight considerations are addressed at both cell and module levels. Major challenges are also examined, including optical management, perovskite uniformity on textured thin silicon, and tandem-compatible metallization and interconnection. Finally, other concerns and prospects are discussed, including environmental durability, application-specific challenges, and life-cycle economic and sustainability analysis.

Against the backdrop of persistently high silver price, silver paste further intensifies cost pressure on crystalline silicon and tandem solar cells. There is an urgent need to develop low-silver or silver-free conductive pastes with reduced cost to achieve the dual objectives of cost reduction and efficiency enhancement in solar cells. Among the available strategies, replacing silver powder with silver-coated copper powder currently represents one of the most effective cost-reduction approaches for conductive pastes. Silver-coated copper paste not only delivers electrical performance comparable to that of conventional silver paste but also substantially lowers material cost due to its reduced silver content. Moreover, it demonstrates superior resistance to continuous oxidation and enhanced long-term reliability. Consequently, it has emerged as a key material for the metallization of both crystalline silicon and tandem solar cells. Silver-coated copper powder typically comprises spherical microparticles with the particle size ranging from 1.0 to 7.0 mu m and exhibits high packing porosity. Therefore, achieving optimal conductivity requires the incorporation of submicron silver powder to improve particle packing density and nano-silver powder to facilitate low-temperature sintering. However, driven by the industry-wide trend toward silver reduction, identifying viable alternatives to nano-silver powder is critically important for further cost-effective optimization of paste performance. Conductive nano-oxide powders possess high surface energy, high electrical conductivity, high melting and boiling points, and low shrinkage, rendering them promising candidates to replace the nano-silver powder. Nano-antimony tin oxide (ATO) powder, as a representative n-type semiconductor material, shares the same semiconductor type as the window layer in SHJ (silicon heterojunction) or tandem solar cells. It readily forms ohmic contacts when interfaced with either silver-coated copper powder or silver powder and exhibits low resistivity. Compared with costly nano-silver powder, its cost-effectiveness is particularly pronounced. This study aims to enhance the sintering behavior and conductivity of low-temperature silver-coated copper paste through the addition of high-surface-energy nano-ATO powder. Using SHJ solar cells as the test platform, the application effects and underlying mechanisms are systematically investigated. The impact of nano-ATO is evaluated with respect to the paste's thermodynamic properties, rheological behavior, electrical performance, and corresponding solar cell performance. The main findings are as follows: 1) When the ATO content is <= 1.5%, it effectively lowers the volatilization temperature of solvents during the curing process, minimizes solvent residue, and thereby promotes both powder sintering and resin curing. 2) As the ATO content increases, key rheological properties of the paste-including thixotropy, yield stress, and elastic modulus are enhanced. The static paste structure is reinforced, which helps suppress sagging and enables the printing of narrower, more stable line widths. 3) The bulk resistivity of the paste initially decreases and subsequently increases with rising ATO content, whereas the contact resistivity between the electrode and the substrate continues to decline as ATO content increases. 4) ATO powder reduces the accumulation of organic resin at the contact interface, thereby improving the open-circuit voltage. Additionally, it facilitates the formation of finer grid lines, which enhances the short-circuit current. The series resistance of the solar cell first decreases and then increases with increasing ATO content. Driven by the synergistic effects of these factors, the efficiency of the SHJ solar cell peaks at an ATO addition of 1% (mass fraction), achieving a relative improvement of 0.485% compared with that of the conventional solar cell prepared with silver paste. This demonstrates that an optimal amount of nano-ATO powder can effectively enhance the overall conductivity of the paste, thereby significantly improving the comprehensive performance of the solar cell.

Efficient solar steam generation requires synergistic light absorption and water supply. We coat TiN nanoparticles, synthesized by solid-phase ammonolysis, onto a hydrophilic cotton pad. The TiN offers broadband plasmonic absorption, while the cotton enables rapid capillary water transport. Under one sun, the device achieves an evaporation rate of 3.05 kg·m−2·h−1 and a solar-to-vapor efficiency of 96.97%, with stable performance over 48 h. This work provides a cost-effective, synergistic design strategy for solar water purification.

Improving surface passivation is a critical strategy for enhancing the efficiency of crystalline silicon (c-Si) solar cells. Here, we proposed a strategy to passivate the n-type c-Si wafers by depositing nano a-SiOx:H/AlOx:H bilayer stack without any post-deposition annealing (PDA). The optimized 6 nm a-SiOx:H/12 nm AlOx:H bilayer stack yields a maximum effective minority carrier lifetime (tau eff) of about 5 ms by providing a fixed negative charge density (Qf) of-6.9 & times; 10(12) cm-2 and reducing the interface defect density (Dit) to 6.1 & times; 10(10) eV-1 center dot cm-2 to achieve excellent chemical passivation and strong field-effect passivation simultaneously. According to the results of characterizations, the suppression of Al-OH species and the formation of a nearly stoichiometric Al-O network are significant for realizing high passivation quality in the a-SiOx:H/AlOx:H bilayer stacks. Moreover, it has been proved that compared to a-Si:H, a-SiOx:H prepared with appropriate gas flow of [CO2]/[SiH4] (R-CO2) during the deposition exhibits better passivation performance for the stack structure. Overall, the synergistic effect of high negative Qf from AlOx:H nanolayer and low Ditfrom a-SiOx:H nanolayer with appropriate oxygen content enables excellent surface passivation without PDA, providing a facile and industry-compatible passivation scheme for high-efficiency c-Si based solar cells.

Titanium carbide (TiCx) thin films were fabricated by radio frequency magnetron sputtering to study their photovoltaic properties. The dense crystalline TiCx thin films with bandgap and work function of 2.9 eV and 4.3 eV were prepared. The energy band distribution of heterojunction solar cells with different carrier concentrations and work functions of transparent conductive films was simulated by AFORS-HET software. The highperformance solar cell will be achieved by reducing the work function of transparent conductive oxides and increasing the carrier concentration in the TiCx layer. Finally, TiCx thin films substrate temperature and postannealing effect on the minority carrier lifetime of n-type monocrystalline silicon wafers with a-Si:H(i) and aSiOx:H(i) passivation layers were studied.

Substituting copper for silver in electrodes is a promising approach to cut down the production costs of silicon heterojunction (SHJ) solar cells. Nevertheless, the adhesion between electroplated copper electrodes and transparent conductive oxide layers, like indium tin oxide (ITO) layers, is crucial for the reliable and stable operation of these solar cells. In this research, magnetron sputtering is utilized to fabricate ITO layers for the SHJ solar cells with electroplated copper electrodes and how the sputtering parameters influenced the performance of the solar cells, particularly the adhesion at the Cu/ITO interface, is explored. The results demonstrate that ITO layers deposited with high sputtering power density and low oxygen flow rate show high crystallinity and low oxygen content, which can contribute to the enhanced adhesion to the electroplated copper electrodes. Conversely, ITO layers made with low sputtering power density or high oxygen flow rate contain more oxygen and have a decreased corrosion resistance, which detrimentally affect the adhesion at the Cu/ITO interface. These findings provide an applicable way to fabricate the efficient and stable SHJ solar cells with electroplated copper electrodes by optimizing the ITO deposition.

A low-high gradient doping bilayer stack of boron-doped hydrogenated nanocrystalline silicon (nc-Si:H(p)) was developed to modify the rear emitter for the silicon heterojunction (SHJ) solar cell on n-type crystalline silicon (c-Si(n)) substrate via depositing the first nc-Si:H(p) layer (p1) with low boron doping, followed by depositing the second nc-Si:H(p) layer (p2) with high boron doping. The p1 layer contributes to improve the short-circuit current density (JSC) of the solar cell due to its easily obtained high crystallinity (chi C). The p2 layer can effectively enhance the solar cell fill factor (FF) and open-circuit voltage (VOC) by improving its contact performance via the high doping, facilitated by the appropriate p1 layer. Based on adjusting the doping and the thickness combination of the p1 and p2 layers, combining with the interface modification on both sides of the p1/p2 stack, a 25.36 % efficient SHJ solar cell was successfully fabricated on the commercial large-area 166 mm x 166 mm (M6) c-Si substrate.

Nickel oxide (NiOx) hole transport layer deposited by magnetron sputtering shows high stability, low cost, high reproducibility, and scalability for perovskite and tandem solar cells. However, the performance of perovskite and tandem solar cells with sputtered NiOx is limited by the defective interface and suboptimal energy band alignment. This work focuses on reconstructing the sputtered NiOx surface with in situ biased plasma treatment (BPT). It is demonstrated that in situ BPT following sputtering induces both physical and chemical changes on the NiOx surface, enabling a smoother and denser surface with controllable Ni3+/Ni2+ ratios. The in situ BPT NiOx is proven to be effective in improving the conductivity of NiOx, suppressing the non-radiation recombination, fine-tuning the energy band alignment, and facilitating the crystallinity of the perovskite. As a result, the power conversion efficiency (PCE) of wide bandgap perovskite solar cells is improved to 21.8% by the implementation of BPT NiOx. Further integrating the BPT NiOx into monolithic perovskite/silicon tandem solar cells results in a high PCE of 32.1% (certified 31.7%) with excellent operational stability.

We introduce position-sensitive detectors (PSDs) based on femtosecond laser-structured sulfur-doped, nitrogen-doped, and S-N co-hyperdoped black silicon. In contrast to crystalline silicon, black silicon-based PSDs exhibit linear lateral photovoltage dependent on the light spot position. Thermal annealing at 873 K induces a tenfold enhancement in the position sensitivity of nitrogen-doped black silicon, reaching 129 mV/mm under white light irradiation. The device exhibits spectral response to 460-1150 nm wavelengths, achieving 99.7 mV/mm sensitivity with < 7% nonlinearity at 1000 nm under a low light power of 0.22 mW. These results demonstrate the potential of 873 K-annealed nitrogen-doped black silicon for self-powered, broadband PSDs with large sensitivity, high linearity, and ultra-low-light detection capability. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Ultraviolet (UV)‐induced degradation (UVID) poses a significant challenge for the prospective mass production of silicon heterojunction (SHJ) solar cells, known for their high efficiency. In this study, the magnified impact of UV radiation when employing a silicon carbide (SiC)‐based transparent passivating contact (TPC) on the front side of SHJ solar cells is reported. A reduction in open‐circuit voltage (VOC), short‐circuit current (JSC), and fill factor of 12%, 6%, and 11%, respectively, is observed after UV exposure. Conventional UVID mitigation measures, UV‐blocking encapsulation, are assessed through single‐cell TPC laminates, revealing an unavoidable tradeoff between current loss and UVID. Alternatively, the utilization of ultraviolet‐downshifting (UV‐DS) encapsulants is proposed to convert UV radiation into the visible light spectrum. An optical simulation method, conducted via OPAL2, is presented to evaluate UV‐DS encapsulants for diminishing UVID in SHJ solar cells with different front contacts. A simple methodology is proposed to mimic the optical property of UV‐DS encapsulants. In the simulation results, additional current gains of up to 0.33 mA cm−2 achievable with suitable UV‐DS encapsulants are highlighted. The factors related to the UV‐DS effects are evaluated and the optimization pathway for UV‐DS encapsulants is elucidated.

Self-assembled monolayers (SAMs) have emerged as highly promising hole transport layers for inverted perovskite solar cells, owing to their low parasitic absorption and effective charge extraction. However, their inherent strong hydrophobicity often inhibits the quality and uniformity of perovskite films and induces defects at the buried interface. In this study, a chlorine-substituted all-hydrophilic molecule is introduced to modify the buried interface. Such decoration transforms the hydrophobic SAM into a super-hydrophilic surface, significantly enhancing the quality and uniformity of perovskite films. This chlorine-substituted molecule exhibits a strong coordination with lead ions and effectively passivates defects at the buried interface of perovskite films. As a result, the single-junction wide-bandgap (1.67 eV) perovskite solar cell achieves a power conversion efficiency of 23.97%, the highest value achieved for MeO-2PACz-based devices. Furthermore, the perovskite-silicon tandem solar cell reaches an efficiency of 31.12%. Additionally, the applicability of chlorine-functionalized all-hydrophilic molecule at the buried interface modification is demonstrated to various SAMs (4PADCB, 2PACz and Me-4PACz) and narrower- or wider-bandgap (1.61, 1.68, and 1.72 eV) perovskite solar cells. This work presents a promising strategy to overcome the challenges associated with SAM-based perovskite solar cells, paving the way for further performance advancement.

NO2 gas sensing properties of the graphene oxide-decorated silicon (GO/Si) materials with abundantly exposed edge interfaces are studied. GO sheets are intermittently covered on the silicon surface treated with hydrophilic agents through a spin-coating process, enabling the formation of a sensing layer with optimized active surface area and diversified adsorption sites, which facilitate gas sensing. As the sensitive material in a conductometric gas sensor, far different from the respective planar Si and pristine GO, which exhibit poor repeatability and an undesirable n- to p-type response transition, the GO/Si brings about a qualitative change in sensing behavior, showing consistent p-type response to all tested concentrations and exhibiting good reproducibility. More interestingly, the coverage of GO can be simply adjusted by the hydrophilic treatment time. At an optimal hydrophilic treatment time similar to 1 second, the GO/Si sensor demonstrates an ultra-low theoretical detection limit of 188 ppt, along with high response, good selectivity, and long-term stability. The mechanisms behind the outstanding sensing performance are discussed, considering the exposed GO/Si edge interface and the synergistic effect of GO and Si.