Aluminum-doped zinc oxide (AZO) film is a promising alternative to indium tin oxide (ITO), typical transparent conductive oxide (TCO) used in silicon heterojunction (SHJ) solar cells. However, the long-term damp heat (DH) stability of AZO-based SHJ devices remains a critical concern due to the moisture sensitivity of AZO. In this work, the mechanism of damp-heat-induced degradation (DHID) of AZO-incorporated SHJ solar cells and modules was systematically investigated and compared with ITO references. After 1000 h of DH exposure at 85 °C and 85% relative humidity, AZO-incorporated SHJ solar cells exhibited a larger efficiency loss than the ITO reference, mainly associated with a significant reduction in fill factor (FF). The FF degradation was strongly correlated with an increase in series resistance (Rs), and the increase in AZO film resistivity was identified as an important contributor to the Rs increase observed during DH exposure. X-ray photoelectron spectroscopy (XPS) revealed a pronounced increase in the OH− intensity after DH testing, suggesting moisture-induced chemical modification of the AZO surface or near-surface region. Moreover, the observed open-circuit voltage (Voc) degradation after DH exposure implies that moisture-related degradation may extend beyond the AZO surface and affect underlying passivation layers. In addition, scanning electron microscopy (SEM) revealed the formation of surface grooves on the AZO film after DH exposure. These observations, together with the electrical degradation of the AZO films and devices, are consistent with moisture-induced degradation of AZO. Furthermore, a MgF2 capping layer improved the DH stability of AZO-incorporated SHJ solar cells by mitigating moisture-induced degradation.

Self-assembled monolayer (SAM) hole transport layers are commonly used in state-of-the-art perovskite single-and multi-junction solar cells. Their precursor molecules are prone to aggregation. We report SAM-solution-pH-modulation that effectively suppresses aggregation, improving deposited film quality. We designed and synthesized a novel material, 6-aminohexylphosphonic acid hydrochloride (6AHPACl), to be added to the (4-(3,6-dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz) solution as part of a co-SAM strategy. Apart from the advantage of pH modulation, the inclusion of 6AHPACl improved SAM anchoring, SAM/perovskite interface energetics, and wettability of the overlaying perovskite layer and therefore its quality. This co-SAM strategy enabled demonstrations of a wide-band gap (1.67 eV) perovskite cell producing a champion efficiency of 22.8% and a 1 cm2 monolithic perovskite-silicon double junction cell producing a certified efficiency of 29.1%. An encapsulated device retained 95% of its efficiency after 1,010 thermal cycles (-40 degrees C to 85 degrees C). Another encapsulated double junction device surpassed the International Electrotechnical Commission (IEC) 61215 humidity freeze test.

During the development of perovskite-silicon tandem solar cells, the impact of transport layers of perovskite top cells on the short-circuit current density (J SC) has rarely been considered. Here, we report ultrathin electron-selective contacts as new architectures of electron transport layers (ETLs) by decreasing the C60 thickness to 1 nm, where the carrier collection efficiency is proven to be independent of C60 thickness with tin oxide as a buffer layer. Benefiting from the lowest C60 parasitic absorption, the J SC in the tandem device with ultrathin C60 is enhanced by 0.24 mA/cm2. Moreover, to recover the damage from atomic layer deposition on uncovered perovskite surface, we use poly(methyl methacrylate) (PMMA) as a protective layer. Combining ultrathin C60 and PMMA protective layer, an efficiency of 31.70% is finally achieved in tandem solar cells. These findings demonstrate the feasibility of ultrathin ETLs or ETL-free designs for perovskite-silicon tandem solar cells.

Zinc oxide thin films are successfully deposited using plasma‐enhanced chemical vapor deposition (PECVD), representing a novel approach for fabricating transparent conductive oxide (TCO) layers. The initial undoped ZnO film exhibits a polycrystalline structure with a pronounced (002) orientation and low optical absorptance. However, the electrical properties of the film are characterized by high resistivity and instability, primarily attributed to its porous morphology. These limitations can be addressed by incorporating aluminum‐doped zinc oxide or indium tin oxide seed layers, resulting in enhanced and more stable electrical performance. To demonstrate its applicability, this study reports the first successful integration of PECVD‐grown ZnO film as a front‐contact layer in silicon heterojunction solar cells. The addition of seed layers boosts the solar cell efficiency by increasing the fill factor through reduced series resistance. Despite the challenges with the initial film quality and the need to further refine the PECVD conditions to optimize the device performance, this study offers valuable insights into the current limitations and future potential of PECVD for TCO development. This lays the foundation for improving the PECVD process to produce high‐quality TCO, potentially establishing it as an alternative deposition method for next‐generation photovoltaic technology.

Hydrogen (H) is essential for the high performance of advanced crystalline silicon (c-Si) solar cells. Recently, H-related ultraviolet-induced degradation (UVID), which can compromise module stability, has attracted increasing attention from the photovoltaic (PV) industry, yet its underlying mechanisms remain incompletely understood. Here, the severity of UVID in silicon heterojunction (SHJ) solar cells is shown to depend strongly on the illuminated-side passivating-contact design, with transparent passivating contacts (TPCs) exhibiting markedly larger losses in open-circuit voltage (V OC), short-circuit current (J SC), and fill factor (FF) than conventional hydrogenated amorphous silicon (a-Si:H)-based SHJ contacts. Combined material characterizations and device analysis support a picture in which the high transparency of TPC shifts UV energy deposition toward the c-Si near-interface region, where UV-driven Si & horbar;H bond dissociation increases interfacial recombination and degrades chemical passivation. In parallel, UV exposure induces a pronounced resistivity increase in the hydrogenated nanocrystalline silicon carbide (nc-SiC:H) contact stack, consistent with local microstructural/electronic disorder and the possible involvement of enhanced sub-bandgap absorption, thereby raising series resistance (R s) and limiting carrier collection. Collectively, these findings link contact optical transparency, H-related bond dynamics, and nc-SiC:H transport degradation to the distinct UVID signatures of SHJ architectures.

In situ interface passivation serves as a crucial strategy for improving both the efficiency and stability of wide-band gap (WBG) perovskite solar cells and their associated tandem architectures. Here, we present a one-step in situ buried-interface passivation approach designed to reduce interface defects in three-dimensional (3D) WBG perovskite films. This is achieved by constructing self-assembly of a gradient Ruddlesden-Popper (RP) two-dimensional (2D) perovskite layer at the buried interface of the 3D WBG perovskite, leading to the formation of a gradient RP-2D/3D perovskite heterostructure. Such heterostructures facilitate the oriented growth of 3D perovskite crystals along the (100) plane, enhance charge carrier extraction, and effectively passivate trap states within the WBG perovskites. The in situ formation of RP-2D/3D perovskite heterostructures significantly enhances the light, thermal, and moisture stabilities of the WBG 3D perovskites. The resulting perovskite/silicon tandem solar cells exhibit improved current matching (mismatch 0.1% vs 5.5% for 3D), deliver improved efficiency of 32.73% (certified 32.46%), and demonstrate an operational lifetime T 90 exceeding 1508 h.

Lightweight photovoltaic (PV) applications are pivotal for expanding the adoption of solar energy, enabling new installation scenarios and contributing significantly to the renewable energy capacity. However, degradation due to ultraviolet (UV) radiation is a critical concern for silicon heterojunction (SHJ) solar modules, particularly lightweight solar module configurations, where flexible polymer-based front sheets may provide reduced shielding against UV radiation. In this study, we present a comprehensive investigation of the UV-induced degradation (UVID) behavior of lightweight SHJ solar modules utilizing encapsulants with different UV-transmission: UV-blocking, UV-transmitting, and UV-downshifting. After indoor UV exposure of 120 kWh/m2, equivalent to 30 months of outdoor exposure in J & uuml;lich, Germany, solar modules incorporating these encapsulants exhibited relative efficiency losses of 2.17%, 9.25%, and 6.15%, respectively. The decrease in efficiency was mainly attributed to a reduction in the fill factor (FF) of the solar modules, accompanied by a diminished pseudo fill factor (pFF). Based on detailed FF and pFF loss analyses, we found that pFF loss was the major cause of FF loss, which is attributed to the deterioration of the passivation properties due to UV radiation. Additionally, the influence of series resistance (R s)-related FF losses increased, which is attributed to the deterioration of the interconnection foil rather than the UV radiation itself. Additionally, while downshifting (DS) encapsulants helped mitigate UV damage, we observed a diminished DS effect in lightweight configurations, potentially due to photooxidation. Utilization efficiency of DS decreases from around 34% to 21% after 120 kWh/m2 of UV exposure. Therefore, a novel encapsulation architecture combining UV-downshifting and UV-blocking encapsulants was proposed to ensure the UV utilization and stability of lightweight SHJ solar modules. Solar modules featuring this innovative dual-layer structure preserved over 98% of their initial performance after UV exposure, demonstrating a promising new approach for enhancing UV stability. The comprehensive investigation provides substantial insights into the degradation mechanism of lightweight SHJ solar modules under UV exposure and offers practical strategies in the progress of improving their durability and performance.

This work investigates the influence of the metallization of low-temperature Cu paste and AgCu paste on the performance of SHJ solar cells through a comprehensive study of two techniques-screen printing (SP) and dispensing. The research successfully applied Cu and AgCu pastes as metal contacts on SHJ solar cells, yielding promising results. Notably, cells with AgCu paste SP on the front side and Ag paste SP on the rear side achieved a 0.13% efficiency gain over reference Ag SP bifacial cells. Moreover, cells with AgCu paste SP on the front side and Cu paste SP on the rear side reached an efficiency of 23.6%, just 0.35% lower than the reference cells, while saving approximately 70% of Ag paste. Cells with Cu paste SP on both sides recorded an average efficiency of 22.4% and a maximum of 23.08%, the highest efficiency reported for cells using Cu SP on both sides (zero Ag). Cells with Cu dispensing on the rear side also demonstrated superior performance compared to cells with Cu SP on the rear side. Along, we assessed the finger-printed characteristics of the three pastes and the performance of SHJ solar cells under various annealing conditions including the Cu annealing conditions (300 degrees C for 5 s). The solar cells maintained stable performance up to 280 degrees C for 5 s, with degradation observed above this temperature, and light soaking partially recovered some of the efficiency loss. A 0.2% drop persisted under Cu annealing conditions, but light soaking reversed this effect back to the original efficiency. This work advances SHJ solar cell technology by highlighting the potential of AgCu and Cu pastes to efficiently replace or reduce Ag paste consumption in SHJ solar cell metallization.

Advanced microscopy techniques have been employed to resolve the microstructure of transparent conductive oxide (TCO) contacts in silicon heterojunction solar cells. Aluminum-doped zinc oxide (AZO) stands out as a TCO material because of its low cost, abundance, and good optoelectrical properties. The polycrystalline AZO thin films have yielded promising results in solar cell design. However, understanding the nanostructure of AZO thinfilm materials is vital for enhancing the cell performance by focusing on the formation of large grains and their influence on the charge-carrier mobility of the film. Therefore, we employed high-resolution transmission electron microscopy (HRTEM) and precession-assisted four-dimensional scanning transmission electron microscopy (4D-STEM) with an automated crystal orientation analysis. These techniques can be used to determine the grain sizes of AZO films sputtered on hydrogenated amorphous silicon (a-Si:H) and hydrogenated nanocrystalline silicon (nc-Si:H) layers. Columnar grains in the AZO/a-Si:H film are evident in the grain mapping with diameters greater than 10 nm, whereas in the AZO/nc-Si:H film, the grains begin at diameters less than 10 nm, showing smaller grains near the substrate than at the top of the film. Additionally, the double-layer with indium-thin doped oxide (ITO)/AZO stack started with grain diameters varying from 5 to 90 nm. They exhibit significantly larger and irregular boundaries. Therefore, microstructural characterization showed that larger columnar grains might lead to higher mobility in the AZO layer. This finding indicates that the impact of the ITO seed layer on AZO significantly enhances grain size, improves charge carrier mobility, and overall improves the power conversion efficiency (eta) to be 23.6% comparable to those of AZO on a-Si:H and nc-Si:H.

Intensive light soaking (LS) is an effective post-treatment to boost the efficiency of hydrogenated amorphous Si (a-Si:H)/crystalline Si (c-Si) heterojunction solar cells. To date, devices have been annealed and illuminated with an intensity of up to 100 suns. Here, the potential of using an ultra-high-density light source equivalent to >10,000 suns is investigated by a scanning continuous-line-shaped infrared laser. It is clarified that the LS effect involves a reordering of H in the a-Si:H layers, which serves as the critical time-limiting process, triggered by carrier injection in c-Si and the associated induced heating. As a result, the local LS treatment increases carrier lifetime and efficiency by up to 400% and 1.3 %abs, respectively. While a laboratory-scale laser was used here, LS treatment via laser (scanning) offers substantial potential for scalability by employing an industrial laser with a larger irradiation area and higher power.

ABSTRACTLightweight photovoltaic applications are essential for diversifying the solar energy supply. This opens up vast new scenarios for solar modules and significantly boosts the capacity of renewable energy. To ensure high efficiency and stability of the solar modules, several challenges need to be overcome. Degradation due to elevated temperature and/or humidity is a critical concern for silicon heterojunction (SHJ) solar modules. Here, we investigated the stability and degradation mechanism of encapsulated cells with lightweight configurations where the cells are based on three different types of transparent‐conductive oxide (TCO): indium tin oxide (ITO), aluminum‐doped zinc oxide (AZO), and a combination of ITO/AZO/ITO under humid and thermal environmental conditions. A damp heat (DH) test at a temperature of 85°C and relative humidity (RH) of 85% was performed on lightweight modules for 1000 h. Our results show that AZO is the most susceptible to DH degradation. The AZO film was damaged by the combined effects of moisture ingress and delamination of the interconnection foil, resulting in a decrease in the conductivity of the AZO film, leading to a dramatic increase in Rs and a decrease in FF of the modules. Consequently, moisture has a greater chance of percolating through the damaged AZO layer into the a‐Si:H passivation layer, causing passivation degradation, which leads to an increase in recombination, resulting in a decrease in Voc of the modules. In particular, after capping the AZO film with an ITO film, the efficiency loss of the ITO/AZO/ITO module was significantly reduced. This suggests that the ITO film could be a promising protective capping layer for the AZO‐based solar cells.

A multiscale electro-optical device model is employed to investigate free energy and other losses in a silicon heterojunction (SHJ) solar cell. A finite element method-based device model is coupled with free energy loss analysis (FELA) to calculate detailed bias voltage-dependent losses in terms of mAcm(-2) and mWcm(-2). Such an approach provides insight into identifying possible pathways for synergetic optimization and redesigning a solar cell device in both laboratory and mass production settings. The SHJ solar cell investigated in this work demonstrates that the hole-selective contact (HSC) is responsible for a significant portion of the free energy loss. At maximum power point, a power density of similar to 1.6 mWcm(-2) at 1 sun is lost associated with carrier transport in HSC and recombination at both selective contacts. This results in a 1.6% absolute loss in power conversion efficiency (PCE). Auger recombination in the wafer limits the open-circuit voltage. The FELA suggests a pathway for synergistic optimization of the device to regain a significant portion of the similar to 2.6% absolute loss in PCE. Simultaneously adjusting the conductivity of a-Si layers in HSC and the concentration of free majority carriers in the wafer can improve the fill factor (FF) to similar to 87% and PCE close to 26%.

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.

Triple-junction solar cells theoretically outperform their double-junction and single-junction counterparts in power conversion efficiency, yet practical perovskite-perovskite-silicon devices have fallen short of both theoretical limits and commercial targets. To address surface defects in the top perovskite junction, we introduce a piperazine-1,4-diium chloride treatment, which replaces less stable lithium fluoride. For interfacing the top and middle perovskite junctions, we optimize the size of gold nanoparticles deposited on atomic layer-deposited tin oxide for best ohmic contacting with minimal optical losses. Applying these strategies, our champion 1-cm2 triple-junction cell achieved a third party-verified reverse-scan power conversion efficiency of 27.06% with an open circuit voltage of 3.16 V. Scaling up to 16 cm2, the device produced a certified steady-state power conversion efficiency of 23.3%. Device longevity also improved by eliminating methylammonium and incorporating rubidium into the perovskite bulk alongside the piperazine-1,4-diium chloride surface layer. An encapsulated 1-cm2 cell retained 95% of its initial efficiency after 407 h at maximum power point and passed the IEC 61215 thermal cycling test. These results represent advancements towards efficient and stable perovskite-perovskite-silicon triple-junction solar cells.

Lightweight photovoltaic (PV) modules are able to open up vast new scenarios for PV applications, like building-integrated PV (BIPV) and vehicle-integrated PV (VIPV). Silicon heterojunction (SHJ) solar cells have been recognized as one of the most advanced technologies for improving solar power generation. However, SHJ solar cells are inherently susceptible to damp heat-induced degradation (DHID), which is a critical concern for their application. In this study, lightweight SHJ mini-modules with a low area density (similar to 2 kg/m(2)) while preserving high power density (similar to 70 W/kg) were fabricated using SHJ solar cells with different encapsulation materials and architectures. A comprehensive analysis of the module degradation was carried out, focusing on the optical and electrical properties of the modules and the chemical properties of the encapsulants after 1000 h of accelerated damp heat (DH) aging test. The efficiency loss in lightweight SHJ solar modules after DH test varied significantly, ranging from 3.22 %(rel) to 54.06 %(rel), depending strongly on the encapsulation materials. The increase in series resistance (R-s) was generally the dominant cause of module efficiency degradation. An optimized damp heat-stable lightweight SHJ module was successfully fabricated, with only 0.47 %(rel) efficiency degradation after 1000 h of the DH test. Its stability is almost the same as that of the glass/back sheet module. The comparative study and comprehensive investigation provide insights into the DHID behavior of lightweight SHJ solar modules with different encapsulation materials, contributing to the development of lightweight SHJ solar modules with high DH stability for industrialized mass production.

This study introduces Direct Wire Bonding (DWB) as a low-temperature method for interconnecting finger-free Silicon Heterojunction (SHJ) solar cells using low-cost, highly conductive copper wires. The wires are attached to the SHJ cells via discrete pads of conductive paste, enabling direct current extraction from the indium tin oxide (ITO) layer and facilitating transport to sequentially connected cells. We describe the DWB fabrication process and demonstrate its potential by comparing its performance to that of traditional SHJ modules. Our test devices show that DWB modules achieve competitive efficiencies, 0.03 % abs. higher in experiments than the 0BB and multi-wire solutions-while significantly reducing material consumption. In the study we give an outlook on the possible improvement in efficiency. The economic analysis further demonstrates that DWB can reduce production costs to as low as 18 % of the cost of other SHJ metallization and interconnection techniques. These initial results suggest that DWB is a cost-effective solution that addresses both economic and material scarcity challenges in the photovoltaic industry.

Transparent passivating contact solar cells using hydrogenated n-type nanocrystalline silicon carbide (nc-SiC:H(n)) utilize a double-layer stack consisting of one passivation-optimized and one conduction-optimized nc-SiC:H(n) layer. This double-layer configuration limits the fill factor (FF) due to the passivating layer's low electrical conductivity. This study enhances this structure by introducing a gradient layer that transitions from passivating-like to conducting-like properties. While replacing the passivating layer alone does not improve performance, when combining it with an ultrathin passivating seed layer, the gradient layer effectively balances voltage and FF trade-offs. This results in higher device voltage and FF. Microstructural analysis shows hydrogen content near the crystalline Si interface similar to the double-layer approach but with increased electrical conductivity earlier in the layer stack. These improvements boost both FF and open-circuit voltage by 0.6% absolute and over 4 mV, respectively.

Crystalline silicon (c-Si) solar cells with hydrogenated nanocrystalline silicon carbide (nc-SiC:H)-based transparent passivating contact (TPC) achieve enhanced short-circuit current density (J(SC)) compared to conventional silicon heterojunction (SHJ) solar cells but suffer from lower open-circuit voltage (V-OC). The V-OC loss is largely due to sputter damage during Sn-doped indium tin oxide window layer deposition. We evaluate thermal annealing for damage mitigation but find limited restoration due to differing thermal tolerances of TPC and SHJ contacts. Instead, a direct heat-assisted intensive light-soaking (LiSo) treatment effectively heals the sputter damage, improving V-OC above 735 mV and achieving a certified efficiency of 24.17% +/- 0.29%. Detailed investigation highlights the synergistic effects of light and heat in the LiSo process. Additionally, a damage-restoration mechanism related to hydrogen motion is discussed.

Here, we report gas-quenched quasi-2D (GA)(MA)(5)Pb5I16 perovskites for single junction solar cells and monolithic-silicon tandem solar cells. This is the first time quasi-2D (GA)(MA)(5)Pb5I16 perovskite cells have been tested with proton beams, showing excellent tolerance. A representative tandem cell also passed the IEC 61215 Thermal Cycling Test (-40 degrees C <-> 85 degrees C) twice, retaining 95.0% of its initial PCE after 400 cycles.