新能源

The efficiency of perovskite solar cells has increased to a certified value of 27% over the past decade, benefiting from the superior properties of metal halide perovskite materials. However, their long-term operational stability is still far inferior to that of commercial crystalline silicon solar cells. A key source of this instability is field-driven ion migration in vertical architectures, along with the consequent degradation at the absorber-electrode interfaces. Compared with the widely investigated vertical structures, back-contacted (BC) perovskite solar cells-wherein both electrodes are positioned on the same side of the absorber-offer a unique route to suppress interfacial ion migration and thereby enhance long-term device stability. These advantages are especially pronounced when combined with single-crystal perovskites, which possess low charge trap densities, long carrier diffusion lengths, and high bulk ion migration barriers. Unfortunately, only a handful of research groups have participated in the development of single-crystal BC perovskite solar cells; thus, the advancement of this area lags far behind that of its vertical counterpart. Therefore, a review that discusses the recent developments and challenges of single-crystal BC perovskite solar cells is urgently required to provide guidelines for this emerging field. In this progress report, we first introduce the main growth methods of single-crystal wafers compatible with BC architectures, followed by an outline of the developmental history of BC perovskite solar cells. Finally, the core bottlenecks facing single-crystal BC devices and corresponding optimization strategies are discussed in detail.

Antimony sulfide (Sb2S3), an emerging photovoltaic material, is desirable for efficient, cost-effective solar cells, attributed to its capability to achieve highly crystallized Sb2S3 films by nonvacuum techniques, favoring the design of all-solution-processed photovoltaics. A high-performance Sb2S3 solar cell often constitutes hydrophobic hole-transporting layers, creating a surface energy mismatch with hydrophilic solution-processed, effective transparent conductors (TCs) like silver nanowires (AgNWs). Therefore, the realization of an efficient, all-solution-processed Sb2S3 solar cell remains challenging. Herein, a completely solution-processed Sb2S3 solar cell is achieved by designing an effective AgNW-based TC by intermixing an AgNW solution with 27 vol % poly(3-hexylthiophene) (P3HT). An interaction between isopropyl alcohol, a polar solvent in the AgNW solution, and P3HT results in the aggregation of the polymer, enhancing adhesion between the AgNWs and the glass/FTO/TiO2/Sb2S3/P3HT surface. This technique enables a reduction in the sheet resistance of AgNW-based TCs by 88%. The Sb2S3-based solar cells with modified AgNW-based TCs provide an efficiency of 2.1% and a consistent open-circuit value of 0.7 V for up-scaled devices. The adaptation of TCs allows the device to work in bifacial mode with a see-through feature, evidenced by an average visible light transmittance of 11.7%. The developed all-solution-processed Sb2S3-based semitransparent photovoltaics would be advantageous for photovoltaic-integrated product applications.

This study presents a comprehensive diagnostic analysis of two inverted metamorphic Al0.09Ga0.42InP/Al0.2GaAs/GaAs/In0.17GaAs/In0.46GaAs five-junction solar cells (IMM-5JSCs) with AM1.5G efficiencies of 35.5% and 33.4%, utilizing an integrating-sphere-based absolute electroluminescence (EL) measurement technique. A systematic theoretical framework is developed to extract the dark and illuminated current density-voltage (J-V) characteristics of individual subcells from absolute EL spectra, with full consideration of luminescence coupling (LC) effects. Through external radiative efficiency (ERE) analysis, we achieve a cross-institutional comparison of crystal quality with subcells of the NREL-reported IMM-6JSC and uncover the root causes of performance discrepancies between the devices. The AlGaInP and GaAs subcells in our IMM-5JSCs exhibit comparable or superior lattice quality, while the AlGaAs and In0.17GaAs in IMM-5JSCs show slightly inferior quality, and the In0.46GaAs subcell demonstrates the poorest material quality. The EL-derived subcell light J-V characteristics yield overall open-circuit voltage and short-circuit current density predictions that closely match experimental values, with deviations within 36 mV and 0.04 mA/cm2, respectively, but fill factor (FF) and conversion efficiency were overestimated by approximately 3% and 1%. Based on these diagnostic findings, we propose and compare targeted optimization strategies. This work provides a reliable, non-contact diagnostic tool for evaluating subcell performance in complex multijunction architectures, identifies optimization directions through comparative device analysis, and offers actionable guidance for advancing IMM-5JSC performance.

Although the optimized structures of the photoactive species have driven a rapid development in third-generation solar cells in the past decade, minimizing interfacial loss is another critical factor for achieving high-performance devices. Self-assembled monolayers (SAMs) have emerged as an effective approach to modulate the interface between materials to enhance device performance and stability, serving as alternatives to the conventional polymeric hole-transporting layers. In this Review, we first provide a systematic analysis on each structural component of SAMs, while elucidating the underlying mechanisms of their characteristic advantages. Furthermore, we investigate their applications in both perovskite solar cells and organic photovoltaics, emphasizing their role in highly efficient solar cells. Finally, we propose the future research direction of the field for large-scale manufacturing and commercialization. The structure-property relationships discussed in this Review will serve as a foundation for the optimized designs of SAMs, offering insights into achieving theoretical limits in next-generation devices.

The toxicity issues with lead-based perovskite solar cells sparked interest in lead-free alternatives, such as K3Ti2Cl9-x Br x (x = 0, 3, 6, and 9), which are environmentally friendly. The optical, structural, and electrical properties of K3Ti2Cl9-x Br x (x = 0, 3, 6, and 9) are investigated using density-functional theory in this study to assess their potential as absorber materials for solar cells. Phonon dispersion is used to determine the dynamical stability of these perovskites in addition to their formation energy, which further provides evidence regarding their stability. The TB-mBJ indicates its direct bandgap along the M-M direction and indirect bandgap at the M-K direction and lie within the ideal range for photoelectric conversion. The SCAPS-1D program is employed to identify the optimal solar cell designs that integrate various ETLs and HTLs. The structure with the highest power conversion efficiency out of the fifty four configurations examined is FTO/WS2/K3Ti2Cl9-x Br x (x = 0, 3, 6 and 9)/CuI, provides the highest performance with an efficiency of 19.11, 24.68, 25.25 and 29.00%, FF of 82.14, 81.53, 80.09 and 62.07%, V oc of 1.30, 1.29, 1.25 and 1.35 V and J sc of 17.84, 23.42, 25.88 and 27.00 mA cm-2 with the addition of recombination effect. Additionally, the effect of thickness, defect density, series and shunt resistance is also examined. Photocatalytic analysis shows that all of these compounds are capable of converting H2O to O2 and H2. In the same way that the compounds under study may reduce N2 to NH3, they can likewise reduce CO2 to CH4OH and CH4. In comparison to other materials, these compounds have an effective efficiency for reducing CO2 and N2 and their photocatalytic efficiency for water splitting is higher than the intended value for industrial applications. Future research should focus on developing lead-free, totally inorganic perovskite photovoltaics and photocatalysts with enhanced photovoltaic and photocatalytic performance. Such materials could have uses in photocatalysis, especially in visible light-driven processes like water splitting, CO2 reduction, and N2 fixation and are highly promising for use in photovoltaics and high-performance optoelectronics because they all have absorbers with strong visible-light absorption, a large PCE, and a high quantum efficiency.

All-perovskite tandem solar cells (APTSCs) have attracted considerable research interest in recent years due to their higher theoretical efficiencies and broader spectral coverage. Nonetheless, as the bottom narrow-bandgap cell in APTSCs, tin-lead (Sn-Pb) hybrid perovskite solar cells (PSCs) still face challenges of high defect density and poor crystallization morphology, which hinder the further improvement of device performance and long-term stability. This work proposes a Lewis hard-basicity amplification strategy that provides additional potential hard-acid binding sites and promotes coordination with Sn2+, thereby enabling defect passivation and regulating crystallization. Ultimately, we achieved a champion power conversion efficiency (PCE) of 23.71% for single-junction Sn-Pb PSCs. By integrating 1.77 eV wide-bandgap perovskites with Sn-Pb hybrid perovskites, we further fabricated APTSCs with a champion PCE of 29.44%. Both devices retain approximately 80% of their initial efficiency after 1080 h of continuous operation under one-sun illumination.

This study presents a comprehensive SCAPS-1D simulation of an ultra-thin CIGSe/CdS/i-ZnO/ITO solar cell with a 420 nm absorber layer, focusing on the influence of key physical parameters and back surface field engineering. The effects of acceptor doping density in CIGSe (N a = 1013 to 1018 cm-3), interface defect density (N i-t = 109 to 1018 cm-3), bulk defect density (N t = 1012 to 1020 cm-3), and electron affinity (χ = 4.35-4.65 eV) were systematically investigated. Increasing N a significantly enhanced device performance by strengthening the internal electric field and increasing the carrier concentration, thereby improving V oc, fill factor, and efficiency. In contrast, elevated interface and bulk defect densities led to severe recombination losses and significant degradation of all photovoltaic parameters. Optimal band alignment was obtained at χ ≈ 4.35 eV, corresponding to a slight negative conduction-band offset that facilitates carrier transport and suppresses recombination. Recombination analysis showed stable performance of the radiative recombination coefficient over the range 10-16 to 10-8 cm3 s-1, while Auger recombination became dominant at coefficients above 10-23 cm6 s-1. Among the investigated back surface field layers, Cu2O provided the best performance due to its wide band gap (2.2 eV) and strong back-surface electric field, yielding a maximum simulated efficiency of ∼40.3% with V oc = 0.817 V, J sc = 30.03 mA cm-2, and FF = 82.88%. Capacitance-voltage and Mott-Schottky analyses revealed that capacitance increases from 57.6 to 109.9 nF cm-2 with increasing N a, and the built-in potential ranges from 0.80 to 1.32 V, confirming enhanced junction properties. These results provide practical guidelines for optimizing ultra-thin CIGSe solar cells through defect control, band alignment tuning, and back surface field design.

Cu2ZnSn(S,Se)4 kesterite solar cells, while promising for sustainable photovoltaics, are constrained by undefined crystallization kinetics during selenization, which introduces bilayer crystallization with detrimental horizontal grain boundaries, voids, and secondary phases. This work traces this issue to early-stage Se-driven reaction at the back interface, which forms a low-melting-point Cu(S,Se) phase and triggers uncontrolled reverse crystallization. To address this, we propose a thermal-decoupled selenization strategy that creates a vertical Se concentration gradient in the initial stage. This approach decouples Se supply from the Cu(S,Se) formation temperature range, thereby suppressing bilayer crystallization. Consequently, it enables the growth of top-down columnar grains, which enhance carrier transport and suppress recombination, achieving a champion power conversion efficiency of 15.7% (certified 15.3%) in the resultant devices. This approach offers critical insights into crystallization kinetics and is also applicable to solution-processed Cu(In,Ga)Se2 solar cells, highlighting its great significance for diverse copper-based chalcogenides.

The unclear mechanisms and dominant types of defects causing degradation hinder the stability of perovskite solar cells, leading to increased operating costs and limiting their commercialization. In this study, we identify deep-level IFA and IPb defects as the primary cause of device degradation based on quantitative analysis of capacitance-frequency spectra combined with detailed balance theory, although the concentrations are lower than those of commonly believed shallow-level defects by three orders of magnitude. To mitigate these issues, we design a non-intercalary ligand coordination strategy through dual-end electropositive 3TU2+ ions, which effectively passivated the degradation-induced deep-level defects. This approach results in a significant improvement in quasi-Fermi level splitting alignment, reducing energy loss at the rear interface by an order of magnitude (from 1.46% to 0.62%). In addition to achieving a certified efficiency of 25.56%, our devices demonstrate an extrapolated T80 lifetime exceeding 10 years, as per the ISOS-LC-1 protocol. This improvement reduces the levelized cost of energy to 0.148$ kWh-1, on par with silicon photovoltaics, thus enhancing the commercial viability of perovskite solar cells.

Perovskite solar cells (PSCs) offer exceptional tunability of optoelectronic properties, enabling wide-band-gap absorbers that are highly attractive for semitransparent devices in building-integrated photovoltaics (BIPV). However, challenges associated with stability, scalability, and materials' cost continue to limit their practical deployment, highlighting the pivotal role of hole transport materials (HTMs) in achieving high efficiency and durable device operation. Herein, we report the rational design and synthesis of three novel small-molecule HTMs based on phenothiazine-triarylamine cores, prepared via concise synthetic routes with moderate-to-high yields. The electron-rich, nonplanar phenothiazine scaffold enables suppressed aggregation and favorable energy-level alignment, rendering these materials particularly suitable for wide-band-gap and semitransparent PSCs. When implemented in FAPbBr3-based semitransparent devices, two candidates (SM1 and SM2) achieve power conversion efficiencies comparable to those of the state-of-the-art poly(triarylamine) (PTAA) (PCE = 6.26% and 6.09% for SM1 and SM2, respectively, vs 6.39% for PTAA). Notably, their enhanced optical transparency leads to comparable light-utilization efficiency (LUE) (4.05 and 3.99 for SM1 and SM2, respectively, vs 4.07 for PTAA), with outstanding and superior bifaciality factors (84% and 82% for SM1 and SM2, respectively, vs 81% for PTAA), providing a distinct advantage beyond conventional opaque-PV efficiency metrics. These findings position phenothiazine-based HTMs as promising, cost-effective alternatives to PTAA for scalable semitransparent perovskite solar cells.

Perovskite solar cells (PSCs) have garnered significant attention due to their outstanding optoelectronic properties and ease of fabrication. However, their commercialization is hindered by high costs and stability issues associated with the Hole Transport Layer (HTL) and the high cost of back contacts. In this study, a novel, cost-effective, HTL-free PSC structure using a lead-free CsSnI3 absorber and WS2 electron transport layer (ETL) is designed and optimized using SCAPS-1D simulation. The device performance was enhanced by systematically optimizing key parameters, including layer thickness, doping concentration, defect density, and series/shunt resistance. The optimized cell, utilizing a Nickel (Ni) back contact, achieved a Power Conversion Efficiency (PCE) of 26.08%, with an open-circuit voltage (Voc) of 0.94 V, a short-circuit current (Jsc) of 34.84 mA/cm2 and a fill factor (FF) of 79.89%. This design offers a highly efficient, nontoxic, and economically viable alternative by replacing traditional, expensive HTL/metal contact combinations (>500 euros/g) with Ni, which costs only ∼2.23 euros/g.

The crystallization kinetics of all-inorganic perovskites critically influence the photovoltaic performance. Here, we introduce formamidinium acetate (FAAC) as a multifunctional additive to promote the conversion of DMAPbI3 and Cs4PbI6 intermediates into high-quality black-phase γ-CsPbI3 thin films. FAAC reduces the formation energy of the Cs4PbI6 intermediate, enabling its early formation during initial heating. Concurrently, FA+ cations rapidly intercalate into the DMAPbI3 lattice, forming a mixed (FA, DMA)Pb(I, AC)3 phase that facilitates complete cation exchange between DMA+ and Cs+ and accelerates DMAI removal. This synergistic effect effectively reduces residual DMA+ and structural defects. The optimized FAAC-based CsPbI3 perovskite solar cells (PSCs) achieve a power conversion efficiency (PCE) of 21.84%. Furthermore, the unencapsulated devices exhibit excellent operational stability, retaining 90% of their initial efficiency after 500 h under ambient conditions and 88.7% after 120 h of thermal aging at 85 °C.

We systematically investigate PM6:Y12 bulk-heterojunction solar cells with donor fractions ranging from 1% to 45%, linking morphology, charge transport, and recombination to device performance. Complementary structural and spectroscopic methods reveal that a percolating PM6 network forms even at below 5% donor content, with lamellar stacking and vertical composition gradients that do not hinder the charge extraction. The reduction of the effective active layer conductivity toward low donor fractions obeys a three-dimensional percolation model, indicating that charge transport is governed by network topology rather without a pronounced percolation threshold. A transition from nongeminate Langevin recombination to a dispersive Smoluchowski-type loss occurs below 5% donor fraction. The latter regime is also nongeminate, i.e., pertains to recombination of the total charge carrier density. Correspondingly, we observe that the Langevin reduction in the higher donor fractions - mostly dominated by redissociation of electron-hole pairs after encounter - changes toward low donor fractions: in these cases, the nongeminate loss rate exceeds the prediction of the Langevin model. This regime coincides with increasing transport resistance due to topology-limited hole conduction, leading to reduced fill factors despite a high retained charge-generation efficiency. Our results demonstrate that strong donor dilution preserves photogeneration if a continuous donor network is maintained, and unveil how topology-controlled transport and non-Langevin recombination jointly define the performance limits of donor-diluted organic solar blends.

Precise bandgap tuning is critical for maximizing the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Here, we refined the Shockley-Queisser model by incorporating sub-bandgap absorption and nonradiative losses, predicting an optimal optical bandgap (Eg) of ∼1.41 eV for Y-series acceptor-based OSCs, higher than the ideal SQ value of 1.34 eV. Guided by this loss-aware target, we designed and synthesized a new acceptor (YCF3-BO) with CF3-terminated core- and branched outer-side chains to achieve the target Eg in PM6:YCF3-BO devices. The resulting binary and ternary devices achieved PCEs of 19.8% and 20.2%, respectively. This performance arises from two synergistic effects: tuning Eg into the refined optimum window enhances photoluminescence quantum yield and suppresses nonradiative recombination, while branched side chains promote a 3D charge-transport network. Furthermore, PM6:YCF3-BO-based photocathodes operated efficiently in underwater solar hydrogen production. This study establishes a unified framework integrating loss-aware bandgap theory with acceptor design and solid-state packing control for advancing organic photovoltaics.

The excellent optoelectronic properties of transparent conducting oxides (TCOs) are critical for achieving highly efficient thin-film solar cells (TFSCs). In this regard, Mg- and group III-codoped ZnO-based compounds are highly promising TCO materials owing to their wide optical spectra, high transmittance, and electrical properties. However, detailed investigations of TFSC applications remain elusive. In this study, we systematically investigated the detailed relationship between various electrical properties (i.e., carrier concentrations and mobility conditions) and the device parameters for kesterite-based TFSCs. In particular, a quantitative analysis of scattering, detailed Eg-widening mechanisms in TCOs, and their effects on the quantitative deconvolution of series resistance and TFSC performance is discussed. As a result, the photocurrent densities and fill factors in TFSCs are strongly related to the electrical properties of the TCO, whereas the open-circuit voltages remain constant regardless of the TCO material. Among the investigated TCO materials, the Mg and Ga-codoped ZnO TCO layer exhibits favorable band alignment and high transmittance compared with the other layers, significantly enhancing charge transport and suppressing recombination at the interface in TFSC devices. These findings offer new insights into the fundamental impact of wide-optical-bandgap energy TCOs on charge transport, interfacial recombination properties, and overall device performance in inorganic-based TFSC devices.

Quantum dot solar cells (QDSCs) have emerged as promising next-generation photovoltaic technologies owing to their tunable bandgaps, strong light absorption, solution-processability and potential to surpass the Shockley-Queisser efficiency limit through multiple exciton generation (MEG). This review presents a comprehensive and critically structured overview of recent advances in QDSCs by integrating material development, device engineering, interface optimization, and stability enhancement strategies within a unified framework. Unlike previous reviews that primarily focus on individual material systems or device architectures, this work systematically correlates quantum dot absorber materials, electron and hole transport layers, electrode engineering, fabrication methodologies, and charge-transfer mechanisms with photovoltaic performance metrics. Emphasis is placed on the comparative analysis of PbS, CdSe, perovskite, graphene and environmentally benign quantum dots, highlighting their influence on efficiency, charge transport, stability, and scalability. In addition, recent developments in interface engineering, ligand exchange, surface passivation, core-shell structures, plasmonic enhancement, and hybrid architectures are critically discussed as key routes for suppressing recombination losses and improving long-term operational stability. Emerging trends including AI-assisted device optimization, tandem configurations, and environmentally sustainable QD materials are further evaluated to identify future commercialization pathways. Despite significant progress, challenges associated with toxicity, large-scale fabrication, and environmental stability continue to limit practical deployment. Overall, this review provides a comparative and future-oriented perspective that bridges materials science, device physics, and scalable engineering approaches, offering strategic insights for the development of efficient, stable, and commercially viable QDSCs for next-generation solar energy technologies.

In this paper, we design and analyze a new family of organic dyes for application in dye-sensitized solar cells (DSSCs). In particular, we performed a computational examination on novel engineered dyes incorporating triethylamine as the electron-donating group, a conjugated hexyloxy-substituted benzene-PQ bridge, and various electron-accepting units. The computational study was carried out using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Consequently, we investigate various key features, including frontier molecular orbitals (FMOs), global reactivity descriptors, density of states (DOS), molecular electrostatic potential (MЕP), charge transport and transfer proprieties, and optical and photovoltaic characteristics. Therefore, all developed dyes demonstrate high electron transport efficiency in comparison to hole transport, strong optical features, and good electron-donating and accepting capabilities. In order to assess interfacial charge transfer, dye adsorption on the (TiO2)8 cluster was also investigated. The results indicate efficient charge injection between the dye molecules and the TiO2 surface. In general, computational findings provide excellent proof to test experimentally these dyes because they are anticipated to greatly enhance DSSC performance.

Additive engineering has shown great potential in modulating crystallization kinetics and reducing defects in quasi-2D perovskite films. However, most studies have primarily focused on the types of functional groups, while the influence of their spatial configuration remains largely overlooked. Here, we systematically investigate the impact of functional group configuration on quasi-2D perovskite solar cells using an isomeric molecular pair, cytosine and iso-cytosine, as a model system. Despite sharing identical functional groups, their distinct spatial configurations lead to different charge distributions and interactions with the perovskite components. Consequently, cytosine exhibits stronger and more delocalized interactions that promote favorable nucleation and crystallization, yielding more ordered film structures, whereas iso-cytosine shows comparatively weaker and more localized interactions. As a result, cytosine-based devices achieve a champion power conversion efficiency of 22.4% and demonstrate excellent thermal stability, with over 80% of the initial performance retained after 3600 h of thermal aging at 60 °C.

Morphology is a critical determinant of the photovoltaic performance of organic solar cells (OSCs), as it governs charge generation, separation, and transport by regulating nanoscale phase separation and molecular packing within the active layer. Among the various strategies developed to control morphology, solid additives (SAs) have emerged as a particularly promising approach. Offering advantages such as low cost and ease of incorporation, SAs enable precise tuning of active layer morphology without the need for complex synthetic modification. By promotion of favorable nanoscale phase separation, SAs can facilitate the formation of well-organized domains that enhance charge transport pathways while reducing charge recombination losses. Recent advances have underscored the significant potential of SA engineering in advancing OSCs toward large-scale commercial deployment. This review provides a comprehensive summary of recent progress in SA development with a particular emphasis on their roles in regulating film formation dynamics and optimizing morphologies. Finally, we highlight the remaining challenges and propose future research directions to further exploit SA engineering in the realization of high-efficiency, stable organic photovoltaic devices.

Scalable manufacturing of high-efficiency perovskite solar cells (PSCs) requires blade coating not only of the perovskite layer, but also of other functional layers, including organoammonium halide surface passivation layers and self-assembled monolayers (SAMs), under ambient conditions. However, organoammonium iodides and SAMs are highly hygroscopic and prone to hydrolysis and desorption, respectively, and they are commonly processed from hygroscopic alcohol. As a result, despite its importance for scalable production, ambient blade coating of these moisture-sensitive interfacial layers has rarely been demonstrated. Here, we report a general low-hygroscopic solvent system for blade coating hygroscopic organoammonium halides and SAMs. We mix alcohol with low-polarity alkane, where the alcohol dissolves the functional materials and the alkane suppresses moisture uptake during the blade-coating process under ambient conditions. Comprehensive chemical and optoelectronic characterizations confirm that low-hygroscopic solvent system is a general approach to blade coat both passivation layers and SAMs under high humidity. The devices with air blade-coated SAMs, perovskite, and passivation layers achieve a certified efficiency of 26.1% with negligible decrease even fabricated at 80% relative humidity. This work solves one of the most challenging issues of scalable fabrication of perovskite photovoltaics in ambient air.