Gradient heating dissolution of active materials enhances the performance of organic solar cells

Effects of Ag + Ag-coated Cu metallization on the structure and performance of n-TOPCon solar cells

Understanding the microstructural evolution of perovskite films is crucial for optimizing the performance of perovskite solar cells (PSCs). In this study, we systematically investigated the impact of interface modification on perovskite crystallization using high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED). While maintaining identical perovskite deposition conditions, the planar structure PSC device exhibited disordered grain orientations and irregular lattice fringes, whereas the mesoscopic structure device demonstrated a well-ordered crystal lattice extending from the TiO2 interface to the perovskite surface. Dark field TEM (DF-TEM) further confirmed that this structural continuity persisted throughout the entire perovskite film in the mesoscopic structure, in contrast to the planar structure where coherent crystal domains were confined to isolated regions near the compact TiO2 interface. SAED analysis revealed that adjacent grains in the mesoscopic structure share a consistent crystal orientation, whereas the planar structure exhibited largely uncorrelated diffraction patterns between grains. These structural differences, undetectable by conventional XRD or surface SEM, directly correlate with the improved photovoltaic performance as high as 20.8% photoconversion efficiency in the conventional CH3NH3PbI3 device without additional doping or passivation treatment. These findings highlight the critical role of interface engineering in directing perovskite crystallization, providing insights into improving efficiency through microstructural control.

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.

Perovskite solar cells (PSCs) utilizing self-assembled monolayers (SAMs) as hole transport layers (HTLs) have been successful. However, the integrity of SAMs is frequently compromised by organic solvent-induced erosion during subsequent deposition of perovskite films. To overcome this critical stability issue without increasing fabrication complexity, we propose a novel strategy in which SAM molecules are directly doped into the perovskite precursor solution. The in situ doping approach effectively compensates for solvent erosion, thereby enhancing the SAM coverage, improving the perovskite crystallinity, and significantly reducing the trap density at the buried interface. Consequently, the optimized devices exhibit superior film quality and a more robust HTL/perovskite interface, yielding a power conversion efficiency (PCE) of 25.16% and enhanced thermal and light stability. This straightforward approach offers a promising pathway for the development of low-cost, high-performance photovoltaic technologies.

The morphological instability of the active layers remains a critical bottleneck limiting the photovoltaic performance and long-tern operational stability of organic solar cells (OSCs). In this work, the synergistic mechanism of the conjugated polymer PM6 and halogenated alkane additive 1,8-diiodooctane (DIO) was systematically investigated to understand the effect on the microstructure and photovoltaic performances of the D18:BTP-BO-4F-based OSCs active layer. The results demonstrate that the co-introduction of PM6 and DIO effectively refines the phase separation morphology, modulates donor-acceptor molecular aggregation, and promotes favorable nanoscale domain connectivity. This synergistic approach not only enhances the carrier transport and extraction but also significantly inhibits both monomolecular and bimolecular recombination losses. Consequently, the power conversion efficiency of the binary OSCs increases from 16.68% to 19.37%, accompanied by an open circuit voltage of 0.882V, a short-circuit current density of 28.45mA cm-2, and a fill factor of 77.14%. Furthermore, devices fabricated using this synergistic strategy retain over 90% of their initial efficiency after 60 d of storage under inert atmospheric conditions. These findings underscore the critical role of the conjugated polymer-additives synergy in directing active layer morphology regulation, thereby offering a robust and scalable strategy for concurrently improving the efficiency and stability of OSCs.

The severe nonradiative recombination losses in Cs2AgBiBr6 solar cells limit the enhancement of their open circuit voltage (VOC). Enhancing the built-in electric field (BEF) can help suppress the nonradiative recombination and effectively reduce the VOC and power conversion efficiency (PCE) losses. In this study, we introduced ferroelectrics diisopropylammonium hydrobromide (DIPAB) as an interfacial layer between the Cs2AgBi0.997Fe0.003Br6 film and the hole transport layer Spiro-OMeTAD in Cs2AgBi0.997Fe0.003Br6 solar cells. The ferroelectricity of DIPAB increases the BEF significantly. Additionally, the incorporation of DIPAB effectively passivates the defects and optimizes the energy-level alignment. Ultimately, DIPAB-modified Cs2AgBi0.997Fe0.003Br6 solar cells achieve a PCE enhancement from 2.81% to 3.43% and yield a VOC of up to 1.295 V, which is among the highest VOC documented for Cs2AgBiBr6 solar cells to date. Moreover, the unencapsulated DIPAB-modified Cs2AgBi0.997Fe0.003Br6 solar cells maintain 86% of its initial PCE after aging for 30 days at 25 ± 5 °C and 60 ± 5% relative humidity and 88% after aging for 300 h at 60 °C in a nitrogen glovebox. This study highlights the significance of ferroelectrics in enhancing the performance and stability of Cs2AgBiBr6 solar cells.

The design of interlayer materials featuring precisely matched electronic properties with the active layer materials and robust thickness tolerance is crucial for advancing organic solar cell (OSC) performance and commercialization. Zwitterionic polymers have been investigated extensively as interlayer materials in organic electronics. However, sulfobetaine (SB) has been the most widely adopted zwitterionic chains, while other cation-anion combinations remain largely unexplored, and the contribution of the anionic groups in zwitterions is still a mystery. Here, we explored a bioinspired zwitterionic interlayer material, engineered through the synergistic integration of fluorinated phosphatidylcholine-based polar side chains and an acceptor-acceptor (A1-A2) conjugated backbone. Such a synchronous side chain/backbone "surgery" simultaneously achieves deep frontier molecular orbital energy levels aligned with state-of-the-art electron acceptors, suppressed parasitic absorption, highly ordered molecular packing, and reduced hydrophilicity. The resulting interlayer material, PDITz-PC, demonstrates strong work function modification, superior electrical properties, and excellent interfacial contact. In OSCs, PDITz-PC enables impressive power conversion efficiencies (PCEs) for both small area (0.04 cm2) and large area (0.6 cm2) devices across various active layer systems, accompanied by significantly improved operational device stability, attributed to enhanced exciton dissociation, improved charge transport, and suppressed charge recombination. Notably, PDITz-PC exhibits good thickness tolerance, solar cells retaining 92% of the peak PCE even at an interlayer thickness of 115 nm. This work highlights the critical need to synchronize interlayer design with advancements in active-layer materials via the harmonized engineering of side chains and backbones, offering a strategic route to achieving high-performance, durable, and scalable organic photovoltaics.

Quantum and classical machine learning for perovskite bandgap learning and solar cell performance analysis

The degradation of metal halide perovskite surfaces induced by H2O and O2 molecules severely limits the performance and practical application of perovskite solar cells. In this work, density functional theory (DFT) calculations are performed to systematically investigate the degradation mechanisms occurring on the FAPbI3 (001) surface upon exposure to H2O and O2, and the resulting changes in electronic and optical properties. We find that the outermost Pb-terminated surface is particularly susceptible to degradation by H2O and O2, mainly due to the disruption of Pb-I bonds by these small molecules, which induces severe lattice distortion and further promotes molecular adsorption. H2O and O2 together adsorb more readily to the surface of the perovskite than when the two are present alone. Furthermore, a capping graphene layer can effectively prevent the permeation of H2O and O2 molecules, significantly improving the environmental stability of the perovskite. Graphene coating enhances both infrared and visible-light absorption, achieving a 16% increase in the visible range compared to the pristine surface. Graphene oxide provides superior blocking capability while further enhancing infrared absorption.

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.

The laggard advancement in electron transport layer materials is one of the bottleneck problems, impeding the further improvement of photovoltaic performance of perovskite solar cells (PSCs). Fullerene derivatives are widely used as electron transport layer materials for PSCs, but significant imperfections remain unresolved. Herein, an efficient and facile method was developed to prepare isomer-free multi-adduct fullerene derivatives, C60(NHR)4O, with high yield and meet the multifunctional requirements of electron transport layer materials of PSCs. Among the multi-adduct fullerene derivatives, tetra[methyl 2-amino-3-(thiophen-2-yl)propanoate]C60 epoxide (TATPC) was selected to incorporate into PCBM as an electron transport material for PSCs. Benefiting from multi-adduct groups, TATPC presents a higher LUMO energy level, superior passivation capability, and stronger interaction with perovskite than the classical PCBM. It enables PCBM:TATPC to afford improved coverage and a smoother surface, increased contact potential difference, reduced trap density, higher electron mobility, and inhibited self-aggregation, thus facilitating electron extraction, suppressing charge carrier recombination, and enhancing durability for PSCs. Therefore, PCBM:TATPC-based PSCs achieve an impressive efficiency of 26.66% (25.81% for devices with an area of 1.04 cm2) with enhanced operational stability. This work highlights an efficient molecular design strategy to develop isomer-free multi-adduct fullerenes and thus regulate the electron transport layer for high-efficiency and stable PSCs.

ABSTRACT The laggard advancement in electron transport layer materials is one of the bottleneck problems, impeding the further improvement of photovoltaic performance of perovskite solar cells (PSCs). Fullerene derivatives are widely used as electron transport layer materials for PSCs, but significant imperfections remain unresolved. Herein, an efficient and facile method was developed to prepare isomer‐free multi‐adduct fullerene derivatives, C 60 (NHR) 4 O, with high yield and meet the multifunctional requirements of electron transport layer materials of PSCs. Among the multi‐adduct fullerene derivatives, tetra[methyl 2‐amino‐3‐(thiophen‐2‐yl)propanoate]C 60 epoxide (TATPC) was selected to incorporate into PCBM as an electron transport material for PSCs. Benefiting from multi‐adduct groups, TATPC presents a higher LUMO energy level, superior passivation capability, and stronger interaction with perovskite than the classical PCBM. It enables PCBM:TATPC to afford improved coverage and a smoother surface, increased contact potential difference, reduced trap density, higher electron mobility, and inhibited self‐aggregation, thus facilitating electron extraction, suppressing charge carrier recombination, and enhancing durability for PSCs. Therefore, PCBM:TATPC‐based PSCs achieve an impressive efficiency of 26.66% (25.81% for devices with an area of 1.04 cm 2 ) with enhanced operational stability. This work highlights an efficient molecular design strategy to develop isomer‐free multi‐adduct fullerenes and thus regulate the electron transport layer for high‐efficiency and stable PSCs.

ABSTRACT The electron transport layer (ETL) is essential for the performance and stability of perovskite solar cells (PSCs). SnO 2 nanoparticles, widely employed as the ETL in n‐i‐p PSCs, often exhibit performance limitations arising from uncontrollable agglomeration and compromised interfacial quality, which in turn accelerates perovskite degradation. In this study, we propose a phosphate‐buffered synthesis strategy for SnO 2 nanoparticles, which enables effective proton buffering both during the synthesis process and at the perovskite/SnO 2 interface. Through regulating proton accumulation during SnO 2 nanoparticle formation, the phosphate buffer simultaneously enhances the colloidal dispersion stability of SnO 2 and introduces coordinated phosphate species at the SnO 2 /perovskite interface in PSCs. This phosphate interface effectively stabilizes FA + cations and suppresses deprotonation‐induced interfacial degradation. Devices incorporating phosphate‐buffer‐synthesized SnO 2 deliver a peak power conversion efficiency (PCE) of 26.1% and exhibit remarkable operational stability, retaining over 85% of their initial efficiency after 1000 h of continuous light exposure. Meanwhile, large‐scale PSC modules (65cm 2 ) achieve a PCE of 21.74%. This synergistic strategy provides a scalable and efficient solution for enhancing both the performance and stability of PSCs.

Two-dimensional transition-metal dichalcogenides (TMDs) (2D TMDs) have emerged as promising interlayer materials between SnO2 electron transport layer (ETL) and perovskite absorbers as they can effectively modulate the energy levels of SnO2 and facilitate the growth of perovskite crystals. However, the limited affinity of 2D TMDs for the SnO2 surface can result in inadequate coverage, which can adversely affect the performance of perovskite solar cells (PSCs). This study addresses this issue by incorporating polyacrylonitrile (PAN) to enhance the surface affinity of 2D tungsten selenide (WSe2). By utilizing the excellent dispersibility of the polymer, the PAN-WSe2 composite film achieves uniform dispersion and high surface coverage on the SnO2 layer. WSe2 features surface free of dangling bonds, a tunable electronic band structure, adjustable functional groups, and intrinsic compactness. These characteristics enable WSe2 to regulate SnO2's energy levels, passivate defects in the SnO2 ETL and functional layer, and alleviate interfacial stress due to its lattice matching with perovskite. This synergy results in perovskite films exhibiting higher crystallinity and lower defect density. Compared to SnO2-based PSCs, PAN-WSe2-modified PSCs demonstrate a significant enhancement in the power conversion efficiency, achieving an open-circuit voltage (VOC) of 1.18 V. Furthermore, after storage in nitrogen for 3800 h, PAN-WSe2-based PSCs retain 95% of their initial efficiency, highlighting their stability and potential for long-term applications.

Perovskite quantum dot (PQD) solar cells based on CsPbI3 have attracted considerable attention owing to their excellent optoelectronic properties. Continuous progress in ligand engineering has significantly improved their power conversion efficiency. However, limited attention has been paid to the hindered charge transport between the electron transport layer and the PQD layer caused by vacancy defects at the interface. Here, 6-aminonicotinic acid (AMC) molecules are introduced as a multifunctional interfacial modifier between the TiO2 ETL and the PQD layer to simultaneously passivate oxygen-vacancy defects and induce dipole-field-assisted interlayer charge transport. Experimental characterization and density functional theory calculations demonstrate that AMC molecules not only effectively passivate oxygen vacancies on the TiO2 surface but also accelerate electron extraction by regulating the interfacial energy-level alignment through dipole-field effects. Furthermore, interfacial modulation by AMC improves the crystallographic orientation and film uniformity of the PQD layer. As a result, the device efficiency is enhanced from 13.1 to 15%. This work provides an effective interfacial engineering strategy for improving charge transport and device performance in PQD solar cells.

Investigation of digital metasurface geometries for enhancing the performance of ultrathin silicon solar cells

Tin oxide (SnO2) has been widely used as an electron transport layer (ETL) in perovskite solar cells (PSCs) due to the excellent charge transport properties. In this work, we present a comprehensive computational and experimental investigation of a low-temperature strategy for developing Mg-doped SnO2 (Mg-SnO2) as an ETL to enhance the performance of indoor perovskite solar cells (i-PSCs). Experimental results demonstrate that Mg incorporation enhances optical transparency, increases the bandgap, and improves charge transport by reducing charge recombination at the ETL/perovskite interface. These enhancements lead to superior PCEs, achieving 35.54% under indoor LED illumination and 20.28% under standard one sun conditions, significantly outperforming undoped SnO2-based devices. Complementary density functional theory (DFT) simulations support the experimental findings, revealing that Mg doping decreases deep trap states, and contribute to improved ETL conductivity. The strong correlation between theoretical predictions and experimental outcomes underscores the effectiveness of Mg-SnO2 as a high-performance and stable ETL for indoor photovoltaic applications. This study establishes a practicalpathway for developing optimized Mg-doped electron transport layer for efficient indoor light harvesting.

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Characterization of cadmium-doped nZVI residuals: Structure, morphology, and photoelectrochemical properties