Chen Weijie

This work reports hybrid self-assembled molecules (SAMs) formed by co-depositing [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) and thiol molecules on NiO _x , achieving an optimal efficiency of 25.40%. The island-like structure of the hybrid SAMs serves as atemplate for the formation of the perovskite bulk heterojunction composed of the interpenetrating networks of the MA-/FA-rich domains, enabling efficient charge generation and suppressed bimolecular recombination.

Abstract

Self-assembled molecules (SAMs) have been widely employed as hole transport layers (HTLs) in inverted perovskite solar cells (PSCs). However, the carbazole core of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) is insufficiently effective for passivating defects at the “bottom” of perovskite films, and the weak anchoring ability of phosphate groups toward the NiO _x substrate appears to promote the formation of dimers, trimers, and higher-order oligomers, resulting in molecular accumulation. Herein, a novel technique is proposed to combine Me-4PACz with different thiol molecules to modify the buried interface of PSCs. Molecular dynamics simulations and infrared scattering-type scanning near-field optical microscopy (IR s-SNOM) results show that co-depositing Me-4PACz with thiol molecules forms hybrid SAMs that densely and uniformly cover the NiO _x surface. The island-like structure of the hybrid SAMs serves as a template for forming the perovskite bulk heterojunction composed of interpenetrating networks of MA-rich and FA-rich domains, enabling efficient charge generation and suppressed bimolecular recombination. Particularly, (3-mercaptopropyl) trimethoxysilane (MPTMS) effectively prevents Me-4PACz aggregation by forming a multi-dentate anchor on the NiO _x surface through hydrolytic condensation of ─OCH₃ groups, while its ─SH groups passivate uncoordinated Pb²⁺ at the perovskite/HTL interface. Consequently, the resulting hybrid SAMs-modified PSC achieve a champion photoelectric conversion efficiency (PCE) of 25.4% and demonstrated better operational stability.

The implementation of a dual interfacial passivation approach through thermal annealing with 2,6-pyridinedicarboxylic acid chloride (PAC) successfully coordinated the undercoordinated Pb²⁺ and I⁻ ions in perovskite crystals. This process substantially suppressed defect state density in the material system while simultaneously improving energy level alignment and promoting efficient charge carrier extraction.

Abstract

The rapid crystallization process of perovskite produces a large number of defects that remain a critical factor that disturbs the performance of perovskite solar cells (PSCs). In this research, these challenges are mitigated by introducing multifunctional 2,6-pyridinedicarboxylic acid chloride (PAC) as an additive into perovskite. During the thermal annealing process, the predominant accumulation of PAC occurs at the upper and buried interfaces of perovskite film. PAC possesses multiple passivating sites that facilitate the anchoring of lead and iodine defects, thereby enhancing the quality of the perovskite material across both its dual interfaces and grain boundaries. With this unique property, combined with the advantages of enhanced crystallization, reduced non-radiative recombination, boosted charge carrier mobility, and optimal energy level alignment, the PSC achieved a power conversion efficiency (PCE) of 25.60% and maintained more than 90% efficiency after 3000 h under one solar equivalent light and more than 90% efficiency after 1400 h under dark and high temperature (85 °C). The dual interface passivation strategy provides a sustainable solution to both stability and environmental challenges for the commercialization of perovskite solar cells.

A fluorinated pyrrolidine compound strengthens the lattice bonds in formamidinium (FA)-based perovskites, mitigating phase segregation and device degradation. The resulting 1D/3D heterojunction further enhances phase stability and effectively blocks ion migration channels. Perovskite solar cells achieve enhanced efficiencies, reaching 25.39% (rigid) and 24.26% (flexible), and maintain 90% of their initial performance during maximum power point tracking for over 350 hours under continuous illumination.

Abstract

The unavoidable migration of organic cation within formamidinium (FA)-based mixed halide perovskite leads to severe phase segregation and device degradation. The intrinsic weak chemical bond between organic cation and [PbI₆]⁴⁻ octahedra can easily break during device operation, resulting in the formation of cation vacancies and undesirable structural transformation. In this work, a pyrrolidine compound is incorporated, with a strong electron-withdrawing fluorine substitution, which strengthened the lattice bond between organic cation and [PbI₆]⁴⁻ octahedra. Meanwhile, the 1D/3D heterojunction films are also achieved due to the chemical reaction between PbI₂ and pyrrolidine, successfully constructing a new 1D perovskite such as PYFPbI₃. The resultant hetero-perovskite films retained their photoactive-α phase even after eight days of ambient exposure, demonstrating superior phase stability without any post-encapsulation. More importantly, the ion-migration channels inside the perovskite lattice are effectively blocked by 1D/3D heterojunctions. The resultant rigid and flexible solar cells exhibited an enhanced power conversion efficiency (PCE) from the initial 24.48% to 25.39%, as well as 23.86% to 24.26%, respectively, which are among the highest records in 1D/3D-based works. Furthermore, the unencapsulated devices retained 90% of their initial PCE during maximum power point tracking for over 350 hours under continuous illuminations.

A multifunctional Lewis base cyanoacetohydrazide (CAH) is introduced to synergistically regulate crystallization and phase distribution in 2D/3D tin perovskites through dual coordination with Sn²⁺ ions, effectively reducing defect density and low-dimensional phase formation while enhancing carrier transport. The optimized PSCs achieve a remarkable power conversion efficiency (PCE) of 15.06% with excellent stability, representing an important advancement in lead-free photovoltaics.

Abstract

Tin perovskite solar cells (PSCs) have garnered considerable attention as promising alternatives to lead PSCs due to their lower toxicity and outstanding optoelectronic properties. However, their efficiency and stability, particularly in 2D/3D tin PSCs, are usually hindered by high defect densities and inefficient carrier transport. In this study, a small-molecule Lewis base with multiple functional groups-cyanoacetohydrazide (CAH) is employed to mitigate defects and enhance charge transport in 2D/3D tin PSCs. It is revealed that the carbonyl, amine, and cyano groups in CAH form strong chemical bonds with Sn²⁺ ions, resulting in synergetic coordination effects. Moreover, the strong interaction between CAH and tin perovskite effectively regulates the crystallization process of perovskite film, resulting in a high-quality tin perovskite film with enhanced crystallinity, reduced defect density, and a modulated 2D/3D phase distribution. As a result, the optimized 2D/3D tin PSCs achieve a remarkable power conversion efficiency of 15.06%, marking one of the highest values for 2D/3D tin PSCs. Furthermore, the optimized devices exhibit outstanding stability, retaining 95% of their initial performance after 2000 h of storage in a nitrogen atmosphere.

A short-chain surfactant with a stable conformation is incorporated into SnO₂ colloidal nanoparticles to establish a strong aggregation barrier and ensure uniform deposition of SnO₂ electron transport layer, resulting in a highly stable perovskite solar cell with a power conversion efficiency of 24.12% and an open-circuit voltage of 1.19 V.

Abstract

Uncontrolled deposition of tin oxide (SnO₂ ) colloidal nanoparticles and perovskite precursors poses challenges for improving the efficiency and stability of perovskite solar cells (PSCs). Modifying the electron transport layer (ETL) can both enhance its own performance and influence the crystallization kinetics of the upper perovskite layer. This study incorporates chain-like surfactants with spatially opposite charges for ETL modification. It is found that molecular conformational changes induced by the flexibility of the carbon chain lead to the collapse of the urchin-like structure, impacting the passivation effect and SnO₂ deposition. Due to the more stable conformation of short-chain surfactant, the fully extended carbon chains in the SnO₂ micelles form a stable urchin-like structure, establishing a stronger aggregation barrier that ensures uniform deposition. The ordered distribution of molecules in the ETL allows functional groups to be fully exposed on the ETL surface and facilitates interlayer modification. This approach enhances passivation across layers, alleviates interfacial tensile stress, promotes interlayer contact, and extends the processing window of perovskite, thereby ensuring the high-performance PSCs. Ultimately, an optimized ETL substrate strategy increases PSC device efficiency from 22.21% to 24.12%, and greatly improves the stability of the unencapsulated device under various conditions, providing a new option for ETL modification engineering.

Diluted heterojunctions are employed to increase the structure order in the layer-by-layer fabricated solar cells and polymeric diluent is found superior that the small molecular diluent, creating OSC having dual fibrils with significantly increased absorption and reduced charge recombination to realize an efficiency of 21.0% (certified value of 20.25%).

Abstract

As an exitonic photovoltaic device, organic solar cells (OSCs) consist of electron donating and accepting components in their photoactive layer, in which the molecular interactions between donor and acceptor can significantly affect the nanoscale morphology as well as the photovoltaic performance of OSCs. In this work, by diluting electron donor with electron acceptor having opposite electrostatic potentials to promote the structural order via strengthened intermolecular interactions, this study shows that polymeric diluent is more effective due to its long-ranged conjugated backbone compared with small molecular diluent. The ternary heterojunction made of C5-16:L8-BO binary acceptors diluted with D18 shows the strongest structural order, benefiting from the strong interactions between L8-BO and C5-16. The enhanced structural order within the photoactive layer prepared by layer-by-layer deposition of the diluted p-type and n-type heterojunctions contributes to enhanced light absorption, improved charge transport, and inhibited charge recombination. As the result, OSC based on D18 (PY-IT diluted)/L8-BO:C5-16 (D18 diluted) having donor and acceptor dual fibrils obtains an unprecedented power conversion efficiency of 21.0% (certified value of 20.25%), which is one of the highest certified PCE up to date.

The TOC illustration depicts asymmetric BDTF-CA2O seed crystals (left) harnessing low nucleation barrier and strong crystallinity to facilitate PM6 crystallization. The module's J–V curve (right) highlights the transition from small-area cells to industrial-scale modules, emphasizing the seed crystal strategy's role in achieving uniform morphology and record efficiencies.

Abstract

Organic solar cells now surpass 20% efficiency in small-area devices, but the use of chloroform as a solvent poses industrial scalability challenges because of its limited ability of uniform film formation and toxicity. High-boiling, non-halogenated solvents are being studied as alternatives, but their low solubility and slow evaporation complicate crystallization process. Here, the study introduces a seed crystal strategy by incorporating oligo (ethylene glycol)-modified small-molecule donors to optimize the nucleation and crystallization. The asymmetric BDTF-CA2O molecule, which combines the strong crystallinity of rodanine group and the low nucleation barrier of oligo (ethylene glycol) chain, significantly promotes the crystallization of the polymer donor PM6. Moreover, BDTF-CA2O effectively suppresses excessive phase separation, and optimizes vertical distribution, resulting in enhanced exciton extraction, balanced carrier transport, and reduced recombination losses. Small-area toluene-processed devices achieve a power conversion efficiency of 19.67%. In the realm of large-area organic solar cell modules, this strategy leads to a record active area efficiency of 17.68% and aperture area efficiency of 16.80% (certified at 16.26%), which is the highest reported for organic solar cell modules >10 cm² to date. These achievements highlight the potential of the seed crystal strategy for large-scale production of efficient, large-area organic solar cell modules.

Expanding the sunlight harvesting spectrum while concurrently minimizing energy loss is crucial for high-performance OSCs. Herein, eC9, a nonfullerene acceptor with a narrower bandgap is introduced, as the guest component into the D18:AQx-2F binary system. This ternary strategy resulted in a broadened absorption window, enhanced crystallization, and reduced nonradiative loss, leading to a record efficiency of 20.6% with simultaneous enhancement in V _OC, J _SC, and FF.

Abstract

Simultaneously mitigating both photovoltage and photocurrent losses is crucial for organic solar cells (OSCs) to approach the Shockley–Queisser limit of ideal efficiency. Incorporating a narrower bandgap nonfullerene acceptor (NFA) as a guest component into the host donor:NFA system broadens the absorption spectrum. However, this can also increase the nonradiative decay rate according to the energy-gap law. In this work, ternary OSCs are constructed by combining a narrow bandgap AQx-2F (as host NFA) with a lower bandgap eC9 (as guest NFA), significantly enhancing photocurrent generation without compromising photovoltage. The addition of eC9 acts as a crystallization inducer, extending the crystallization period and increasing the ordered packing distance. This leads to suppressed trap states, elevated dielectric constant, prolonged exciton lifetime, balanced hole/electron transport, and reduced recombination loss. Consequently, the optimized D18:AQx-2F:eC9 ternary OSCs achieve a champion power conversion efficiency (PCE) of 20.6% with a high open-circuit voltage of 0.937 V, a short-circuit current density of 27.2 mA cm⁻² and a fill factor of 80.8%, as validated by an independently certified PCE of 20.0%, establishing a new benchmark for bulk heterojunction OSCs. This work demonstrates an effective method to simultaneously mitigate photovoltage and photocurrent losses, paving the way for high-performance OSCs.

The chelating molecule (CB-PA) serves as both a top-interface molecular bridge and a void-filler to improve the buried interface quality and promote carrier extraction, leading to a high efficiency of 25.27% and superior stability for inverted MA-free perovskite solar cells.

Abstract

Self-assembled monolayers (SAMs) as hole-collecting materials have made remarkable progress in inverted perovskite solar cells (PSCs). However, the incomplete coverage of SAMs and the non-intimate interface contact between perovskite/SAMs usually cause inferior interface characteristics and significant energy losses at the heterojunction interface. Herein, a post-assembled chelating molecular bridge strategy using 5-(9H-carbazol-9-yl)isophthalicacid (CB-PA) is developed to modify the perovskite/SAMs buried interface. It is found that CB-PA can be chemically coupled with MeO-2PACz through π–π stacking between carbazole groups, and chelate with perovskite by forming double C═O···Pb bonds, thus constructing a bridge-connected interface to promote carrier extraction. Simultaneously, the post-assembled CB-PA can fill the voids of MeO-2PACz to form dense hybrid SAMs, resulting in uniform surface potential and improved interface contact. Moreover, CB-PA treatment also tends to induce the oriented crystallization of perovskite films, passivate interface defects, and release lattice stress at the buried interface. Consequently, the CB-PA-based inverted PSCs achieve a champion efficiency of 25.27% with superior operational stability, retaining ≈94% of their initial efficiency after maximum power point (MPP) tracking (65 °C) for 1000 h with ISOS-L-2I protocol. This work provides an innovative strategy to address the buried interface challenges for high-performance inverted PSCs.

By optimizing building blocks and linking modes, a dimeric acceptor, named DY-FL, is innovatively designed and synthesized. Benefiting from the efficient molecular design strategy, DY-FL-based binary OSCs rendered an efficiency of 19.78%. Importantly, DY-FL-based devices showcased significantly enhanced photo/thermal stability in comparison to small molecule acceptor-based OSCs.

Abstract

The development of organic solar cells (OSCs) with high efficiency and stability is highly desirable to facilitate its commercial applications. Although dimeric acceptors with distinctive advantages have been widely studied, high-performance binary OSCs based on such molecules have rarely been achieved. In this work, a new dimeric acceptor (DY-FL) is constructed by simultaneously optimizing the linking sites and units, as well as the building blocks. Thanks to the effective molecular design, DY-FL provides improved molecular stacking for fibrous morphology with favorable exciton/charge dynamics. Consequently, DY-FL-based binary OSCs render a superior power conversion efficiency (PCE) of 19.78%, representing a record-breaking efficiency for binary OSCs based on dimeric acceptors. Importantly, DY-FL-based devices display significantly enhanced operational stability under external stimuli such as light and heat, in comparison to their small molecule acceptor (Y-F)-based counterpart. These findings highlight the significance of building blocks and linking modes, providing insight into the effective molecular design strategy of dimeric acceptors for state-of-the-art OSCs.

By adopting a bimolecular synergistic passivation strategy, it is feasible to achieve micro- and nano-structural modulation of the perovskite surface, thereby passivating surface defects, regulating interface energy levels, and enhancing the interface electric field. This approach maximizes the reduction of nonradiative recombination at the perovskite/C₆₀ interface and demonstrates universal applicability across perovskite/C₆₀ interfaces with different bandgaps.

Abstract

Although p-i-n type inverted perovskite solar cells (PSCs) achieve excellent photoelectric efficiencies, the nonradiative recombination at the perovskite/C₆₀ interface is still the key factor affecting the overall efficiency of p-i-n PSCs. Herein, a synergistic passivation strategy (meta-fluoro-phenylethylammonium iodide and piperazine iodide) is developed to modify the perovskite/C₆₀ interface in p-i-n PSCs. This strategy facilitates in situ reconstruction of the perovskite film to obtain a smooth and flat perovskite surface. Furthermore, the two molecules work synergistically to passivate surface defects, adjust the interface energy levels, and bolster the interface electric field, all of which reduce the nonradiative recombination losses at the perovskite/C₆₀ interface. The optimal PSCs adopting this strategy achieve a power conversion efficiency of 25.85%. (certified value of 25.22%). After operating at the maximum power point for 1000 h, the 95% initial efficiency can be maintained. Furthermore, this process is universally applicable and scalable.

This study introduces an in situ internal encapsulation strategy by integrating cross-linkable p-type small molecules into the antisolvent to construct a highly hole-selective, transparent, and robust passivation contact. The 1.65 eV n–i–p PSC achieves a 19.8% PCE, with better thermal, UV, and operational stabilities, and a bifaciality of 101.4%, alongside a 29.2% certified PCE tandem cell.

Abstract

The optically deficient and intrinsically unstable hole transport layer (HTL) is the Achilles’ heel of n–i–p perovskite/silicon tandems. Here, a minimalist transparent hole-selective contact is developed without additional HTL by simply integrating cross-linkable p-type small molecules into antisolvent. This strategy not only improves the perovskite crystallinity, shields the perovskite from external stressors, and suppresses interfacial mass exchange, but also provides efficient defect passivation and favorable band alignment via the formation of graded heterojunction. Consequently, the corresponding 1.65 eV perovskite solar cell achieves a stabilized efficiency of 19.6%, alongside significantly improved thermal, ultraviolet, and operation stabilities. Furthermore, leveraging its outstanding transparency, a bifacial single-junction device is showcased achieving a record bifaciality of 101.4%, and a monolithic perovskite/silicon tandem boasting a certified efficiency of 29.2% for 1.04 cm², which represents the highest certified efficiency achieved for n–i–p perovskite/silicon tandems. The demonstration of efficient and stable minimalist hole-selective contacts encourages the tandem community to reevaluate the n–i–p structure, with the goal of harnessing the high open-circuit voltage of single-junction n–i–p PSCs.

Linking-site engineering, used to graft two or more monomers, are crucial for achieving high-performance Y-series giant molecule acceptors (Y-GMAs). However, the reported Y-GMAs all use a single-typed linking site, making it difficult to finely-tune their optoelectronic properties. Herein, we develop a non-fully conjugated Y-GMA (named 2Y-we), with hybrid linking sites at the wing and end-group of monomers, to combine the respective advantages of the wing and end-group site linked counterparts. Compared to its parental monomer, 2Y-we shows different intermolecular interaction, crystallinity, packing, and glass transition temperature, allowing optimized active layer morphology (including appropriate phase separation and ordered molecular packing) and stability. Consequently, the D18/2Y-we-based organic solar cells (OSCs) obtain an improved power-conversion-efficiency (PCE) of 17.4% with both higher open-circuit voltage (VOC) and short-circuit current density (JSC), due to the reduced energy loss and efficient exciton dissociation. Inspired by its high VOC×JSC, 2Y-we is introduced into D18:L8-BO to fabricate ternary devices. Thanks to the further optimized morphology and improved charge transport, the ternary OSCs achieve a superior PCE of 19.9%, which is the highest value among the reported non-fully conjugated Y-GMAs. Our developed hybrid linking-site engineering for constructing high-performance Y-GMAs offers an approach to boost device efficiency.

Click chemistry has been used to synthesize a non-ionic cathode interlayer (PDIBr-TOT). The dominant face-on orientation arising from the bulky and extended side chains affords a solar cell efficiency of 19.52 %, out-performing typical self-doping interlayers. Furthermore, the weak electron-donating side chains in the PDIBr-TOT interlayers remarkably enhance the device stability.

Abstract

Electron transport properties of cathode interlayers are crucial to high-performance organic solar cells (OSCs). We propose a novel approach to enhance electron transport of cathode interlayers through controlling a preferential face-on molecular orientation of non-ionic perylene-diimide- (PDI) based cathode interlayers with restricted n-doping effects. 1-(2,5,8-trioxadec-10-yl)-1,2,3-triazole (TOT) units as bulky and extended side chains were incorporated into brominated-PDIs via click chemistry to yield PDIBr-TOT. TOT side chains impart PDI-based interlayers with a dominant face-on orientation, meanwhile leading to a negligible doping effect due to their weak electron-donating properties. Impressively, at a slight doping level, higher electron mobility is gained through efficient vertical charge transport channels built by preferred face-on molecular orientations of PDIBr-TOT, beating the results acquired through strong doping effects of traditional PDIBr−N with an edge-on orientation. Thus, PDIBr-TOT can suppress exciton recombination and lower the surface energies for good contact with active layers, consequently leading to increases in fill factor and short-circuit current. Integrating PDIBr-TOT with various active layers, a remarkable efficiency of 19.52 % is obtained. Moreover, device stability is enhanced by restrained doping effects. Modulating face-on orientations of cathode interlayers prescribed here will encourage further innovative designs of high-performance cathode interlayers towards OSC advances.

Wide-band gap perovskite with high Br content features rapid crystallization, resulting in poor film quality due to the uncontrolled intermediate phases. However, a diammonium salt additive can improve film uniformity and crystallization of perovskite effectively, reducing phase segregation and voltage loss in perovskite-organic tandem solar cells.

Abstract

Wide-band gap perovskite with adjustable band gaps can be integrated with organic solar cells to form tandem solar cells (TSCs), thereby surpassing the Shockley–Queisser limit. However, increasing Br content to elevate the band gap above 1.8 eV complicates crystallization, leading to inferior film quality and defects due to the unmanageable evolution of intermediate phases. Surface passivation improves crystallization but hard to moderate the inhomogeneous component distributions and defects in the bulk phase. Here, we introduce a diammonium salt as an additive to regulate the homogeneity and crystallization of perovskite film, eliminating the low-dimensional intermediate phase for orientated crystallization of 1.85 eV perovskite, resulting in efficient wide-band gap perovskite solar cells with an impressive open-circuit voltage (V _oc) of 1.379 V and operational stability remaining 85 % of their initial efficiency after illumination for 1200 h. Furthermore, perovskite-organic TSCs achieve a champion power conversion efficiency of 24.03 % and a high V _oc of 2.108 V, one of the highest V _oc for perovskite-organic TSCs.

A strategy was proposed to weaken the interaction between solvents and perovskite precursors through halogen ions. This leads to the improved efficiency of the optimized screen-printed device and mini-module to 21.8 % (0.05 cm²) and 18.95 % (12.6 cm²), respectively. This work opens a new avenue to improve the performance of screen-printed PSCs.

Abstract

Screen printing has emerged as a leading candidate for industrial-scale fabrication of perovskite photovoltaics. However, strong solvent-solute interaction in conventional formulations accelerates the preferential crystallization of perovskites at points, hindering the progressive phase evolution from point to line to plane. In this work, we introduced halogen ions to weaken solvent-solute interactions, achieving the reduced Pb⋅⋅⋅O coordination strength counterbalanced by enhanced Pb−I bonding interactions. This weakened interaction delays formamidinium iodide participation in rapid phase transitions to α-formamidinium lead iodide, enabling controlled crystallization kinetics. The optimized screen-printed perovskite solar cells demonstrate remarkable power conversion efficiencies (PCE) of 21.8 % for 0.05 cm² devices and 18.95 % for 5 cm×5 cm mini-modules (active area: 12.60 cm²). Furthermore, this strategy exhibits broad process compatibility, achieving 23–24 % PCEs for both blade-coating and spin-coating devices fabricated under ambient conditions (25–30 °C, 35–50 % relative humidity). These breakthroughs highlight the universal potential of coordination engineering for scalable perovskite photovoltaics.

A synergistic modulation strategy was proposed of perovskite crystallization and the defects at grain boundaries (GBs) and interface by using a novel carbonyl functionalized spacer cation. By this synergetic strategy, improved crystallization, reduced defect density, released residual stress and minimized carrier nonradiative recombination losses were accomplished simultaneously. The inverted devices delivered a champion PCE of 25.77 %.

Abstract

The inverted cesium/formamidinium (CsFA)-based methylammonium-free perovskite solar cells possess great potential in simultaneously realizing high power conversion efficiency (PCE) and excellent stability. However, the uncontrollable crystallization process and poor film quality hinder further enhancement of photovoltaic performance and operational stability. Herein, we propose a synergistic modulation strategy of perovskite crystallization and the defects at grain boundaries (GBs) and interface by using a novel carbonyl functionalized spacer cation. L-Alanine benzyl ester hydrochloride (L-ABEHCl) containing carbonyl functionalized ammonium cation is incorporated into perovskite precursor solution, increasing the nucleation rate and reducing the crystal growth rate because of its strong interaction with precursor components, leading to increased grain size and crystallinity. No 2D perovskite is formed for L-ABEHCl as additive whereas 2D perovskite is formed upon L-ABEHCl post-treatment. It is revealed that FA⁺ and Cs⁺ in precursor solution suppress the formation of 2D perovskite. As a result, the L-ABEHCl passivates the defects at GBs in the form of organic salts and passivates interface defects in the form of 2D perovskite. Due to minimized carrier nonradiative recombination losses, the inverted devices using synergistic modulation strategy achieve a maximum PCE of 25.77 % (certified stabilized PCE of 25.59 %), which is one of the highest PCEs ever reported for the devices based on vacuum flash evaporation method. The unencapsulated target device maintains 90.85 % of its initial PCE after 2300 h of continuous maximum power point tracking, among the most excellent stabilities accomplished by inverted devices.

Three volatile imide additives with large dipole moments which improved the performance of the OSCs device by manipulating the crystallization process of the acceptor were reported. These additives could induce the acceptor to first nucleate and then grow, forming high-quality acceptor domains and improving charge transport. One of the highest power conversion efficiencies of 19.04% was achieved for D18:L8-BO devices treated with pClPA.

Abstract

Large dipole moment additives have strong interactions with the host materials, which can optimize morphology and improve the photovoltaic performance of organic solar cells (OSCs). However, these additives are difficult to remove due to their strong intermolecular interactions, which may impair stability. Developing volatile additives with large dipole moments is challenging. Herein, we first report volatile imide additives that could effectively improve the performance of OSCs through morphology modification. Three additives N-(o-chlorophenyl)phthalimide (oClPA), N-(m-chlorophenyl)phthalimide (mClPA), and N-(p-chlorophenyl)phthalimide (pClPA) were screened to investigate the effort of positional isomerization on molecular configuration and interaction. These additives (ClPAs) have larger dipole moments (2.0664 Debye for oClPA, 4.2361 Debye for mClPA, and 4.7896 Debye for pClPA) compared to reported solid additives. In contrast to traditional simultaneous nucleation and crystal growth, ClPAs could induce the acceptor to nucleate first and then grow, which contributes to forming high-quality acceptor domains with better crystallinity. To our knowledge, this unique film formation kinetics was reported first. The power conversion efficiency (PCE) of OSCs based on PM6:BTP-eC9 treated with pClPA was improved from 16.13 % to 18.58 %. Additive pClPA also performed well in PM6:L8-BO, PM6:Y6, and D18:L8-BO systems, and a high PCE of 19.04 % was achieved. Our results indicate using imide unit to construct solid additives is a simple and effective strategy, and the positional isomerization of halogen atom also has a large effect on the photovoltaic performance.

Bis-sulfonimide (BSI), distinguished by multiple d-pπ bonds rather than typical p-pπ bonds, is unprecedently introduced as an adaptable electron-withdrawing motif to construct interlayer materials for organic solar cells (OSCs). The unique conformational and electronic structure of BSI imparts excellent thickness tolerance and universal applicability to the interlayer materials, leading to 19.80 % efficiency OSCs with good operational stability.

Abstract

Herein, bis-sulfonimide (BSI), characterized by multiple d-pπ bonds rather than typical p-pπ bonds, is unprecedently utilized as a general and extendable building block to develop a series of multifunctional cathode interlayer materials (CIMs) for organic solar cells (OSCs). An illustrative CIM, BSIz-TT-PDI, demonstrates favorable alcohol processability, superior work function tunability, appropriate energy levels, strong self-doping effect, and decent crystallinity. These attributes contribute to its high conductivity exceeding 5×10⁻³ S/cm, as well as precise optimization of the interfacial connection between the active layer and metal cathode. Therefore, BSIz-TT-PDI-based OSCs delivers an outstanding efficiency of 18.08 % using PM6:Y6 active layer while retaining 84 % of its initial performance after tracking at the maximum power point under continuous illumination for 1100 hours. Additionally, the devices maintain over 94 % of the optimal performance across a film thickness range of BSIz-TT-PDI from 5 to 90 nm. Moreover, BSIz-TT-PDI exhibits high compatibility with various active layers, enabling a record efficiency of 19.80 % with the PM6:BTP-eC9:L8-BO active layer. This work not only introduces a new library of water/alcohol-soluble n-type semiconductors containing BSI, while also pioneers the creation of thickness-insensitive CIMs for stable and efficient OSCs by integrating electron-withdrawing components with d-pπ bonds.

By novel molecular design, a dimerized acceptor (DY-FBrL) was synthesized. DY-FBrL-based rigid devices render an efficiency of 18.75 % and crack-onset strain (COS) of 18.54 %. A polymerized acceptor (PDY-FL) was prepared via polymerization of DY-FBrL. Compared to DY-FBrL, PDY-FL-based rigid devices display a higher COS of 23.45 % but a lower efficiency of 14.13 %. Importantly, intrinsically-stretchable devices based on DY-FBrL and PDY-FL exhibit excellent device stretchability.

Abstract

Intrinsically stretchable organic solar cells (IS-OSCs) are emerging as promising candidates for powering next-generation wearable electronics. However, developing molecular design strategies to achieve both high efficiency and mechanical robustness in IS-OSCs remains a significant challenge. In this work, we present a novel approach by synthesizing a dimerized electron acceptor (DY-FBrL) that enables rigid OSCs with a high power conversion efficiency (PCE) of 18.75 % and a crack-onset strain (COS) of 18.54 %. The enhanced PCE and stretchability of DY-FBrL-based devices are attributed to its extended π-conjugated backbone and elongated side chains. Furthermore, we introduce an innovative polymerized acceptor (PDY-FL), synthesized via the polymerization of DY-FBrL. While PDY-FL-based devices exhibit a slightly lower PCE of 14.13 %, they achieve a significantly higher COS of 23.45 %, representing one of the highest PCEs reported for polymerized acceptors containing only flexible linkers. Consequently, IS-OSCs fabricated using DY-FBrL and PDY-FL achieve notable PCEs of 14.31 % and 11.61 %, respectively. Additionally, the device stretchability improves progressively from Y6 (strain at PCE_80%=11 %), to DY-FBrL (strain at PCE_80%=23 %), and PDY-FL (strain at PCE_80%=31 %). This study presents a promising molecular design strategy for tailoring electron acceptor structures, offering a new pathway to develop high-performance IS-OSCs with enhanced mechanical properties.

Abstract

The precise regulation of self-assembled monolayer (SAM) distribution and interfacial modification is pivotal for advancing the performance of p-i-n inverted perovskite solar cells (PSCs). Here, a new co-assembly material, 4-(aminomethyl)-N,N-diphenylaniline iodide (TPAI), is developed to make SAM orderly assembled. Density functional theory (DFT) calculation and sum frequency generation (SFG) spectroscopy reveal that TPAI binds with SAM via π-π interactions, effectively suppressing SAM aggregation and enhancing the orderliness of self-assembly. Further characterization by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) demonstrates that ─NH₃ group in TPAI coordinates with undercoordinated Pb²⁺ to passivate defects of cesium lead triiodide (CsPbI₃) film. The TPAI modification creates a defect-minimized buried interface with optimized energy alignment, significantly improving hole extraction and transport kinetics. Consequently, the TPAI-treated CsPbI₃ PSCs achieve a high power conversion efficiency (PCE) of 21.60%, the highest reported value for inverted CsPbI₃ PSCs, maintaining 96.71% initial PCE after tracking at maximum power point (MPP) for 1400 h. This work provides a molecular-level strategy for interfacial engineering, advancing the development of efficient and durable perovskite photovoltaics.

The operational perovskite/organic tandem solar cells are subjected to light irradiation and driven by a higher bias voltage than single-junction solar cells, posing a severe challenge to their stabilities. Light irradiation can trigger halide phase segregation in the perovskite subcell, exacerbated under higher bias voltage through electron–phonon coupling. To address this, dimethylammonium ion (DMA+) incorporation delays perovskite crystallization by forming an intermediate phase, enhancing crystallinity, and reducing lattice structural defects. DMA+ with a larger ionic radius entering the A-site of lattice tilts the [PbX6]4- (X: I or Br) octahedral, enlarging the perovskite bandgap, shortening Pb–I bonds, and reinforcing the lattice. This mitigates halide escaping from the lattice and subsequent ion migration. Phase segregation in the perovskite subcell is significantly suppressed under high-power irradiation and bias voltage. Consequently, the perovskite subcell exhibits increased and stable quasi-Fermi-level splitting values, delivering a high open-circuit voltage of 1.34 V. Notably, 0.062-cm2 and 1.004-cm2 perovskite/organic tandem solar cells achieved remarkable efficiencies of 26.15% (certified of 25.34%) and 24.87%, respectively, exhibiting excellent operational stability of T90 ~ 1350 h.

Nature Communications, Published online: 20 February 2025; doi:10.1038/s41467-025-57118-9