Chen Weijie

Publication date: 20 August 2025

Source: Joule, Volume 9, Issue 8

Author(s): Jiazhi Meng, Yu Gao, Junnan Hu, Chengcheng Wu, Yuan Li, Si-Wei Zhang, Yuou Chen, Ross A. Kerner, Jing Ma, Yang Shen, Xuan Zhang, Feiyu Kang, Barry P. Rand, Guodan Wei

Nature Energy, Published online: 18 April 2025; doi:10.1038/s41560-025-01760-6

The work highlights the strong morphological optimization capacity of the solid additive DIDOB and elucidates its impact on molecular packing to suppress both bimolecular and geminate recombination in OSCs. As a result, DIDOB not only demonstrates universality in various non-fullerene-based OSCs but also achieves an impressive efficiency of 20.11% with a remarkable fill factor of 81.8% in the D18:PM6:L8-BO-based device.

Abstract

A volatile solid additive strategy, which can effectively optimize the morphology of the photoactive layer with an ideal domain size and purity, has emerged as a promising approach to improve the photovoltaic performance of organic solar cells (OSCs). However, the precise role of solid additives in modulating charge and exciton dynamics, especially the recombination process, remains not fully understand. In this study, a solid additive, 1,4-diiodo-2,5-dimethoxybenzene (DIDOB), is developed to improve the photovoltaic performance of OSCs and conduct a comprehensive investigation into its effect on the charge recombination process. As a result, the PM6:L8-BO-X-based binary OSC processed with DIDOB achieves an excellent efficiency of 19.75% with a remarkable fill factor of 81.9%, owing to the optimal fiber network morphology, tighter and ordered molecular packing, as well as the suppression of both bimolecular and geminate recombination. Notably, the DIDOB exhibits broad universality as an additive in other non-fullerene acceptor-based OSCs. Impressively, the D18:PM6:L8-BO-based ternary device processed with DIDOB yielded an excellent efficiency of 20.11% (certified as 20.03%). This work highlights the effect of the solid additive on the charge recombination process within active layer and provides insights for the further development of OSCs.

A new solvent, trichloroethylene (TCE), is introduced and used as an acceptor processing solvent in layer-by-layer processed devices. The active layer exhibits a higher proportion of transport phases and lower trap-assisted charge recombination. The efficiency of the binary organic solar cell reached 20.05%, with a record-high fill factor of 83%.

Abstract

For spontaneously crystallized organic photovoltaic materials, morphology optimization remains a challenge due to the disparity in crystallinity between the donor and acceptor components. Imperfections in the crystalline phases result in significant trap-assisted recombination, which emerges as a critical factor limiting the fill factor (FF) of organic solar cells (OSCs). Herein, a method is introduced for precise regulation of the acceptor crystallinity, utilizing a novel upper-layer acceptor processing solvent, trichloroethylene (TCE), to improve the state and vertical morphology of the active layer. The TCE solvent synergistically optimizes intermolecular interactions among acceptor molecules and balances the film-forming process, thereby increasing the proportion of transport phases and forming high-speed channels for electron transport, which subsequently reduces trap-assisted charge recombination. As a result, the photovoltaic efficiency of binary organic solar cells reaches 20.05%. More importantly, an unprecedented FF of 83.0% is obtained, representing the highest FF value for OSCs. This facile and effective approach offers a promising means for constructing efficient charge transport networks and fabricating high-efficiency and morphologically stable OSCs.

A pumping rate-controllable strategy regulates nucleation and crystallization in Sn-Pb perovskites during vacuum-flash-assisted solution processing. This approach enables additive-free, antisolvent-free fabrication of high-quality films, achieving >21% and >19% efficiency for 0.08 and 1 cm² devices, respectively, with uniformity over 6 × 6 cm². It also delivers 27.5% efficiency for all-perovskite tandem cells, ensuring scalability and reliability.

Abstract

The rapid crystallization of mixed tin-lead (Sn-Pb) perovskites and their dependence on antisolvent processes limit the development of large-area Sn-Pb perovskite solar cells (PSCs). Vacuum-flash-assisted solution processing (VASP) has emerged as a promising technique for large-scale fabrication. However, achieving consistent control over crystallization parameters remains a limitation. To address this, a pumping rate-controllable strategy is introduced, fitted from cavity pressure and time, to control nucleation and crystallization in Sn-Pb perovskite films. By tuning the pressure rate, the solvent volatilization rate of the perovskite wet film is optimized, enabling controlled nucleation and crystallization dynamics. This allows for the scalable fabrication of high-quality FA_0.7MA_0.3Pb_0.5Sn_0.5I₃ films without additives to aid crystallization, achieving power conversion efficiencies (PCEs) exceeding 21% and 19% for Sn-Pb PSCs at 0.08 cm² and 1 cm², respectively, the additives-free and antisolvent-free highest records. This further demonstrates that the uniformity and reproducibility of pumping rate control on a large 6 × 6 cm² substrate. The approach is also applicable to wide bandgap PSCs, normal bandgap PSCs, and all-perovskite tandem solar cells, delivering a PCE >27% for the antisolvent-free and additive-free tandem device. This work establishes a scalable and versatile approach for developing large-area Sn-Pb and all-perovskite tandem devices, advancing the field toward practical applications.

A doping strategy of incorporating Bis(trifluoroacetoxy)iodo)benzene (BTFIB) additive in 1.67 eV WBG perovskite precursor has been proposed to passivate uncoordinated lead ions and iodide vacancies and retard the crystallization of perovskite. Finally, BTFIB-based perovskite solar cells yielded a champion efficiency of 23.05% (certified 22.21%) and enabled a four-terminal perovskite/Si tandem cell with a PCE of 31.20% and excellent long-term stability.

Abstract

Wide-bandgap (WBG) perovskite solar cells (PSCs, E_g > 1.6 eV), serving as the top cell in perovskite/silicon tandem solar cells (PSTSCs), play an indispensable role in absorbing high energy photons and increasing overall efficiency. However, WBG PSCs often suffer from severe light-induced phase segregation and significant non-radiative recombination losses due to uncontrolled rapid crystallization. Here, polyfluoride molecular additives are designed and incorporated via (diacetoxyiodo)benzene into WBG perovskite, to regulate crystallization process of perovskite films and thereby reduce defects. (Bis(trifluoroacetoxy)iodo)benzene (BTFIB) can passivate uncoordinated lead ions and iodide vacancies, thereby inhibiting phase separation caused by iodide migration and reducing non-radiative recombination loss during charge transport. Moreover, the introduction of BTFIB can effectively moderate the film formation process and confer excellent hydrophobic properties to the films. Consequently, BTFIB-based 1.67 eV-WBG perovskite devices yield a champion efficiency of 23.05% (certified efficiency of 22.21%), enabling a 31.20% efficiency in four-terminal PSTSCs, along with excellent open-circuit voltage of 1.246 V and fill factor of 85.34%. After 2500 h of aging in a glovebox, the device retained 80% of its initial efficiency.

A novel bifacial-iridescent solar cell is developed using an inverse opal perovskite photonic crystal. It exhibited unique iridescent structural colors on both sides and achieved an impressive bifacial equivalent efficiency of 18.00% for small cells and 12.77% for mini-modules.

Abstract

Colorful perovskite solar cells exhibit excellent potential for building-integrated photovoltaics (BIPVs), which increase the utilization of clean power. However, their efficiencies are lower than those of uncolored devices. Moreover, traditional mono-facial colored devices cannot satisfy diverse BIPV scenarios. Here a bifacial iridescent solar cell (BFI-SC) is developed, constructed by inverse opal (IO) perovskite photonic crystals and transparent front and rear electrodes. The developed BFI-SC exhibited bright vivid colors on both sides, which originate from the reflection at the photonic stop band of the IO perovskite photonic crystal. Moreover, this unique IO photonic crystal decreased the interfacial Fresnel reflection and generated a slow-photon effect, which increases the material light absorption and utilization to obtain high efficiency. Furthermore, the BFI-SC can harvest light from both sides, considerably enhancing the device efficiency. Thus, the BFI-SC achieved an impressive bifacial equivalent efficiency (η _eq) of 18.00%, which is the highest value achieved for the reported multicolored (or iridescent) solar cell. A larger-scale BFI-SC module is successfully assembled, achieving a champion η _eq of 12.77%. In addition, another perovskite material with an IO structure and wide-bandgap components exhibited vivid colors on both sides, indicating the universality of this coloring strategy and its independence of the perovskite components.

DAC-AA into SnO₂ colloids favors the crystalline phase and preferential orientation along high-oriented (101) and (200) crystal planes by reducing surface absorption energy and modulating crystal thermodynamics, promoting heating transfer rate in the flexible PEN substrate and favoring perovskite/SnO₂ lattice matching. The f-PSCs fabricated in full-air conditions produce an efficiency of 23.87% and exceptional mechanical stability.

Abstract

Tin (IV) oxide (SnO₂) electron transport layer (ETL) emerges as the most promising n-type semiconductor material for flexible perovskite solar cells (f-PSCs). The (110) facet-dominated SnO₂ colloids are readily created, whereas other best-performing (101) and (200) facets-dominated ones with superior potential in interface modulation and lattice matching remain insufficiently explored. Here water-soluble acryloyloxyethyltrimethyl ammonium chloride-acrylamine (DAC-AA) doping into SnO₂ colloids produces more (101)- and (200)-oriented crystal domains through lowering surface absorption energy and offering additional thermodynamic driving force. Theoretical and experimental analyses corroborate that the grain preference orientation induced by DAC-AA modification strengthens heating transfer rate on the flexible substrate and favors lattice matching of perovskite (100) plane on SnO₂ (101) and (200) facets. Accordingly, the champion f-PSCs on high-oriented SnO₂-DAC-AA ETLs fabricated fully in ambient air conditions achieve the efficiencies of 23.87% and 22.41% with aperture areas of 0.092 and 1 cm². In parallel, the propitious interfacial lattice arrangement attenuates the formation of micro-strain inside perovskite films, maintaining 92.5% of their initial performance after 10 000 bending cycles with a curvature radius of 6 mm.

A gradient electron energy level strategy is constructed to reduce voltage losses in planar HTL-free CsPbI₂Br C-PSCs. This electron extraction optimization enables rapid photogenerated electron extraction and carrier separation, thereby suppressing recombination at the back contact. The resulting PSCs deliver a record V _OC of 1.41 V, a high PCE of 17.42% and a high stability, simultaneously.

Abstract

Carbon-based CsPbI₂Br perovskite solar cells (PSCs) free of a hole-transport layer (HTL) have emerged as promising photovoltaics due to their low processing cost and superior stability. However, the voltage deficit resulting from inefficient carrier extraction causes insufficient power conversion efficiency (PCE), severely hindering their progress. Here, a gradient electron energy level modulation strategy proves effective in reducing voltage losses through the rapid extraction of photogenerated electrons. This process enhances carrier separation/collection and reduces recombination at the back contact, thereby achieving high-performance photovoltaics. It is demonstrated that the front electron extraction, equally critical as the prevailing back perovskite/carbon contact, accounts for the significant contributing factor of voltage deficit in carbon-based HTL-free PSCs. The resulting PSCs deliver a record open-circuit voltage (V _OC) of 1.41 V and a PCE of 17.42% and retain more than 92% of their initial efficiency after 1, 000 h. These results highlight the significant potential of carbon-based HTL-free perovskite photovoltaics.

Herein, through regiospecific bromination on a helical 7H-dibenzo[c,g]carbazole-based SAM (CbzNaph) featuring a stronger dipole, we study the properties related to intrinsic stability, electrostatic potential (ESP) distribution, and changes in the molecular dipole of the derived SAM molecules. Bromination at the chemically inert sites of 7H-dibenzo[c,g]carbazole (JJ26) helps maximize molecular dipole while maintaining superior intrinsic stability. Together with the dense assembly promoted by enhanced intermolecular interactions and synergistic effects of stronger crystallinity, JJ26 efficiently modulates the work function (WF) of indium tin oxide (ITO) and enhances the stability of SAM under external pressure. The OSC device adopting JJ26 demonstrates significantly improved performance, achieving an efficiency of 19.35% along with notably enhanced stability.

Abstract

Halogenated carbazole-derived self-assembled monolayers (SAMs) are promising hole-extraction materials in conventional organic solar cells (OSCs). While halogenation helps optimize the molecular dipole, intermolecular interactions, and energetics of SAM, the highly polarizable carbon-halogen bonds can be reactive and prone to photocleavage depending on their regiochemistry. Herein, we study the regiospecific properties, including the intrinsic stability, electrostatic potential (ESP) distribution, and changes in molecular dipole of the brominated SAM molecules by brominating a helical 7H-dibenzo[c,g]carbazole-based SAM (CbzNaph) featuring a stronger dipole. Additionally, a correlation between the intrinsic molecular stability and the derived SAM surface stability is established to determine the performance and stability of the OSCs. Notably, the bromination at the chemically inert sites of 7H-dibenzo[c,g]carbazole (JJ26) helps maximize molecular dipole while maintaining superior intrinsic stability. Together with dense assembly promoted by the synergistically enhanced intermolecular interactions and crystallinity, JJ26 can efficiently modulate the work function (WF) of indium tin oxide (ITO) and enhance the stability of SAM under external stress. Consequently, the JJ26 derived OSC shows significantly improved performance, achieving an efficiency of 19.35% along with notably enhanced stability. This work shows that the precise modulation of the regiochemistry of SAM molecules is critical for improving their quality and derived device performance.

A small molecule, CNDT, is introduced into the active layer and increases the disorder of electron donor/acceptor interfaces. It enhances the energy of the charge transfer state and leads to an uphill energy barrier for bimolecular recombination, reduces charge recombination rate/ratio and inhibits bimolecular recombination in OSCs. Therefore, D18:L8-BO based OSCs featuring CNDT achieve arecord fill factor of 83.17% and an impressive PCE of 19.80%.

Abstract

The inferior fill factor (FF) is one of main reasons impeding further improvement of power conversion efficiencies (PCEs) in organic solar cells (OSCs). But no theoretical framework for high FFs has been established yet. Herein, an efficient strategy is developed to enhance FFs via introducing a small molecule, CNDT, into active layer to increase electron donor/acceptor interface disorder, raise energy barrier for charge back transfer, and thus reduce bimolecular recombination rate constant (k _rec). CNDTs tend to distribute over donor/acceptor interfaces and disturb molecular stacking of Y6 to deliver more disordered donor/acceptor interfaces but higher crystal quality in the D18:Y6+ blend film, compared to D18:Y6. Altogether, in the D18:Y6+ blend film, a higher energy of charge transfer state magnifies energy barrier for charge recombination to decrease charge recombination rate/ratio and reduce k _rec, inhibiting bimolecular recombination in devices. Therefore, FFs of OSCs are improved from 75.78% (D18:Y6) to 81.13% (D18:Y6+), yielding a higher PCE of 19.45%. Moreover, D18:L8-BO+ based OSCs feature FFs over 83%, a record for OSCs so far. PCE increases subsequently to 19.80%. It demonstrates that increasing interface disorder without sacrificing crystal quality enhances energy barrier of charge recombination and inhibits bimolecular recombination to efficiently improve FFs for higher PCEs.

Molecular geometry plays a crucial role in determining photovoltaic properties of organic semiconductor materials for organic solar cells (OSCs). In this work, we used dichlorine-substituted benzene as the A’ unit in A-DA'D-A type small molecule acceptors (SMAs) and synthesized four isomers of the benzodipyrrole-based SMAs (C-Cl46-Cl, Ɂ-Cl46-Cl, M-Cl46-Cl and S-Cl46-Cl) with C, Ɂ, M, and S molecular geometries, and the effect of the molecular geometry on their photovoltaic performance was studied. We revealed that the molecular geometry influences the physicochemical and photovoltaic properties in three aspects: (1) intrinsic physicochemical properties, including energy levels, absorption and reorganization energy; (2) molecular stacking pattern, which govern the exciton diffusion and charge transport process; and (3) donor-acceptor interaction and miscibility. We found that the C-shaped molecular geometry possesses suitable energy level and absorption range, dense and ordered molecular stacking, and improved donor-acceptor interactions and miscibility. These advantages enable a record-high power conversion efficiency (PCE) of 19.94% (certified as 19.54%) for the binary OSCs based on D18:C-Cl46-Cl active layer. The other shaped SMAs showed weaknesses in different aspects, such as limited absorption of Ɂ-shaped SMA, large reorganization energies and loose molecular stacking of M-shaped SMA, low solubility and strong aggregation of S-shaped SMA.

Developing acceptors geared toward efficient facilely processed OSCs is imperative for widespread commercialization. Herein, an alkyl linearization strategy was adopted to promote compact and face-on molecular stacking, and further vinyl functionalization of alkyl terminals provided additional interaction sites to manifest enhanced π–π stacking of BTP-V6, resulting in record PCEs of 19.2% and 20.1% for as-cast and optimal LBL OSCs, respectively.

Abstract

Developing efficient and stable as-cast organic solar cells (OSCs) is imperative for alleviating costs and complexity for large-scale commercial applications. Nevertheless, achieving the desired double-fibril morphology of active layer through single-step processing is challenging. Herein, two nonfullerene acceptors, namely BTP-N6 and BTP-V6, are designed and synthesized to construct as-cast OSCs by introducing linear alkyl chains adjacent to the pyrrole moiety. The reduction of steric hindrance attributable to linear chains engenders diminished dihedral angles of molecular skeletons, thereby promoting compact and face-on oriented molecular stacking. Moreover, BTP-V6 featuring vinyl-functionalized linear chains manifests additional interaction sites with neighboring molecules to instigate enhanced π–π stacking during rapid film-formation process and engenders the formation of a refined double-fibril network morphology, which facilitates exciton dissociation, bolsters charge carrier transport, and suppresses recombination loss. Consequently, the D18:BTP-V6 based device attained a record-shattering efficiency of 19.2% with a high fill factor (FF) of 80.7%, and also demonstrated robust thermal and shelf stability. Moreover, the meticulously optimized layer-by-layer (LBL) structured devices achieved an excellent efficiency up to 20.1%. This study introduces a viable strategy for alkyl chain modification to fabricate efficient and stable as-cast devices, with the anticipation of expediting the progression toward widespread commercialization of OSCs.

A surface halide substitution strategy is applied to establish function-gradient inorganic perovskite, producing stable chlorine-rich layers atop iodine-rich ones, achieving 21.2% efficiency in unit cells and 19.2% efficiency in modules, resulting in a projected T ₈₀ lifetime of 7.3 years. This makes them among the most stable wide-bandgap perovskite devices.

Abstract

Iodine-rich inorganic perovskites possessing desirable bandgaps as well as high thermal and chemical stability are facing serious issues of low polymorphic stability, whereas chlorine-rich inorganic perovskites hold outstanding thermodynamic stability but suffer from low efficiency. Here, we develop function-gradient inorganic perovskites adopting a surface halide substitution strategy, where a stable chlorine-rich skin protects efficient iodine-rich layers, incorporating high stability of chlorine-rich perovskites with high efficiency of iodine-rich perovskites. This strategy simultaneously passivates surface defects and stabilizes the photoactive polymorphs of perovskite, leading to a power conversion efficiency of 21.2% for unit cells (0.16 cm²) and 19.2% for solar modules (23.9 cm²). Notably, the compositional gradient mitigates light-induced ion migration and enhances resistance to environmental erosion. Thus, our devices exhibit negligible efficiency loss after 1000 h storage in air and 3200 h operation under continuous 1-sun illumination at 40 °C, representing the most stable wide-bandgap perovskite solar cells reported to date.

A fine-grained sub-cell matching model is developed to optimize the series current density of perovskite-organic tandem solar cells (TSCs). Based on the thick organic films strategy, the TSC achieve a remarkable efficiency of 24.31% (certified as 24.00%). A large-area module (18.48 cm²) is further fabricated with an impressive efficiency of 18.54%, which is the first demonstration of perovskite-organic tandem modules.

Abstract

Perovskite-organic tandem solar cells (TSCs) possess significant potential due to their unique features, such as orthogonal processing solvents, tunable bandgap, and infinite molecular designs. However, their device performance is often hindered by the limited series current density, which is constrained by the absorption of the rear organic solar cell (OSC). Here, a fine-grained sub-cell matching model has been developed that enables rapid screening of material combinations based on practical sub-cell device parameters. The model indicates that increasing the thickness of the OSC layer is an effective approach to boost efficiency, while also reducing manufacturing challenges for large-scale production. To mitigate the charge collection issues arising from excessive thickness, a contact passivation technique based on a self-assembled monolayer has been developed, which minimizes non-radiative recombination and reduces the Schottky barrier at the interface, enabling more balanced hole-electron transport. As a result, the thick-film (300 nm) has achieved a record-high efficiency of 18.08% (certified as 17.80%), enhancing the efficiency of TSCs to 24.31% (certified at 24.00%). Furthermore, a large-area tandem photovoltaic module with an efficiency exceeding 18.54% (18.48 cm²) has been demonstrated. To the knowledge, this represents the first module demonstration for perovskite-organic TSCs.

This study elucidates how the molecular orientation of conjugated self-assembled monolayers (SAMs) governs work function (WF) modulation via alignment of the conjugated core with the surface normal. Edge-on-oriented BCZ-1 molecule maximizes vertical dipole moments and achieves dense in-plane coverage, enabling ultrafast hole extraction and minimized recombination. The resultant binary organic photovoltaics achieve a record efficiency of 19.93%, highlighting orientation engineering as a pivotal strategy for high-performance devices.

Abstract

Molecular orientation stands as the quintessential hallmark of conjugated self-assembled monolayers (SAMs), which have recently catalyzed noteworthy advancements in organic photovoltaics (OPVs). Nevertheless, an unambiguous understanding of these directional arrangements and their impact on optoelectronic properties remains elusive. To address this issue, herein three SAMs with representative orientations, i.e., edge-on (BCZ-1), tilt-on (4PACz) and face-on (BCZ-2) are meticulously designed. These orientations have been rigorously validated by sum frequency generation vibrational spectroscopy and first-principles calculations. Remarkably, an unequivocal correlation between the molecular orientation and the device performance is discerned. Particularly, the edge-on oriented BCZ-1 exhibits the largest dipole moment normal to the electrode, accompanied by a dense and uniform coverage. These features collectively contribute to its strongest work function increment for ultra-fast hole extraction and minimum interfacial carrier recombination. As a result, a champion power conversion efficiency of 19.93% is achieved in devices based on BCZ-1 with D18:L8-BO as the active layer, representing one of the highest values reported for binary bulk heterojunction OPVs. Besides, BCZ-1 shows great potential for practical applications due to its superior up-scalability and enhanced device shelf-stability. Overall, this work offers in-depth insights into the orientation behaviors of SAMs, opening new avenues to unlock the efficiency potential of OPVs.

This study addresses a critical challenge in the commercialization of perovskite solar modules by reducing photovoltage loss through the in situ formation of a surface conductive coordination polymer at the surface/interface of the perovskite film.

Abstract

Despite the reported high efficiencies of small-area perovskite photovoltaic cells, the deficiency in large-area modules has impeded the commercialization of perovskite photovoltaics. Enhancing the surface/interface conductivity and carrier-transport in polycrystalline perovskite films presents significant potential for boosting the efficiency of perovskite solar modules (PSMs) by mitigating voltage losses. This is particularly critical for multi-series connected sub-cell modules, where device resistance significantly impacts performance compared to small-area cells. Here, an effective approach is reported for decreasing photovoltage loss through surface/interface modulation of perovskite film with a surface conductive coordination polymer. With post-treatment of meso-tetra pyridine porphyrin on perovskite film, PbI₂ on perovskite film reacts with pyridine units in porphyrins to generate an iso-structural 2D coordination polymer with a layered surface conductivity as high as 1.14 × 10² S m⁻¹, due to the effect of surface structure reconstruction. Modified perovskite film exhibits greatly increased surface/interface conductivity. The champion PSM obtains a record efficiency up to 23.39% (certified 22.63% with an aperture area of 11.42 cm²) featuring only 0.33-volt voltage loss. Such a modification also leads to substantially improved operational device stability.

A general strategy- “interfacial energetics reversal” to reconstruct perovskite energetics that matches well with the upper hole transport layer has been successfully developed, enabling efficient n–i–p perovskite solar cells with nonradiative recombination induced qVoc loss of only 57 meV from the radiative limit.

Abstract

Reducing heterointerface nonradiative recombination is a key challenge for realizing highly efficient perovskite solar cells (PSCs). Motivated by this, a facile strategy is developed via interfacial energetics reversal to functionalize perovskite heterointerface. A surfactant molecule, trichloro[3-(pentafluorophenyl)propyl]silane (TPFS) reverses perovskite surface energetics from intrinsic n-type to p-type, evidently demonstrated by ultraviolet and inverse photoelectron spectroscopies. The reconstructed perovskite surface energetics match well with the upper deposited hole transport layer, realizing an exquisite energy level alignment for accelerating hole extraction across the heterointerface. Meanwhile, TPFS further diminishes surface defect density. As a result, this cooperative strategy leads to greatly minimized nonradiative recombination. PSCs achieve an impressive power conversion efficiency of 25.9% with excellent reproducibility, and a nonradiative recombination-induced qV _oc loss of only 57 meV, which is the smallest reported to date in n-i-p structured PSCs.

The α-FAPbI₃ perovskite, ideal for high-efficiency solar cells, suffers from impurity phases causing defects and instability. Using FAI/MASCN vapors repairs impurities into α-FAPbI₃, enhancing charge transport and morphology. This achieves 26.05% efficiency, with large-area devices (24.52% for 1 cm², 22.35% for 17.1 cm²). Cyclic repair retains 94.3% efficiency after two cycles, significantly boosting device durability.

Abstract

The photoactive α-phase of formamidinium lead iodide perovskite (α-FAPbI₃) is regarded as one of the ideal materials for high-efficiency perovskite solar cells (PSCs) due to its superior optoelectronic properties. However, during the deposition of α-FAPbI₃ perovskite films, the presence of impurity phases, such as PbI₂ and δ-FAPbI₃, can cause the formation of inherent defects, which leads to suboptimal charge transport and extraction properties, as well as inadequate long-term stability in the film's morphology and structure. To address these issues, an impurity phase repair strategy is employed using FAI/MASCN mixed vapors to convert the impurity phases into light-absorbing α-FAPbI₃. Meanwhile, this recrystallization process also facilitates the recovery of its characteristic morphology, thereby improving efficiency and enhancing the durability of PSCs. This approach promotes the PSCs to obtain an efficiency of 26.05% (with a certified efficiency of 25.67%, and steady-state PCE of 25.41%). Additionally, this approach is suitable for the fabrication of large-area devices, obtaining a 1 cm² device with a PCE of 24.52% and a mini-module (with an area of 17.1 cm²) with a PCE of 22.35%. Furthermore, it is found that this strategy enables cyclic repair of aged perovskite films, with the perovskite solar cells retaining ≈ 94.3% of their initial efficiency after two cycles of repair, significantly enhancing the lifetime of the perovskite solar cells.

Nature Materials, Published online: 03 April 2025; doi:10.1038/s41563-025-02199-6

Nature Materials, Published online: 10 April 2025; doi:10.1038/s41563-025-02189-8

Nature Energy, Published online: 07 April 2025; doi:10.1038/s41560-025-01747-3

Nature Energy, Published online: 07 April 2025; doi:10.1038/s41560-025-01746-4

Nature Energy, Published online: 10 April 2025; doi:10.1038/s41560-025-01756-2

Nature, Published online: 08 April 2025; doi:10.1038/s41586-025-08961-9

The perovskite p–n homojunction is constructed via a simple perovskite buried interface engineering. Thanks to the driven force induced by the homojunction, charge carriers are efficiently extracted, and the corresponding perovskite homojunction solar cell achieves a champion efficiency of 25.0%.

Abstract

Constructing a strong p–n junction is an effective strategy to drive the separation of photogenerated charge carriers and boost the photovoltaic performance of solar cells. However, forming p-type and n-type semiconductors in perovskites is not as straightforward as in archetypal Si by doping electron-accepting and electron-donating elements. Here, we observe the transition of p-type to n-type characteristics in a perovskite layer via buried interface engineering. The perfluorinated copper phthalocyanine (F₁₆CuPc) molecules with strong electronegativity are employed to modify the NiO_x/Me-2PACz substrate, which not only facilitates the crystallization of the perovskite, but also induces the formation of p-type perovskite at its buried interface. We observe a gradual shift of the Fermi level from near valence band at the perovskite buried interface to near conduction band at the perovskite top surface, manifesting the transition from p-type to n-type within the monolithic perovskite layer. Such a p–n homojunction provides an extra electric field for accelerating charge carrier transportation, and thus enhances the device photovoltaic performance. The F₁₆CuPc induced perovskite homojunction solar cells achieved a champion efficiency of 25.0% and it retained over 80% of its initial efficiency for more than 1100 h. We believe that the perovskite homojunction strategy will also pave the way for other perovskite-based optoelectronic devices.

The degradable additive couple is developed to enable pure and preferential-oriented α-FAPbI₃ perovskite with a bandgap of 1.489 eV and robustness against light, heat, and moisture over 1000 h, without the additive residue. The resultant perovskite solar cells achieve a power conversion efficiency of 25.20% with a short current density of 26.40 mA cm⁻² and long-term operational stability of over 1000 h.

Abstract

Pure black-phase FAPbI₃ has always been pursued because of its ideal bandgap (E _g) and high thermal stability. Here, a pair of sacrificial agents containing diethylamine hydrochloride (DEACl) and formamide (Fo) is reported, which can induce the oriented growth of black-phase FAPbI₃ along (111) and will disappear by the aminolysis reaction during perovskite annealing, retaining the E _g of FAPbI₃ as 1.49 eV. In addition, the tensile strain of the target FAPbI₃ is found to be mitigated with a stabilized black phase due to the tilt of FA⁺. The devices based on the pure and stable black-phase (111)-FAPbI₃ achieved a power conversion efficiency of 25.2% and 24.2% (certified 23.51%) with an aperture area of 0.09 and 1.04 cm², respectively. After 1080 h of operation at the maximum power point under 1-sun illumination (100 mW cm⁻²), the devices maintained 91.68 ± 0.72% of the initial efficiencies.