Publication date: 18 September 2024
Source: Joule, Volume 8, Issue 9
Author(s): Luis Victor Torres Merino, Christopher E. Petoukhoff, Oleksandr Matiash, Anand Selvin Subbiah, Carolina Villamil Franco, Pia Dally, Badri Vishal, Sofiia Kosar, Diego Rosas Villalva, Vladyslav Hnapovskyi, Esma Ugur, Sahil Shah, Francisco Peña Camargo, Orestis Karalis, Hannes Hempel, Igal Levine, Rakesh R. Pradhan, Suzana Kralj, Nikhil Kalasariya, Maxime Babics
Herein, Cu(II)Pcs and Ni(II)Pcs peripherally tetra-functionalized with 5-hexylthiophene (HT), 5-hexyl-2,2’-bithiophene (HBT), and tertbutyl groups (TB) are readily synthesized and employed as hole-transporting materials in mixed-ion perovskite ([FAPbI3]0.85[MAPbBr3]0.15) solar cells, achieving power conversion efficiencies up to 20.0%.
Herein, Cu(II)Pcs and Ni(II)Pcs peripherally tetra-functionalized with 5-hexylthiophene (HT), 5-hexyl-2,2′-bithiophene (HBT), and tertbutyl groups (TB) are readily synthesized and employed as hole-transporting materials (HTMs) in mixed-ion perovskite ([FAPbI3]0.85[MAPbBr3]0.15) solar cells, achieving power conversion efficiencies (PCEs) up to 20.0%. Remarkably, both the peripheral functionalization and the central metal are found to play a role in the performance. Through a combination of experimental and theoretical techniques, it is found that the simplest HTM, TB-CuPc, is the best-performing HTM primarily due to its higher hole mobility and a more appropriate highest-occupied molecular orbital, whose enables efficient hole extraction without open-circuit voltage (V oc)losses. This derivative leads to PCEs of 19.96%, which are among the highest values for Pc-based HTMs. Importantly, devices incorporating these HTMs present significantly higher stability compared to those based on spiro-OMeTAD. The results here presented pave the way for more realistic, efficient, and inexpensive photovoltaic devices using phthalocyanine derivatives.
The effect of [2-4 (Methylsulphonyl) Phenyl) Ethylamine Hydrochloride] MSPE-Cl on controlled nucleation and crystallization kinetics within perovskite is studied. The refine film with preferable orientation (100) and passivation of defects are achieved. The larger grains are formed with enhanced charge transportation causing to alleviate nonradiative charge recombination and improve stability with 24.16% power conversion efficiency.
To get maximum efficiency, potential in perovskite solar cells (PSCs) has made it hot research area now a days. Power conversion efficiency of PSCs is increasing by every passing day. Moreover, performance of perovskite absorber layer is important for high efficiency andlong term stability of PSCs. In this work, 2-4 (Methyl sulphonyl) Phenyl) Ethylamine small molecules with functional groups are added inperovskite and enlarged grains are observed in the result. These effects show improvement in the performance of perovskite. Consequently, density of imperfections with additive in PSCs is alleviated and champion efficiency 24.16% has been achieved. Within corporation of additive with polar functional group crystallinity of absorber film is increased, that is confirmed by X-ray diffraction and Uv-Vis results. PL result show absorption is increased with addition ofadditive due to mitigation of nonradiative charge recombination. It is confirmed by GIWAX that charge transportation is increased since output peakintensity for (100) plane is larger than that of input. Overall, efficiencyis increased from 22% for control and exceeding 24% and stability enhanced with incorporation of small molecules.
The authors review the material properties of and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) layers and then presents a theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers. Furthermore, the authors focus on the recent developments in the implementation of nc-SiOx:H nd amorphous silicon oxide films for SHJ, passivating contacts, and perovskite/silicon tandem devices.
Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc-SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc-SiOx:H and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped nc-SiOx:H layers, the effect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc-SiOx:H and hydrogenated amorphous silicon oxide (a-SiOx:H) films for SHJ, passivating contacts, and perovskite/silicon tandem devices.
Unintentional contaminants-related defects, which arise simultaneously with the intrinsic defects during the fabrication process, significantly impact the material properties and the device performance. By regulating the growth conditions, the deepest trap states in Sb2Se3 are completely suppressed. The corresponding carrier lifetime increases from 0.37 ps to 3.4 ps, and the devices achieve a champion PCE of up to 10.41%.
Deep-level defects in semiconductor materials usually induce carrier trapping and non-radiative recombination. However, defects caused by unintentional contaminants in antimony selenide (Sb2Se3) solar cells have rarely been reported. Herein, the correlation between defect properties and unintentional impurities in the Sb2Se3 absorber is investigated, which is prepared by injection vapor deposition with Sb2Se3 source purities ranging from 99.9% to 99.9999%. The analysis of deep-level transient spectra reveals that an increase in impurity concentration does not result in new defect types. Nevertheless, the higher impurity level causes an increase in both the defect density and the capture cross section of the original defect. To address this challenge, defect engineering is developed to regulate the growth of the Sb2Se3 absorber. This strategy completely suppresses deepest defect states E3, a mixture of intrinsic defect (SbSe) and impurity Si related defect. As a result, the carrier lifetime increases significantly from 0.37 to 3.4 ps. This enables to fabricate Sb2Se3 solar cells with a power conversion efficiency of 10.41%. This work uncovers the characteristics of unintentional contaminant-related defects, and provides a strategy for fabricating highly efficient Sb2Se3 solar cells with low-purity source materials.
Dual-band photodiode comprising two vertically solution-processed perovskite heterojunctions is fabricated by a high-throughput blading process. The outstanding charge transport capacity of perovskites enables the operation speed of tens of MHz for both spectral bands, and achieves the feasibility of a novel alternating current (AC) driven imaging mode.
Multispectral imaging that captures multiple band information for effective environmental or object identification is of great interest in medical, vision, military, and space applications. Monolithic stacked detectors based on epitaxial electronics have been the principal option for infrared dual-band imagers. However, the integration of these single-band units would inevitably lead to performance reduction, high fabrication cost, and low reproducibility yield, which limits the widespread application of such technology. Here, a high-throughput blade coating process is demonstrated to fabricate monolithic double-perovskite-layer photodiodes with preferential crystallographic morphology and high reproductivity. The device delivers electrically switchable dual-band response with a dark current below 10−9 mA cm−2, a selective spectral response of 300–1100 nm, and bandwidths of 16.5/>20 MHz for two distinct bands. Furthermore, such device configuration can concurrently capture dual-color spectral information under an AC-driven mode, enabling the complementary dual-spectral imaging for bioimaging and environmental monitoring.
A gel precursor strategy is developed to achieve highly oriented and homogeneous α-formamidinium lead iodide films without anti-solvent extraction. The incorporation of N,N′-dimethylpropyleneurea, and alkylammonium chloride forms extended iodoplumbate clusters with an amorphous structure that ensures uniform solute distribution. This not only enhances film homogeneity but also boosts the efficiency and long-term stability of perovskite solar cells.
Pure-phase α-formamidinium lead iodide (α-FAPbI3) perovskite solar cells (PSCs) possess potential high efficiency because of suitable bandgap. However, achieving high-quality α-FAPbI3 films during the spin-coating process is challenging without anti-solvent extraction, due to the spontaneous formation of the more stable δ-FAPbI3 phase and the complexity of multi-component perovskite precursor solutions. Here a gel precursor with an amorphous structure to eliminate the need for anti-solvent extraction in achieving the homogeneous and highly oriented pure-phase α-FAPbI3 is devised films. The incorporation of N,N′-dimethylpropyleneurea, and alkylammonium chloride results in extended iodoplumbate clusters in the perovskite precursor solution. In situ, spectroscopic analysis reveals that the emergence of the stable amorphous gel precursor during the initial solidification stage ensures a uniform solute distribution. This effectively prevents preferentially oriented growth in the crystal phase precursor, leading to a significant enhancement in film homogeneity. As a result, power conversion efficiencies of 24.17% for the PSC, and 19.3% for the module are achieved, along with superior operational stability, retaining 96.1% of their initial efficiency after 850 h at the maximum power point tracking. These demonstrate the best performance for the reported pure-phase α-FAPbI3 PSCs without anti-solvent extraction, showing great promise for scalable manufacture.
The natural molecule anethole is explored to control perovskite crystallization during two-step sequential deposition. The strong hydrogen bond interactions between anethole and formamidine ion (FA+) inhibit the high reactivity of FA+ and decelerate the crystallization kinetics, facilitating the formation of FA-based perovskite films with high crystallinity. The fabricated planar hole transport layer-free carbon electrode perovskite solar cells deliver an efficiency of 20.41%.
Two-step sequential deposition is a widespread technique for the fabrication of perovskite films, renowned for its better control of the crystallization process. However, achieving a well-controlled and complete reaction of PbI2 by organic ammonium salts remains a key challenge. Previous studies have predominantly focused on regulating the properties of the PbI2 layer while paying less attention to the high reactivity of organic ammonium salts. In this study, the natural molecule anethole is first explored to control perovskite crystallization during two-step sequential deposition, focusing on the reactivity modulation of organic formamidine ion (FA+). It is demonstrated that FA+ exhibits strong hydrogen bond interactions with anethole, inhibiting the high reactivity of FA+ and effectively delaying the rapid reaction between FAI and PbI2. This decelerates the crystallization kinetics of perovskite films, facilitating the orderly and complete reaction of PbI2 by FAI while suppressing detrimental δ-phase formation. Consequently, FA-based perovskite films with high crystallinity, preferred orientation, and low defect state density are obtained. The fabricated planar hole transport layer-free carbon electrode perovskite solar cells deliver an efficiency of 20.41% (certified efficiency of 20.0%), which is a new record for this kind of solar cell.
Asymmetrically elongated non-fullerene acceptors (NFAs) are designed with high solubility in o-xylene and miscibility with a PM6 donor. In particular, L8-BO(HU-DT) leads to the formation of homogeneous and uniform PM6:NFA:PC70BM films via slot-die coating, which in turn are used to fabricate 200 cm2 eco-solvent-processed modules with an APCE of 11.44%. This work highlights the significance of alkyl chain fine-tuning for high-performance organic solar modules.
With the drive toward the development of large-area organic solar cells (OSCs), there is a critical need for advanced fabrication techniques that ensure both their efficiency and scalability. In particular, a shift from toxic halogenated solvents to safer non-halogenated alternatives such as o-xylene, which have lower environmental and health impacts, is required. However, transitioning to non-halogenated solvents can lead to serious problems, including aggregation within the active layer, which compromises film morphology and the resulting efficiency of OSCs. To address this aggregation, in the present study, the 2-ethylhexyl (EH) groups in L8-BO(EH-EH) are replaced with longer chains (2-heptylundecyl [HU], 2-decyltetradecyl [DT], and 2-dodecylhexadecyl [DH] groups) to synthesize the non-fullerene acceptors (NFAs) of L8-BO(HU-HU), L8-BO(HU-DT), and L8-BO(HU-DH). The NFAs with the longer alkyl chains are highly soluble in o-xylene and produce highly uniform films, making them more suitable for use in large-area OSCs. Using the NFAs, slot-die-coated organic solar modules with an active area of 200 cm2 are fabricated; the L8-BO(HU-DT)-based module exhibits an impressive power conversion efficiency of 11.44%. This work thus underscores the asymmetrical elongation of alkyl chains in the NFAs to mitigate severe NFA phase separation and improve film printability in the practical production of organic solar modules.
Introducing a spatially stereo-structured iridium complex, fac-Ir(tBufppy)3, into OSCs extends exciton lifetimes, suppresses recombination, and optimizes active layer morphology, resulting in an improved PCE of 18.54% enabled by green solvent processing. This work demonstrates that developing triplet metal complexes with excellent compatibility with organic host materials is an important strategy for achieving highly efficient green solvent-processed OSCs.
In organic solar cells (OSCs), the short exciton lifetime poses a significant limitation to exciton diffusion and dissociation. Extending exciton lifetime and suppressing recombination are crucial strategies for improving the OSC performance. Herein, an effective approach is proposed by introducing the phosphorescent emitter, tris(2-(4-(tert-butyl)phenyl)-5-fluoropyridine)Iridium(III), with long-lived triplet exciton lifetime in OSCs. This research reveals that the steric structure of fac-Ir(tBufppy)3 exhibits excellent compatibility with both the donor PM6 and acceptor BTP-eC9, maintaining efficiencies of over 90% even with a 30% third component loading. Moreover, a 10% addition of fac-Ir(tBufppy)3 mitigates excessive aggregation in the acceptor BTP-eC9, optimizing the active layer morphology and improving the fill factor. Transient absorption spectroscopy and transient photoluminescence measurements demonstrate that the introduction of fac-Ir(tBufppy)3 significantly extends exciton lifetimes and suppresses recombination, which increases the short-circuit current (J SC). Ultimately, employing the non-halogenated solvent o-xylene for processing, an impressive power conversion efficiency (PCE) of 18.54% is achieved in devices based on PM6:10%fac-Ir(tBufppy)3:BTP-eC9, surpassing the efficiency of binary PM6:BTP-eC9 devices (17.41%). This work provides a promising approach to further improve the PCEs in binary OSCs by introducing a phosphorescent iridium(III) complex as the third component.
This review presents state-of-the-art strategies to improve the efficiency of 2D PSCs, focusing on component engineering, crystal structure and photovoltaic properties. The strategies around solution chemical engineering, processing technique and interface optimization, are systematically discussed. Finally, challenges and perspectives associated with 2D perovskites are outlined to provide insights into potential improvements in photovoltaic performance.
In the quest for durable photovoltaic devices, 2D halide perovskites have emerged as a focus of extensive research. However, the reduced dimension in structure is accompanied by inferior optical-electrical properties, such as widened band gap, enhanced exciton binding energy, and obstructed charge transport. As a result, the efficiency of 2D perovskite solar cells (PSCs) lags significantly behind their 3D counterparts. To overcome these constraints, extensive investigations into materials and processing techniques are pursued rigorously to augment the efficiency of 2D PSCs. Herein, The cutting-edge delve into developments in 2D PSCs, with a focus on chemical and material engineering, as well as their structure and photovoltaic properties. The review starts with an introduction of the crystal structure, followed by the key evaluation criteria of 2D PSCs. Then, the strategies around solution chemical engineering, processing technique, and interface optimization, to simultaneously boost efficiency and stability are systematically discussed. Finally, the challenges and perspectives associated with 2D perovskites to provide insights into potential improvements in photovoltaic performance will be outlined.
Electron transport layer (ETL) materials have been rationally designed for in situ blending to co-deposit ETL and light-absorbing layers simultaneously in conventional perovskite solar cells. Such a strategy significantly improves the qualities of perovskite growth and buried interface to improve charge transport/collection. A record high power conversion efficiency over 24% is achieved for organic ETLs based devices.
Simplifying the manufacturing processes of multilayered high-performance perovskite solar cells (PSCs) is yet of vital importance for their cost-effective production. Herein, an in situ blending strategy is presented for co-deposition of electron transport layer (ETL) and perovskite absorber by incorporating (3-(7-butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo- [lmn][3,8]phenanthrolin-2(1H)-yl)propyl)phosphonic acid (NDP) into the perovskite precursor solutions. The phosphonic acid-like anchoring group coupled with its large molecular size drives the migration of NDP toward indium tin oxide (ITO) surface to form a distinct ETL during perovskite film forming. This strategy circumvents the critical wetting issue and simultaneously improves the interfacial charge collection efficiencies. Consequently, n-i-p PSCs based on in situ blended NDP achieve a champion power conversion efficiency (PCE) of 24.01%, which is one of the highest values for PSCs using organic ETLs. This performance is notably higher than that of ETL-free (21.19%) and independently spin-coated (21.42%) counterparts. More encouragingly, the in situ blending strategy dramatically enhances the device stability under harsh conditions by retaining over 90% of initial efficiencies after 250 h in 100 °C or 65% humidity storage. Moreover, this strategy is universally adaptable to various perovskite compositions, device architectures, and electron transport materials (ETMs), showing great potential for applications in diverse optoelectronic devices.
Oily Allicin is introduced into perovskite solar cells to achieve grain wrapping under different stressors, which promotes defect contact and prevents ionic migration. A power conversion efficiency of 25.07% with an FF (fill factor) of 84.03% is achieved, which reaches 93.16% of the FF S–Q limit.
The buried interface properties of the perovskite solar cells (PSCs) play a crucial role in the power conversion efficiency (PCE) and operational stability. The metal-oxide/perovskite heterogeneous interfaces are highly defective and cause serious ion migration. However, the buried and unexposed bottom interface and simultaneous stabilization of grain boundaries receive less attention and effective solutions. To tackle this problem, a solid–liquid strategy is employed by introducing oily-additive allicin at the buried interface to passivate the shallow (V I and Vo) and deep traps (V Pb and Pb I). Interestingly, oily status allicin fills the pinholes at the heterointerface and wraps the perovskite grains, suppressing the ion migration during the photoaging process. As a result, an outstanding PCE of 25.07% is achieved with a remarkable fill factor (FF) of 84.03%. The modified devices can maintain 94.51% of the original PCE after light soaking under 1-sun illumination for 1000 h. This work demonstrates a buried interface modification method that employs an eco-friendly additive, which helps promote the development of PSCs with high performance and stability.
A polymer-assisted 5FTPP/PCBM supramolecular donor-acceptor (D–A) interface self-assembly strategy can minimize interfacial energy losses by addressing thermalization, conduction band offset, and nonradiative recombination, while inhibiting the adverse effect of FA+ volatilization under thermal stress by multidentate anchoring.
2D perovskite passivation strategies effectively reduce defect-assisted carrier nonradiative recombination losses on the perovskite surface. Nonetheless, severe energy losses are causing by carrier thermalization, interfacial nonradiative recombination, and conduction band offset still persist at heterojunction perovskite/PCBM interfaces, which limits further performance enhancement of inverted heterojunction PSCs. Here, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (5FTPP) is introduced between 3D/2D perovskite heterojunction and PCBM. Compared to tetraphenylporphyrin without electron-withdrawing fluoro-substituents, 5FTPP can self-assemble with PCBM at interface into donor–acceptor (D–A) complex with stronger supramolecular interaction and lower energy transfer losses. This rapid energy transfer from donor (5FTPP) to acceptor (PCBM) within femtosecond scale is demonstrated to enlarge hot carrier extraction rates and ranges, reducing thermalization losses. Furthermore, the incorporation of polystyrene derivative (PD) reinforces D–A interaction by inhibiting self-π–π stacking of 5FTPP, while fine-tuning conduction band offset and suppressing interfacial nonradiative recombination via Schottky barrier, dipole, and n-doping. Notably, the multidentate anchoring of PD-5FTPP with FA+, Pb2+, and I− mitigates the adverse effects of FA+ volatilization during thermal stress. Ultimately, devices with PD-5FTPP achieve a power conversion efficiency of 25.78% (certified: 25.36%), maintaining over 90% of initial efficiency after 1000 h of continuous illumination at the maximum power point (65 °C) under ISOS-L-2 protocol.
Inner/outer side-chain modification of non-fullerene acceptors (NFAs) has a pronounced impact on large-area film formation at room temperature. Herein, a highly efficient sub-module is reported by designing a series of Y6 derivatives with modified branched inner/outer side chains. The optimized NFA blend exhibits the best power conversion efficiency of 12.2% with a 55 cm2 photoactive area.
Achieving efficient and large-area organic solar modules via non-halogenated solution processing is vital for the commercialization yet challenging. The primary hurdle is the conservation of the ideal film-formation kinetics and bulk-heterojunction (BHJ) morphology of large-area organic solar cells (OSCs). A cutting-edge non-fullerene acceptor (NFA), Y6, shows efficient power conversion efficiencies (PCEs) when processed with toxic halogenated solvents, but exhibits poor solubility in non-halogenated solvents, resulting in suboptimal morphology. Therefore, in this study, the impact of modifying the inner and outer side-chains of Y6 on OSC performance is investigated. The study reveals that blending a polymer donor, PM6, with one of the modified NFAs, namely N-HD, achieved an impressive PCE of 18.3% on a small-area OSC. This modified NFA displays improved solubility in o-xylene at room temperature, which facilitated the formation of a favorable BHJ morphology. A large-area (55 cm2) sub-module delivered an impressive PCE of 12.2% based on N-HD using o-xylene under ambient conditions. These findings underscore the significant impact of the modified Y6 derivatives on structural arrangements and film processing over a large-area module at room temperature. Consequently, these results are poised to deepen the comprehension of the scaling challenges encountered in OSCs and may contribute to their commercialization.
Blade-coated mixed Tin–lead perovskites face a daunting challenge: rapid and uncontrollable crystallization, which leads to numerous defects and significant stress. Utilizing multiple carboxyl and amino groups can effectively control crystal growth and boost crystallinity. This enables blade-coated single-junction narrow-bandgap perovskite solar cells and their two-terminal tandems to achieve power conversion efficiencies of 20.95% and 27.20%, respectively.
Mixed tin–lead (Sn–Pb) perovskites often face a daunting challenge: rapid and uncontrollable crystallization, leading to a plethora of defects and significant stress. This issue is particularly exacerbated during the blade-coating preparation of scalable Sn–Pb perovskite films. In this study, a facile strategy involving the addition of ammonium citrate (AC) to narrow-bandgap mixed Sn–Pb perovskite precursors is introduced. AC, armed with its arsenal of multiple carboxyl and amino groups, acts as a virtuoso conductor, orchestrating controlled crystal growth by harmonizing with Pb2+ and Sn2+ ions. This addition significantly boosts the crystallinity of the perovskite films, alleviates interface stress, inhibits Sn2+ oxidation, and mitigates interfacial defects. Consequently, The blade-coated AC-incorporated mixed Sn–Pb perovskite solar cells achieve a high photovoltaic conversion efficiency of nearly 21%. Furthermore, extending this strategy to two-terminal all-perovskite tandem solar cells yielded a remarkable maximum efficiency of 27.20%. This work presents an effective strategy for producing efficient blade-coated mixed Sn–Pb perovskite solar cells, heralding a pathway toward scalable fabrication of all-perovskite tandem solar cells.
The study explores the use of the reductive molecule NH5F2 with a bi-fluoride anion to improve tin perovskite solar cells. This molecule reduces coordination energy with Sn2+, preventing phase segregation and enhancing film growth, resulting in a highly oriented, low-defect perovskite film, leading to a solar cell efficiency of 15.04%, one of the highest reported.
Phase segregation can bring low crystallinity and orientation, giving rise to poor carrier transport and high defect density, leading to poor device performance. In order to reduce oxidation and defect density and regulate film growth, lots of reductive additives such as SnF2 are explored as additives in tin perovskite film growth. Despite the oxidation is effectively reduced, it induces phase segregation. Herein, a reductive molecule NH5F2 with a bi-fluoride anion is explored to address this challenge for tin perovskite solar cells. This bi-fluoride anion reduces coordination energy with Sn2+ compared to SnF2, hence the byproduct of [F─H─F]− can be eliminated during the film annealing process, effectively preventing fluoride segregation. As a result, a highly oriented perovskite film with reduced oxidation is fabricated. The film shows reduced defect density and carrier recombination, leading to improved current density. Consequently, a tin-based perovskite solar cell with an efficiency of 15.04% is fabricated, ranking as one of the highest efficiencies reported up to now.
The salt-based catalyzer strategy enhances the wettability of the Fluorine-doped Tin Oxide substrate and its chemical interaction with perovskite precursor, as well as promotes the perovskite heterogeneous nucleation, giving high-quality perovskite films. Consequently, a simple perovskite solar cell without the electron transport layer shows a remarkable efficiency of 23.04%.
Charge transport layers are critical components in perovskite solar cells (PSCs) for achieving satisfied power conversion efficiencies (PCEs) and device stability. However, these layers often bring incompatible interfaces and complex fabrication, limiting the stability and scalability of PSC technology. Here an alternative strategy of salt-based catalyzer (SBC) is proposed to regulate the heterogeneous nucleation of perovskite, which enables uniform and well-controlled perovskite coverage directly onto the salt-treated substrate without electron transport layers (ETLs). By carefully adjusting the cations, anions, and the thickness of SBC, high-quality perovskite films along with superior buried interfaces suppress the carrier recombination losses and strengthen the interfacial stability, promoting the resultant device to achieve a record PCE of 23.04%, which represents the highest reported efficiency for ETL-free PSCs. Meanwhile, the SBC technique can be well extended to large-area, flexible, and module-based devices. More encouragingly, the SBC-based unencapsulated devices exhibit remarkable operational stability by retaining over 90% of initial efficiency for 1540 h under illumination and for 6312 h in an air environment. This work provides an advisable way to fabricate efficient and stable ETL-free PSCs toward reliable and cost-effective production.
This research delves into molecular interactions of DBrDIB solid additive with the polymer donor or small molecule acceptor, emphasizing optimized BHJ morphology processed from halogen-free solvent. Utilizing o-xylene/DBrDIB, the PM6:Y6-BO and PM6:Y6-HU device achieve impressive PCEs of 17.9% and 19.1%, respectively. These insights will aid in designing high-performance OSCs with eco-friendly processing.
Developing non-halogenated solvent-processed organic solar cells (OSCs) demands precise control over the bulk-heterojunction (BHJ) morphology of the photoactive layer. However, the limited solubility of halogen-free solvents to photoactive materials hinders microstructure morphology fine-tuning for boosting photovoltaic performance. This study not only examines the debated intermolecular interactions between the DBrDIB solid additive and photoactive materials but also analyzes the substantial influence of volatile solid additive on the BHJ morphological properties. The DBrDIB effectively restricts the excessive aggregation of Y6-BO and regulates the phase separation, which is attributed to strong intermolecular interactions with Y6-BO and rapid quenching during morphology formation. It then achieves a well-mixed D/A phase with favorable domain size, resulting in a balanced aggregation and dispersion of D/A, ultimately leading to markedly enhanced charge transfer and transport as well as suppressed charge recombination. The transformative use of the o-xylene/DBrDIB solvent system propels PM6:Y6-BO and PM6:Y6-HU OSCs to impressive efficiencies of 17.9% and 19.1%, respectively, outperforming those of the control devices. These findings provide crucial insights into theoretical and experimental areas, offering actionable guidelines for designing high-performance OSCs processed from halogen-free solvent.
Double-fibril network morphology (DFNM) is constructed and optimized in the all-polymer solar cells (all-PSCs) with the use of 2-alkoxynaphthalene volatile solid additives. Through subtly modifying the alkoxy of 2-alkoxynaphthalene additives, improved molecular packing and well-defined DFMN are simultaneously realized, leading to a record efficiency of 19.50% for all-PSCs.
Double-fibril network morphology (DFNM), in which the donor and the acceptor can self-assemble into a double-fibril structure, is beneficial for exciton dissociation and charge transport in organic solar cells. Herein, it is demonstrated that such DFNM can be constructed and optimized in all-polymer solar cells (all-PSCs) with the assistance of 2-alkoxynaphthalene volatile solid additives. It is revealed that the incorporation of 2-alkoxynaphthalene can induce a stepwise regulation in the aggregation of donor and acceptor molecules during film casting and thermal annealing processes. Through altering the alkoxy of 2-alkoxynaphthalene solid additives, both the intermolecular interactions and molecular miscibility with the host materials can be precisely tuned, which allows for the optimization of the molecular aggregation process and facilitation of molecular self-assembly, and thus leading to reinforced molecular packing and optimized DFNM. As a result, an unprecedented efficiency of 19.50% (certified as 19.1%) is obtained for 2-ethoxynaphthalene-processed PM6:PY-DT-X all-PSCs with excellent photostability (T 80 = 1750 h). This work reveals that the optimization of DFNM via solid additive strategy is a promising avenue to boosting the performance of all-PSCs.
Manipulating the alkyl inner side chain of the small molecule acceptors assists in regulating molecular bandgap, energy levels, and intermolecular interaction, which is conducive to optimizing the trade-off among short-circuit current density, open-circuit voltage, and fill factor. Consequently, the optimal as-cast organic solar cells (OSCs) deliver top-ranked efficiencies of over 18%.
As-cast organic solar cells (OSCs) possess tremendous potential for low-cost commercial applications. Herein, five small-molecule acceptors (A1–A5) are designed and synthesized by selectively and elaborately extending the alkyl inner side chain flanking on the pyrrole motif to prepare efficient as-cast devices. As the extension of the alkyl chain, the absorption spectra of the films are gradually blue-shifted from A1 to A5 along with slightly uplifted lowest unoccupied molecular orbital energy levels, which is conducive for optimizing the trade-off between short-circuit current density and open-circuit voltage of the devices. Moreover, a longer alkyl chain improves compatibility between the acceptor and donor. The in situ technique clarifies that good compatibility will prolong molecular assembly time and assist in the preferential formation of the donor phase, where the acceptor precipitates in the framework formed by the donor. The corresponding film-formation dynamics facilitate the realization of favorable film morphology with a suitable fibrillar structure, molecular stacking, and vertical phase separation, resulting in an incremental fill factor from A1 to A5-based devices. Consequently, the A3-based as-cast OSCs achieve a top-ranked efficiency of 18.29%. This work proposes an ingenious strategy to manipulate intermolecular interactions and control the film-formation process for constructing high-performance as-cast devices.
Nature Photonics, Published online: 17 July 2024; doi:10.1038/s41566-024-01476-1
Transient visible-pump terahertz-probe near-field microscopy enables the simultaneous retrieval of the local chemical composition, crystallographic structure, topography and out-of-plane charge-carrier diffusion in perovskite films.Publication date: 16 October 2024
Source: Joule, Volume 8, Issue 10
Author(s): Zhiliang Liu, Zhijun Xiong, Shaofei Yang, Ke Fan, Long Jiang, Yuliang Mao, Chaochao Qin, Sibo Li, Longbin Qiu, Jie Zhang, Francis R. Lin, Linfeng Fei, Yong Hua, Jia Yao, Cao Yu, Jian Zhou, Yimu Chen, Hong Zhang, Haitao Huang, Alex K.-Y. Jen
Highly unstable contact angle of Pb–Sn narrow bandgap (NBG) perovskite ink on PEDOT:PSS induces detrimental voids at the buried interface due to uncontrolled and inhomogeneous nucleation. Prolonging the solution–substrate interaction during blade coating is key to stabilize the wetting. This results in uniform and high-quality NBG perovskite, enabling high-performance NBG perovskite solar modules.
The development of scalable 1.25 eV mixed Pb–Sn perovskite solar modules by blade coating lags behind Pb-based perovskites due to limited understanding of solution–substrate interaction of the perovskite ink on PEDOT:PSS and subsequent gas quenching. To address this challenge, the wet film deposition and quenching process to better understand narrow bandgap perovskite film formation on PEDOT:PSS are studied. It is found that the wetting of Pb–Sn perovskite ink on PEDOT:PSS is highly unstable over relevant coating time scales, causing the contact angles to decrease rapidly from 42° to 16° within seconds. This instability leads to localized irregularities in the wet film, resulting in uneven solvent extraction and inhomogeneous nuclei density. As a result, rough perovskite films with voids at the buried interface are obtained. To overcome this problem, a quasistatic wetting process by reducing the blade coating speed is developed, thereby stabilizing the wetting behavior of Pb–Sn perovskite precursor ink on PEDOT:PSS. This optimized process facilitates the deposition of high-quality, void-free Pb–Sn perovskite films with uniform thickness over 8 cm of coating length using moderate (1.4 bar) N2 quenching. 20% efficient narrow bandgap perovskite solar cells and minimodules with 15.8% active area efficiency on 15.9 cm2 are achieved.
The trade-off between V oc and J sc of pentacyclic SMAs is realized by asymmetry strategy of sulfur-containing branched side chains, and 15.08% PCE is obtained. Active layer morphologies are further optimized by solvent vapor annealing, and device efficiency is increased to 16.18%.
Solution-processible organic solar cells (OSCs) have gained much attention as one of the most promising options for sustainable energy. With rapidly increasing efficiency of OSCs, developing small molecular acceptors (SMAs) with simple molecular structures are critical for reducing the cost of photovoltaics. Herein, three new SMAs (BZ4F-C2SEH, BZ4F-2C2SEH, BZ4F-SEH) are designed by the incorporation of ethyl(2-ethylhexyl)sulfane or (2-ethylhexyl)-sulfane at the β-position of thiophene. As a result, the BZ4F-C2SEH-based devices obtained an optimal PCE of 15.08% with a good balance between open-circuit voltage (V oc = 0.87 V) and short-circuit current density (J sc = 23.27 mA cm−2) by blending with low-cost polymer donor PTQ10. Besides, the BZ4F-C2SEH based devices treated by thermal annealing (TA) and solvent annealing (SVA) deliver a satisfactory power conversion efficiency (PCE) of 16.18% with a V oc of 0.88 V, and a J sc of 23.98 mA cm−2. This work highlights that attaching asymmetric alkylthio side chain at the β-position of thiophene can be used as an effective molecular design strategy to trade off V oc and J sc, thus improving the photovoltaic performance of OSCs.
This work demonstrates a novel method for modifying the ETL, facilitating the low-temperature processing of efficient ITO-free flexible PSCs. Incorporating NDI-B into SnO2 leads to the passivation of defect centers and enhances the charge transport characteristics within the devices; thus, the planar ITO-free n–i–p-structured flexible PSC exhibits a high PCE of 17.48%.
A low-cost and indium-tin-oxide (ITO)-free electrode-based flexible perovskite solar cell (PSC) that can be fabricated by roll-to-roll processing shall be developed for successful commercialization. High processing temperatures present a challenge for the PSC fabrication on flexible substrates. The most efficient planar n–i–p PSC structures, which utilize a metal oxide as an electron transport layer (ETL), necessitate high annealing temperatures. In addition, the device performance deteriorates owing to the migration of halogen ions, which causes the oxidation of the metal electrodes. These drawbacks conflict with the development of highly efficient flexible PSCs fabricated on ITO-free transparent electrodes. Herein, an efficient ETL material that enables low-temperature processing is presented. Tin dioxide (SnO2) is modified by (sulfobetaine-N,N-dimethylamino)propyl naphthalene diimide (NDI-B) and used as an ETL. The NDI-B effectively reduces the interfacial nonradiative recombination between the ETL and perovskite and suppresses the ion migration by passivating oxygen-vacancy defects in SnO2 and strongly interacting with halogen ions, respectively. Based on the NDI-B-blended SnO2 ETL, a record PCE of 17.48% is achieved in the ITO-free flexible PSC fabricated at low temperature.
A series of dimer acceptors linked by flexible conjugation-broken linkers (FCBLs) with different alkyl chains named TX are synthesized and applied to fabricate organic solar cells (OSCs). Interestingly, the FCBLs in dimer acceptors can effectively enhance the mechanical properties and stability of OSCs.
Dimer acceptors in organic solar cells (OSCs) offer distinct advantages, including a well-defined molecular structure and excellent batch-to-batch reproducibility. Their high glass transition temperature (T g) aids in achieving an optimal kinetic morphology, thereby enhancing device stability. Currently, most of dimer acceptor materials are linked with conjugated units in order to obtain high power conversion efficiencies (PCEs). In this study, different from previous works on conjugation-linked dimer acceptors, a novel series of dimer acceptors are synthesized (named T1, T4, T6, and T12), each linked with different flexible alkyl linkers, and investigated their PCEs, device stability, and flexibility robustness. When blended with PM6, the T6-based device achieves a PCE of 17.09%, comparable to the fully conjugated T0-based device's PCE of 17.12%. The molecular dynamics simulations and density functional theory calculations suggested that flexible conjugation-broken linkers (FCBLs) promote intermolecular electronic couplings, thereby maintaining good electron mobilities of dimer acceptors. Notably, the T6-based device exhibits impressive long-term stability with a T80 lifetime of 1427 h, while in the T0-based device, T80 is only 350 h. The present work has thus established the relationship between the length of flexible alkyl linkers in such dimer acceptors and the performance and stability of OSCs, which is important to further designing new materials for the fabrication of efficient and stable OSCs.
