Publication date: 15 June 2024
Source: Nano Energy, Volume 125
Author(s): Jin-Woo Lee, Cheng Sun, Seungbok Lee, Dong Jun Kim, Eun Sung Oh, Tan Ngoc-Lan Phan, Trieu Hoang-Quan Nguyen, Soodeok Seo, Zhengping Tan, Michael J. Lee, Jung-Yong Lee, Xichang Bao, Taek-Soo Kim, Changyeon Lee, Yun-Hi Kim, Bumjoon J. Kim
Publication date: 15 June 2024
Source: Nano Energy, Volume 125
Author(s): Fei Wang, Dawei Duan, Yonggui Sun, Taomiao Wang, Guo Yang, Qiannan Li, Yongjun Li, Xiao Liang, Xianfang Zhou, Xiaokang Sun, Jing Ma, Jin Xiang, Jiajie Zhu, Quanyao Zhu, Kang Zhou, Haoran Lin, Yumeng Shi, Gang Li, Hanlin Hu
Publication date: 15 June 2024
Source: Nano Energy, Volume 125
Author(s): Ran Yin, Rongfei Wu, Wenjing Miao, Kexiang Wang, Weiwei Sun, Xiaonan Huo, Yansheng Sun, Tingting You, Weichang Hao, Penggang Yin
The introduction of 2-Methyltetrahydrofolate (2-MTHF) in a stoichiometric precursor solution is capable of inducing precursor film to generate perovskite films through a simple one-step spin-coating process, more than 15% of toxic solvents can be reduced. The maximum PCE of the solar cell when the 2-MTHF volume fraction is optimized at 15% is improved to 23.58%.
To replace or reduce toxic solvents in perovskite solar cell (PSC) manufacturing, 2-Methyltetrahydrofolate (2-MTHF), as an important raw material for organic synthesis and an excellent solvent, is incorporated in PSCs as an additive cosoluble precursor to fabricate photolayer (FAPbI3) for the first time. It is investigated that this is not only a toxicity-reducing strategy, but also an effective defect passivation method for manufacturing PSCs. The introduction of 2-MTHF in a stoichiometric precursor solution is capable of inducing precursor film to generate perovskite films through a simple one-step spin-coating process, more than 15% of toxic solvents can be reduced. The perovskite trap state is decreased by the passivated perovskite crystal surface thus improving carrier lifetime, extraction rate, and photovoltaic performance. The maximum PCE of the solar cell when the 2-MTHF volume fraction is optimized at 15% is improved to 23.58%, up from 7% in the control. Meanwhile, the notorious J–V hysteresis is much suppressed. Hence, it is expected that novel 2-MTHF will find applications in PSCs and optoelectronic devices.
The solvent polarity and film drying kinetics have a synergistic effect on thin film microstructure and exciton/charge carrier dynamics. After establishing the relationship between polarity–processing–function, the aggregation behavior of small molecule nonfullerene acceptors in solution is further regulated by introducing electrostatic interactions, which demands fine-tuning of the polarity and drying kinetics for enhancing device performance.
In recent years, the emergence of high-efficiency nonfullerene acceptors (NFAs) has pushed the power conversion efficiency (PCE) beyond 19% in organic solar cells (OSCs). For solution processing of the photoactive layers, the study of solvent properties on device performance has become a hot research topic toward up-scaling. Herein, the key roles of balancing solvent polarity and drying kinetics for processing of small molecular NFAs toward high-performance OSCs are revealed. It is demonstrated that the synergistic effect of solvent polarity and drying kinetics significantly affects the multilength scale morphology of solid films and photovoltaic performance. Furthermore, the self-assembly of NFAs in solution and the resulting thin film microstructures induced by electrostatic interactions with polarized additives are even more sensitive to solvent polarity and drying kinetics. Finally, the optimized devices achieve an outstanding PCE of 18.54% by fine-tuning the microstructure with polar solvent and fast-drying kinetics to form improved molecular packing and structure size. The work provides a novel view and deeper insights into the general selection rules of solvents toward the solution processing of high-performance nonfullerene OSCs.
The iron–porphyrin additive can not only promote the oxidation of Spiro-OMeTAD and improve the extraction and transport of holes of HTL, but also passivate the Pb2+ defects of perovskite film and prevent the Li+ from being invaded by water vapor, which enhance the power conversion efficiency and stability of perovskite solar cells significantly.
Spiro-OMeTAD, as a crucial component of hole-transporting layer (HTL), exhibits limited mobility and conductivity, and the lithium bis-trifluoromethanesulfonimide dopant is sensitive to water vapor, which imposes restrictions on the photovoltaic properties of perovskite solar cells (PSCs). Herein, the iron–porphyrin (FePP) is introduced into Spiro-OMeTAD solution as additive, which facilitates the oxidation process of Spiro-OMeTAD, leading to the enhancement of hole mobility and hole extraction and transport. Besides, the surface Pb2+ defects of perovskite film are cured by the presence of carboxylic acids (COOH) in FePP. As a result, the photovoltaic properties of PSCs with FePP additive have been improved with a power conversion efficiency (PCE) of 21.58%. Moreover, FePP can further anchor Li+ ions in HTL to prevent it from being invaded by water vapor. Dramatically, the degradation of unencapsulated devices with FePP is suppressed significantly, which retains 82.0% of its original PCE under 10–20% relative humidity (RH) after 7100 h and maintains about 79.6% of its original PCE under 50–60% RH after 1000 h. Thus, this study shows that the design and development of multifunctional HTL additives holds great potential for achieving highly efficient and durable PSCs.
Two novel PDI-based small molecules with the tailored A-DA'D-A backbone planarity are designed and synthesized, namely ufBTz-2PDI and fBTz-2PDI, as the third component for constructing efficient t-OSCs. The resultant t-OSCs achieved an impressive PCE of 18.56% when incorporating the semi-crystalline fBTz-2PDI into the classical D18:L8-BO system, surpassing the 17.88% and 14.37% attained in b-OSC and t-OSC (D18:L8-BO:ufBTz-2PDI).
Incorporating a third component into binary organic solar cells (b-OSCs) has provided a potential platform to boost power conversion efficiency (PCEs). However, gaining control over the non-equilibrium blend morphology via the molecular design of the perylene diimide (PDI)-based third component toward efficient ternary organic solar cells (t-OSCs) still remains challenging. Herein, two novel PDI derivatives are developed with tailored molecular planarity, namely ufBTz-2PDI and fBTz-2PDI, as the third component for t-OSCs. Notably, after performing a cyclization reaction, the twisted ufBTz-2PDI with an amorphous character transferred to the highly planar fBTz-2PDI followed by a semi-crystalline character. When incorporating the semi-crystalline fBTz-2PDI into the D18:L8-BO system, the resultant t-OSC achieved an impressive PCE of 18.56%, surpassing the 17.88% attained in b-OSCs. In comparison, the addition of amorphous ufBTz-2PDI into the binary system facilitates additional charge trap sites and results in a deteriorative PCE of 14.37%. Additionally, The third component fBTz-2PDI possesses a good generality in optimizing the PCEs of several b-OSCs systems are demonstrated. The results not only provided a novel A-DA'D-A motif for further designing efficient third component but also demonstrated the crucial role of modulated crystallinity of the PDI-based third component in optimizing PCEs of t-OSCs.
Zirconium oxide doped organosilica nanodots as light- and charge-management cathode interlayer for highly efficient and stable inverted organic solar cells are demonstrated for inverted organic solar cells (i-OSCs) with power conversion efficiency over 18% and excellent light-harvesting, charge passivation ability, photostability.
In this work, it is reported that zirconium oxide (ZrO2) doped organosilica nanodots (OSiNDs: ZrO2) with light- and charge-management properties serve as efficient cathode interlayers for high-efficiency inverted organic solar cells (i-OSCs). ZrO2 doping effectively improves the light harvesting of the active layer, the physical contact between the active layer, as well as the electron collection property by habiting charge recombination loss. Consequently, all devices utilizing the OSiNDs: ZrO2 cathode interlayer exhibit enhanced power conversion efficiency (PCE). Specifically, i-OSCs based on PM6:Y6 and PM6:BTP-eC9 achieve remarkable PCEs of 17.16% and 18.43%, respectively. Furthermore, the PCE of device based on PM6:Y6 maintains over 97.2% of its original value following AM 1.5G illumination (including UV light) at 100 mW cm−2 for 600 min.
Volatile benzene additives are developed by the crossbreeding effect of chalcogenation and iodination, which finely tune the molecular crystallinity and optimize the blend morphology, realizing a champion PCE of 19.68% in the ternary blend OSCs with SIB additive.
Volatile solid additives have attracted increasing attention in optimizing the morphology and improving the performance of currently dominated non-fullerene acceptor-based organic solar cells (OSCs). However, the underlying principles governing the rational design of volatile solid additives remain elusive. Herein, a series of efficient volatile solid additives are successfully developed by the crossbreeding effect of chalcogenation and iodination for optimizing the morphology and improving the photovoltaic performances of OSCs. Five benzene derivatives of 1,4-dimethoxybenzene (DOB), 1-iodo-4-methoxybenzene (OIB), 1-iodo-4-methylthiobenzene (SIB), 1,4-dimethylthiobenzene (DSB) and 1,4-diiodobenzene (DIB) are systematically studied, where the widely used DIB is used as the reference. The effect of chalcogenation and iodination on the overall property is comprehensively investigated, which indicates that the versatile functional groups provided various types of noncovalent interactions with the host materials for modulating the morphology. Among them, SIB with the combination of sulphuration and iodination enabled more appropriate interactions with the host blend, giving rise to a highly ordered molecular packing and more favorable morphology. As a result, the binary OSCs based on PM6:L8-BO and PBTz-F:L8-BO as well as the ternary OSCs based on PBTz-F:PM6:L8-BO achieved impressive high PCEs of 18.87%, 18.81% and 19.68%, respectively, which are among the highest values for OSCs.
A high-accuracy machine learning model is established to efficiently screen effective passivation small molecules, where random-extracted and recoverable cross-validation is introduced to enhance the model evaluation accuracy. This facilitated the identification of dominant molecular traits influencing passivation effects and the screening of excellent passivation materials. The consistency between predictions and experimental results confirmed the reliability of the machine learning model.
Utilization of small molecules as passivation materials for perovskite solar cells (PSCs) has gained significant attention recently, with hundreds of small molecules demonstrating passivation effects. In this study, a high-accuracy machine learning model is established to identify the dominant molecular traits influencing passivation and efficiently screen excellent passivation materials among small molecules. To address the challenge of limited available dataset, a novel evaluation method called random-extracted and recoverable cross-validation (RE-RCV) is proposed, which ensures more precise model evaluation with reduced error. Among 31 examined features, dipole moment is identified, hydrogen bond acceptor count, and HOMO-LUMO gap as significant traits affecting passivation, offering valuable guidance for the selection of passivation molecules. The predictions are experimentally validate with three representative molecules: 4-aminobenzenesulfonamide, 4-Chloro-2-hydroxy-5-sulfamoylbenzoic acid, and Phenolsulfonphthalein, which exhibit capability to increase absolute efficiency values by over 2%, with a champion efficiency of 25.41%. This highlights its potential to expedite advancements in PSCs.
This study demonstrates fully blade-coated formamidinium lead iodide (FAPbI3) solar cells with a 22.7% champion power conversion efficiency. The photovoltage of the device is improved by slowing trap emptying in FAPbI3 with Cd doping.
Formamidinium lead iodide (FAPbI3) in its α-phase is among the most desirable perovskite compositions for solar cells. However, because of its transition into the yellow δ-phase at room temperature, it is a challenge to process it in ambient air by scalable fabrication methods. Here the introduction of a trace amount of cadmium (in the form of CdI2) to FAPbI3 is reported and found that it enhances the stability of the perovskite's black α-phase polymorph, inhibits non-radiative recombination events, leads to pin-hole free compact surface morphology, and improves band energy alignment. The 0.6% Cd-doped FAPbI3 solar cells show a champion efficiency of 22.7% for 0.049 cm2 and 16.4% for cm2-scale pixels, which, to the best of the knowledge, are among the highest for air-ambient fully blade-coated pure FAPbI3 solar cells with an n-i-p architecture. Transient absorption microscopy measurements reveal that Cd doping reduces the number of trapped charges and increases their lifetimes, promoting charge accumulation and a higher photovoltage. The study sheds light on the potential of cadmium as a homovalent dopant for the stabilization and performance enhancement of FAPbI3 performance solar cells.
Routine bandgap perovskite (≈1.55 eV) and PbS quantum dot (≈0.95 eV) four-terminal tandem photovoltaics are reported. Quantum dot solar cells achieve a record efficiency of 14.14% based on transparent electrode and band alignment engineering. The four-terminal tandem solar cells achieve an efficiency of 26.12%. The authors provide a new avenue for perovskite-based tandem photovoltaics.
Perovskite-based tandem solar cells have demonstrated high potential for overcoming the Shockley–Queisser limit. Routine bandgap (RBG, ≈1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite-based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four-terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near-infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum-doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, ≈0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi-transparent perovskite solar cells, the four-terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics.
A novel concept is proposed to achieve both precise removal of surface impurities and effective passivation of sub-surface defects in a single step, utilizing a functional polymer-based cleaning strategy. This synergistic effect has significantly boosted power conversion efficiency up to 25.51% by drastically reducing non-radiative recombination and improved operational stability by eliminating ion migration pathways.
Perovskite solar cells (PSCs) suffer from the presence of non-active and metastable species on the surface of solution-processed perovskite films, and their adverse effects on charge extraction and long-term stability cannot be fully addressed by conventional surface passivation strategies. In this study, a novel concept is proposed to achieve both precise removal of surface impurities and effective passivation of sub-surface defects in a single step, utilizing a functional polymer-based cleaning strategy. The moderate intermolecular force provided by the functional polymer and their inherent robust interchain interactions enable effective surface cleaning without disturbing the active crystal lattice. Following surface cleaning, the electron-donating groups (C═O) in the polymer passivate the uncoordinated Pb2+ defects at the sub-surface level. This synergistic effect of surface cleaning and sub-surface defect passivation leads to a drastic reduction in interfacial non-radiative recombination, elimination of ion migration pathways, and prevention of triggers for photodegradation. As a result, the power conversion efficiency (PCE) significantly improved from 22.84% to 25.51%, accompanied by a remarkable enhancement in operational stability. Moreover, the operability and effectiveness of this approach make it highly suitable for scaling up perovskite solar modules in the future.
Fabricating PSCs in ambient air can accelerate their low-cost commercialization. This work performs a compatible optimization on electron transport layer, which enhances the electron extraction and collection. The resulting PSCs achieve an impressive PCE of 25.74% (certificated 25.43%), which is the highest among the air-fabricated PSCs reported to date.
Metal-halide perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology. Fabricating PSCs in ambient air can accelerate their low-cost commercialization, since it can remove the reliance on atmosphere-controlled equipment. However, the power conversion efficiency (PCE) of air-fabricated PSCs still lags behind those fabricated in glovebox. Here, based on a technology to fabricate high-quality perovskite film in ambient air, a compatible optimization is performed on electron transport layer (ETL) to further enhance the photovoltaic performance of PSCs. A soft-templated deposition strategy is proposed that utilizes tetrasodium glutamate diacetate (GLDA) to finely regulate the chemical bath deposition process, leading to an ideal SnO2 ETL with no additive residual. Adopting this feature of no residual, a molecular bridge using β-guanidinopropionic acid (βA) is constructed at the buried interface (SnO2/perovskite), which effectively enhances the electron extraction and decreases electron losses. The resulting PSCs (0.08 cm2) achieve an impressive PCE of 25.74% (certificated 25.43%), which is the highest among the air-fabricated PSCs reported to date. A PCE of 24.61% in 1 cm2-PSCs is also obtained, exhibiting the scalable potential of the technology. In addition, the excellent operational stability of these PSCs is also demonstrated.
Nature Energy, Published online: 28 March 2024; doi:10.1038/s41560-024-01487-w
Understating degradation pathways is critical to the development of perovskite photovoltaics. Thiesbrummel et al. show that internal electric field screening induced by ion migration is a dominant contributor to the operational performance loss of perovskite solar cells.
An effective additive (BAH2) is in situ synthesized in perovskite precursor solution by a two-step addition reaction of but-3-yn-1-amine hydrochloride (BAH) toward formamidinium iodide (FAI) to regulate nucleation and growth of perovskite film along preferred orientation and release lattice strain by forming a low-dimensional perovskite. Consequently, the BAH-treated FACsPbI3 device achieves a remarkable efficiency of 25.19% and improved stability.
Developing an additive to effectively regulate the perovskite crystallization kinetics for the optimized optoelectronic properties of perovskite film plays a vital role in obtaining high efficiency and stable perovskite solar cells (PSCs). Herein, a new additive is designed and directly synthesized in perovskite precursor solution by utilizing an addition reaction between but-3-yn-1-amine hydrochloride (BAH) and formamidinium iodide. It is found that its product may control the intermediate precursor phase for regulating perovskite nucleation, leading to advantageous 2D perovskite to induce growth of perovskite along the preferred [001] orientation with not only released lattice strain but also strong interaction with perovskite to passivate its surface defects. By taking advantage of the above synergistic effects, the optimized PSC delivers an efficiency of 25.19% and a high open-circuit voltage (V OC) of 1.22 V. Additionally, the devices demonstrate good stability, remaining over 90% of their initial efficiencies under ambient atmosphere conditions for 60 days, high temperature of 85 °C for 200 h, or maximum power point tracking for 500 h.
Through the synergistic effect of dimethylammonium and trifluoroacetate, the perovskite solar cells and modules with DMATFA deliver a promising power conversion efficiency of 25.03% (certified 24.65%, 0.1 cm2) and 20.58% (63.74 cm2), respectively. The modified device demonstrates excellent operational stability by maintaining 91% of its initial efficiency after 1520 h of maximum power point continuous tracking.
Ion migration-induced intrinsic instability and large-area fabrication pose a tough challenge for the commercial deployment of perovskite photovoltaics. Herein, an interface heterojunction and metal electrode stabilization strategy is developed by suppressing ion migration via managing lead-based imperfections. After screening a series of cations and nonhalide anions, the ideal organic salt molecule dimethylammonium trifluoroacetate (DMATFA) consisting of dimethylammonium (DMA+) cation and trifluoroacetate (TFA−) anion is selected to manipulate the surface of perovskite films. DMA+ enables the conversion of active excess and/or unreacted PbI2 into stable new phase DMAPbI3, inhibiting photodecomposition of PbI2 and ion migration. Meanwhile, TFA− can suppress iodide ion migration through passivating undercoordinated Pb2+ and/or iodide vacancies. DMA+ and TFA− synergistically stabilize the heterojunction interface and silver electrode. The DMATFA-treated inverted perovskite solar cells and modules achieve a maximum efficiency of 25.03% (certified 24.65%, 0.1 cm2) and 20.58% (63.74 cm2), respectively, which is the record efficiency ever reported for the devices based on vacuum flash evaporation technology. The DMATFA modification results in outstanding operational stability, as evidenced by maintaining 91% of its original efficiency after 1520 h of maximum power point continuous tracking.
This work demonstrates that effective suppression of vacancy defects can be achieved by a rapid collective transformation of lead polyhalides through the Kornblum oxidation reaction of α-iodo ketone that releases halide ions. As a result, the best thermal stability of formamidinium–cesium mixed-cation compositions (FACs)-based perovskite solar cells is achieved.
The iodide vacancy defects generated during the perovskite crystallization process are a common issue that limits the efficiency and stability of perovskite solar cells (PSCs). Although excessive ionic iodides have been used to compensate for these vacancies, they are not effective in reducing defects through modulating the perovskite crystallization. Moreover, these iodide ions present in the perovskite films can act as interstitial defects, which are detrimental to the stability of the perovskite. Here, an effective approach to suppress the formation of vacancy defects by manipulating the coordination chemistry of lead polyhalides during perovskite crystallization is demonstrated. To achieve this suppression, an α-iodo ketone is introduced to undergo a process of Kornblum oxidation reaction that releases halide ions. This process induces a rapid collective transformation of lead polyhalides during the nucleation process and significantly reduces iodide vacancy defects. As a result, the ion mobility is decreased by one order of magnitude in perovskite film and the PSC achieves significantly improved thermal stability, maintaining 82% of its initial power conversion efficiency at 85 °C for 2800 h. These findings highlight the potential of halide ions released by the Kornblum oxidation reaction, which can be widely used for achieving high-performance perovskite optoelectronics.
Interlayer-spacer conformation induces multiple hydrogen bonds in new 2D DJ perovskite toward highly efficient optoelectronic devices with exceptional sensitivity to UV and X-ray photons, while also demonstrating excellent applicability for UV weak-light imaging.
Two-dimensional (2D) Dion–Jacobson (DJ) perovskites typically outperform Ruddlesden–Popper (RP) analogs in terms of photodetection (PD). However, the mechanism behind this enhanced performance remains elusive. Theoretical calculations for elucidating interlayer spacer conformation-induced multiple hydrogen bonds in 2D perovskite are presented, along with the synthesis of DPAPbBr4 (DPB) single crystals (SCs) and their PD properties under X-ray/ultraviolet (UV) excitation. The high-quality DPB SC enhances PD with exceptional photoresponse attributes, including a high on/off ratio (4.89 × 104), high responsivity (2.44 A W⁻1), along with large dynamic linear range (154 dB) and low detection limit (7.1 nW cm⁻2), which are currently the best results among 2D perovskite SC detectors, respectively. Importantly, high-resolution images are obtained under UV illumination with weak light levels. The SC X-ray detector exhibits a high sensitivity of 663 µC Gyair⁻1 cm–2 at 10 V and a detection limit of 1.44 µGyair s⁻1. This study explores 2D DJ perovskites for efficient and innovative optoelectronic applications.
Z19, designed by synergistic side-chain engineering, affords binary organic solar cells (OSCs) with an impressive PCE of 19.2% at a high open-circuit voltage (V OC), 1.002 V. This is the best performance ever reported for OSCs, V OC > 1.0 V. Indications are that such design of organic semiconductors, considering the energy-gap law, may offer the next efficiency breakthrough in OSCs.
Restricted by the energy-gap law, state-of-the-art organic solar cells (OSCs) exhibit relatively low open-circuit voltage (V OC) because of large nonradiative energy losses (ΔE nonrad). Moreover, the trade-off between V OC and external quantum efficiency (EQE) of OSCs is more distinctive; the power conversion efficiencies (PCEs) of OSCs are still <15% with V OCs of >1.0 V. Herein, the electronic properties and aggregation behaviors of non-fullerene acceptors (NFAs) are carefully considered and then a new NFA (Z19) is delicately designed by simultaneously introducing alkoxy and phenyl-substituted alkyl chains to the conjugated backbone. Z19 exhibits a hypochromatic-shifted absorption spectrum, high-lying lowest unoccupied molecular orbital energy level and ordered 2D packing mode. The D18:Z19-based blend film exhibits favorable phase separation with face-on dominated molecular orientation, facilitating charge transport properties. Consequently, D18:Z19 binary devices afford an exciting PCE of 19.2% with a high V OC of 1.002 V, surpassing Y6-2O-based devices. The former is the highest PCE reported to date for OSCs with V OCs of >1.0 V. Moreover, the ΔE nonrad of Z19- (0.200 eV) and Y6-2O-based (0.155 eV) devices are lower than that of Y6-based (0.239 eV) devices. Indications are that the design of such NFA, considering the energy-gap law, could promote a new breakthrough in OSCs.
A new insulating and hydrophobic fluorinated polyimide was employed as the interface layer between perovskite and hole transport layer in perovskite solar cells. This insulating interface layer facilitates carrier transport via the tunneling effect while effectively passivating defects and providing field-effect passivation. The optimized devices attained a remarkable power conversion efficiency of 24.61 % and demonstrated excellent stability.
Despite the remarkable progress of perovskite solar cells (PSCs), challenges remain in terms of finding effective and viable strategies to enhance their long-term stability while maintaining high efficiency. In this study, a new insulating and hydrophobic fluorinated polyimide (FPI: 6FDA-6FAPB) was used as the interface layer between the perovskite layer and the hole transport layer (HTL) in PSCs. The functional groups of FPI play a pivotal role in passivating interface defects within the device. Due to its high work function, FPI demonstrates field-effect passivation (FEP) capabilities as an interface layer, effectively mitigating non-radiative recombination at the interface. Notably, the FPI insulating interface layer does not impede carrier transmission at the interface, which is attributed to the presence of hole tunneling effects. The optimized PSCs achieve an outstanding power conversion efficiency (PCE) of 24.61 % and demonstrate excellent stability, showcasing the efficacy of FPI in enhancing device performance and reliability.
Non-halogenated solvent-processed organic solar cells with approaching 20% efficiency and improved photostability were fabricated by incorporating a new trimeric guest acceptor named Tri-V into PM6:L8-BO-X binary blend, wherein Tri-V can effectively restrict the excessive aggregation of L8-BO-X, thus leading to favorable phase-separation morphology and desirable molecular packing.
The development of high-efficiency organic solar cells (OSCs) processed from non-halogenated solvents is crucially important for their scale-up industry production. However, owing to the difficulty of regulating molecular aggregation, there is a huge efficiency gap between non-halogenated and halogenated solvent processed OSCs. Herein, we fabricate o-xylene processed OSCs with approaching 20 % efficiency by incorporating a trimeric guest acceptor named Tri-V into the PM6:L8-BO-X host blend. The incorporation of Tri-V effectively restricts the excessive aggregation of L8-BO-X, regulates the molecular packing and optimizes the phase-separation morphology, which leads to mitigated trap density states, reduced energy loss and suppressed charge recombination. Consequently, the PM6:L8-BO-X:Tri-V-based device achieves an efficiency of 19.82 %, representing the highest efficiency for non-halogenated solvent-processed OSCs reported to date. Noticeably, with the addition of Tri-V, the ternary device shows an improved photostability than binary PM6:L8-BO-X-based device, and maintains 80 % of the initial efficiency after continuous illumination for 1380 h. This work provides a feasible approach for fabricating high-efficiency, stable, eco-friendly OSCs, and sheds new light on the large-scale industrial production of OSCs.
By controlling connecting sites and halogen substitutions, four dimerized acceptors were designed and synthesized. Thanks to the modification of molecular structure, a champion efficiency of 18.07 % was achieved in FDY-m-TAT-based rigid devices. Importantly, FDY-m-TAT-based intrinsically stretchable devices achieved high performance (power conversion efficiency=14.29 %) and excellent stretchability (crack-onset strain=18.23 %).
Designing new acceptors is critical for intrinsically stretchable organic solar cells (IS-OSCs) with high efficiency and mechanical robustness. However, nearly all stretchable polymer acceptors exhibit limited efficiency and high-performance small molecular acceptors are very brittle. In this regard, we select thienylene-alkane-thienylene (TAT) as the conjugate-break linker and synthesize four dimerized acceptors by the regulation of connecting sites and halogen substitutions. It is found that the connecting sites and halogen substitutions considerably impact the overall electronic structures, aggregation behaviors, and charge transport properties. Benefiting from the optimization of the molecular structure, the dimerized acceptor exhibits rational phase separation within the blend films, which significantly facilitates exciton dissociation while effectively suppressing charge recombination processes. Consequently, FDY-m-TAT-based rigid OSCs render the highest power conversion efficiency (PCE) of 18.07 % among reported acceptors containing conjugate-break linker. Most importantly, FDY-m-TAT-based IS-OSCs achieve high PCE (14.29 %) and remarkable stretchability (crack-onset strain [COS]=18.23 %), significantly surpassing Y6-based counterpart (PCE=12.80 % and COS=8.50 %). To sum up, these findings demonstrate that dimerized acceptors containing conjugate-break linkers have immense potential in developing highly efficient and mechanically robust OSCs.
Publication date: 15 June 2024
Source: Nano Energy, Volume 125
Author(s): Jing Li, Chenyang Zhang, Xiaokang Sun, Han Wang, Hanlin Hu, Kai Wang, Mingjia Xiao
By successive changes in molecular configuration and branching position of alkoxy side chains, we designed and synthesized a completely non-fused acceptor, TBT-26, with a narrow band gap of 1.38 eV and excellent stability. TBT-26 has a significantly low raw material cost of about 12 $/g. The TBT-26-based device gives outstanding power conversion efficiency of 17.0 % for small area device and 14.3 % for large area module with an area of 28.8 cm−2.
To meet the industrial requirements of organic photovoltaic (OPV) cells, it is imperative to accelerate the development of cost-effective materials. Thiophene-benzene-thiophene central unit-based acceptors possess the advantage of low synthetic cost, while their power conversion efficiency (PCE) is relatively low. Here, by incorporating a para-substituted benzene unit and 1st-position branched alkoxy chains with large steric hindrance, a completely non-fused non-fullerene acceptor, TBT-26, was designed and synthesized. The narrow band gap of 1.38 eV ensures the effective utilization of sunlight. The favorable phase separation morphology of TBT-26-based blend film facilitates the efficient exciton dissociation and charge transport in corresponding OPV cell. Therefore, the TBT-26-based small-area cell achieves an impressive PCE of 17.0 %, which is the highest value of completely non-fused OPV cells. Additionally, we successfully demonstrated the scalability of this design by fabricating a 28.8 cm2 module with a high PCE of 14.3 %. Overall, our work provides a practical molecular design strategy for developing high-performance and low-cost acceptors, paving the way for industrial applications of OPV technology.
