Chen Weijie

Publication date: April 2023

Source: Journal of Energy Chemistry, Volume 79

Author(s): Ning Su, Jianhua Chen, Mengran Peng, Guoping Li, Robert M. Pankow, Ding Zheng, Junqiao Ding, Antonio Facchetti, Tobin J. Marks

Ascorbic acid is proposed to suppress the formation of superoxide (O₂ ⁻) for high-performance tin solar cells. A complex is formed between Cs_0.05FA_0.95SnI₃ perovskite and ascorbic acid via strong hydrogen bonding interactions and it reduces Sn⁴⁺ to Sn²⁺ by CC double bonds. Finally, a power conversion efficiency (PCE) of 13.32% with a stability of 500 h is achieved based on Cs_0.05FA_0.95SnI₃ perovskite.

Power conversion efficiency (PCE) and stability of tin perovskite solar cells (TPSCs) are major concerns in developing lead-free photovoltaics. Photovoltaic performance of TPSCs often suffers from the oxidation of Sn²⁺, organic degradation, and ion migration, which inevitably cause plenty of trap states and render inferior device parameters. Herein, a natural ascorbic acid is first introduced for high-performance TPSCs as a multifunctional reductant to suppress the oxidation of Sn²⁺ and regulate trap states accordingly. Interestingly, it is found that the ascorbic acid reduces Sn⁴⁺ to Sn²⁺ by CC double bonds and forms a complex with Cs_0.05FA_0.95SnI₃ perovskites via strong hydrogen bonding interactions. By virtue of theoretical calculations, the mechanism of the ascorbic acid role is further clarified. Apart from effective passivation and suppressing trap density, a superoxide interaction between perovskite and ascorbic acid is proposed. The existence of ascorbic acid successfully improved the energy barrier for O₂ ⁻ generation. As a result, a significantly improved PCE from 8.95% to 13.32% is achieved for Cs_0.05FA_0.95SnI₃ TPSCs with 0.5% ascorbic acid incorporation under AM 1.5 G illumination. In addition, our devices maintain 90% value of initial PCE after 500 h storage.

A natural product, D-Aspartic acid, is applied as an additive for perovskite solar cells which effectively improves film morphology and passivates the defects of the perovskite, thus greatly enhancing the power conversion efficiency (PCE) and stability of the device.

Perovskite solar cells (PSCs) are widely studied as the most promising photovoltaic technology, but their performance is sensitive to the morphology and the defect density of the perovskite films. Herein, additive engineering strategy is applied to further improve the film morphology and device performance by doping a small amount of natural product, D-Aspartic acid (D-2-Aminobutanedioic acid, D-Asp), into perovskite precursor solution. The modified device exhibits a greatly enhanced power conversion efficiency of 22.7%, which is unprecedented for PSCs doped with natural amino acids, and 3000 h stability in ambient air is achieved. Through systematical characterizations, it is concluded that D-Asp could result in thicker film formation, outstanding perovskite film morphology, and reduced defect sites passivated by the multiple functional groups. The results prove that the performance and stability of the state-of-the-art mixed ion PSCs with regular architecture could be effectively enhanced by D-Asp. The minimum usage of the natural product as an additive is beneficial for the fabrication process and cost-control in the industrialization of PSCs. This work also highlights the different passivating mechanisms for the molecules with multiple functional groups which are meaningful for materials design.

With the proposed strategy via dispersing a liquid crystal small molecule BTR-Cl into the nonfullerene acceptor-rich domain, the donor-dispersed planar heterojunction (DD-PHJ) solar cells receive optimal vertical phase separation and effective charge transfer, considerable boost in the photovoltaic efficiency (18.21%), which is one of the best efficiencies among the values reported on nonhalogenated solvent-processed organic photovoltaics.

Realization of state-of-the art efficiencies in organic photovoltaics (OPV) generally relies on using toxic halogenated solution processing to arrive at the desired nanomorphology and optoelectronic responses, whereas the photovoltaic performance in nonhalogenated solution (NHS)-based OPVs is yet nonsatisfactory, mainly related to the difficulty of morphological control. Herein, a conceptual approach of donor-dispersed planar heterojunction (DD-PHJ) for improving the regulation of phase morphology and photovoltaic behaviors in NHS-processed OPVs is proposed, afforded by dispersing an ordered liquid crystal guest donor BTR-Cl into the nonfullerene acceptor host with sequential film deposition. The combined investigation shows that the inclusion of BTR-Cl plays a regulatory role in enhancing the crystallization, intermolecular donor/acceptor miscibility, and homogeneity in the donor–acceptor phase separation along vertical direction, which is conducive to improved charge transfer and reduced photovoltage loss. Of importance, the described DD-PHJ approach is applicable to representative OPV material systems, leading to a champion efficiency of 18.21% in devices prepared with NHS. This work provides a promising prospect toward high-efficiency and green solution-processed OPV devices.

Abnormal coating, drying, and crystallization of perovskite films during module fabrication is caused by laser-scribing process (P1) of transparent conductive oxide, which changes surface morphology of the area around the P1 line, and induces nonuniform heating during near-infrared radiation annealing. By tuning laser recipes, modules are fabricated with a power conversion efficiency of 7.2% with an active area of 46 cm².

Large-area perovskite solar modules fabrication has been demonstrated with a rapid process of large-area slot-die coating, drying, and crystallization using near-infrared radiation in ambient air, in which the laser-scribing process is applied to fabricate the modules. However, defective coating of perovskite layer near laser-scribed P1 line which isolates the front electrode of transparent conductive oxide (TCO) results very low module efficiencies. Therefore, systematic study is conducted to investigate the root cause, mechanism and solution of the defective coating and crystallization of the perovskite layer. Scanning electron microscope, energy-dispersive X-ray spectroscopy, and atomic force microscopy are used to characterize the TCO film before and after P1 scribing. It is found that P1 laser-scribing process changes surface morphology of TCO at the area near P1 line, which decreases the surface wettability and results discontinuous coating of precursor solution near P1 lines. The absence of TCO material in the P1 trench induces nonuniform heating during NIR annealing step, which is verified by thermal analysis via numerical simulation. After tuning laser process recipes, a large module with an active area of 46 cm² is fabricated with a power conversion efficiency of 7.2% and geometry fill factor of 93.8%.

In this work, the zinc oxide films armored by ethylenediaminetetraacetic acid (EDTA) and its derivatives (EDTA-Na and EDTA-K) as the multifunctional interlayers are comprehensively explored to optimize SnO₂/CsPbI₂Br buried interface for low-temperature carbon-based inorganic perovskite solar cells. As a result, the optimized devices achieve the highest efficiency of 13.94%, along with enhanced moisture, thermal, and ultraviolet light stability.

Abstract

The charge recombination resulting from bulk defects and interfacial energy level mismatch hinders the improvement of the power conversion efficiency (PCE) and stability of carbon-based inorganic perovskite solar cells (C-IPSCs). Herein, a series of small molecules including ethylenediaminetetraacetic acid (EDTA) and its derivatives (EDTA-Na and EDTA-K) are studied to functionalize the zinc oxide (ZnO) interlayers at the SnO₂/CsPbI₂Br buried interface to boost the photovoltaic performance of low-temperature C-IPSCs. This strategy can simultaneously passivate defects in ZnO and perovskite films, adjust interfacial energy level alignment, and release interfacial tensile stress, thereby improving interfacial contact, inhibiting ion migration, alleviating charge recombination, and promoting electron transport. As a result, a maximum PCE of 13.94% with a negligible hysteresis effect is obtained, which is one of the best results reported for low-temperature CsPbI₂Br C-IPSCs so far. Moreover, the optimized devices without encapsulation demonstrate greatly improved operational stability.

A new 12-crown-4-based small organic semiconductor CDT is synthesized and introduced in spiro-OMeTAD and simultaneously at the perovskite/spiro-OMeTAD interface. The CDT-treated perovskite solar cell achieves a high efficiency of 22.88% with excellent long-term stability.

In conventional (n-i-p) perovskite solar cells (PSCs), spiro-OMeTAD is the most widely used hole-transporting material (HTM), which contributes to the current state-of-the-art efficiency. Suffering from the low conductivity, dopants such as LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and tBP are usually required to achieve excellent hole transport properties in spiro-OMeTAD. Nevertheless, the hygroscopicity and the migration of Li⁺ during device operation severely affect the device's stability. To address the aforementioned issue, a 12-crown-4-based organic semiconductor (CDT) is synthesized and applied in PSCs. Notably, CDT is simultaneously doped in spiro-OMeTAD and perovskite layer through the antisolvent method. In this way, the strong “host-guest” interaction between crown ether and Li⁺ effectively inhibits its migration both in the hole transporting layer (HTL) and at the perovskite/HTM interface. Furthermore, the carbazole diphenylamine group in CDT facilitates hole transport, and meanwhile improves the hydrophobicity of the HTL. In addition, CDT added into the perovskite layer is also able to passivate defects by interacting with the undercoordinated Pb²⁺. In light of the aforementioned advantages, the CDT-based device shows a high power conversion efficiency approaching 23%, with excellent long-term stability.

The roles of the degree of delocalization of anions in determining the doping kinetics and transport mechanism of organic hole conductors are investigated. Structural analysis reveals anion-modulated ion exchange kinetics determine the hole-transport mechanism and device photostability. The strategy of Li⁺ solvation is developed to promote ion exchange, enabling improvement of device efficiency and stability.

Abstract

Chemical doping of organic semiconductors enables significant progress in improving their optoelectronic performance. However, the correlation between doping counter ions and charge-transport mechanism has not been yet well-understood. In this study, it is discovered that the anion-dependent degree of delocalization (DOD) of lithium-based dopants significantly determines the doping kinetics as well as the conductivity of organic hole transport layer (HTL), leading to large variation in solar cell efficiency and device stability. Specifically, the incorporation of bis(pentafluoroethanesulfonyl) imide (PFSI⁻) as the anion with a high DOD results in one order of magnitude higher film conductivity and thus an elevated power conversion efficiency (PCE) exceeding 22.1%, much higher than the state-of-the-art lithium bis(trifluoromethane)sulfonimide (LiTFSI) (21.1%) and lithium hexafluorophosphate (LiPF₆) (20.0%). Moreover, the dopant LiPF₆ with a smaller DOD produces higher doping yield of HTL accompanied by stronger light-induced PCE fluctuation. Structural analysis reveals anion-modulated ion exchange kinetics determine the hole-transport mechanism and device photostability. To mitigate these detrimental effects, a versatile strategy of Li⁺ solvation is developed to modulate the anion dissociation, enabling simultaneous improvement of device efficiency and stability. This study elucidates an intriguing and generally applicable doping mechanism, and envisages a bright future to further developing efficient and stable organic electronics.

Nanocrystals (NCs) embedding is an emerging efficient strategy to address the interfacial issues related with long-term stability and photoconversion efficiency of perovskite solar cells. Present review systematically analyzes their specific functionality of the embedded NCs as efficient mediators for carriers dynamic modulation, crystallinity enhancement, defect passivation, light trapping, and stability enhancement.

Abstract

Interfacial loss arising from defect trapping, contact barrier, and energy level alignment in the emerged perovskite solar cells (PSCs), is one of the most important issues to address for both improved photoconversion efficiency and long-term operational stability. The recent endeavors on the interfacial embedding of nanocrystals (NCs) in desired locations of PSCs have shown great success in terms of eliminating the interfacial loss in PSCs, while there is a lack of review to summarize the advances of NCs embedding for improved carrier dynamics and inhibited environmental degradation. Present study systematically analyzes the recent achievements on the embedding of a series of NCs including carbon dots, perovskite NCs, II-VI semiconductor NCs, metal/alloy NCs, which are intentionally introduced in desired layers/interfaces of PSCs. The specific functionality of the NCs embedding including carrier dynamic modulation, crystallinity enhancement, defect passivation, light trapping, and stability enhancement are sorted out, according to the requirement of each layer in PSCs. Finally, the current challenges and future perspectives of NCs embedding for perovskite-based optoelectronic devices is outlook. The present study provides a guide for developing NCs-based additives for high-performance PSCs is believed.

A pre-thermal treatment strategy paves the way to further delicately fine-tune film morphology toward high-performance nonfullerene organic photovoltaics. It enhances absorption, reduces trap-assistant Shockley-Read-Hall recombination, suppresses the energetic disorder as well as facilitates charge extraction, which contribute to the extraordinary J _SC generated and in turn significantly improve power conversion efficiency.

Abstract

Finding an effective approach to suppress trap formation is a potential route for enhancing the performance of nonfullerene organic photovoltaic (NF-OPVs) devices. Here, an extraordinary short-circuit current density (J _SC) value of 32.65 mA cm^-2 is achieved, higher than the state-of-the art NF-OPVs reported, reaching a high power conversion efficiency (PCE) of 17.92%. This remarkable enhancement is exhibited through the fine-tuning of PEDOT:PSS/PM6:Y7 films and interface morphologies via applying the prethermal treatment approach (Pre-TT) to the devices, which exhibit J _SC and PCE enhancement of 21% and 8%, respectively, compared to the pristine devices. Accordingly, the dependence of the J _SC upon the Pre-TT approach through a range of morphological, optical, electrical, and advanced transient measurements is investigated. The Pre-TT-based films are found to possess optimal smooth blend morphology with better dispersity owing to reduced domain size. Moreover, the measurements show that the optimized treated devices present higher exciton dissociation probabilities and generation rate of the free charge carriers, showing an ideal balanced electron/hole mobility that reveals the J _SC and PCE enhancement. Hence, Pre-TT approach provides a facile passivation strategy that reduces the trap state density of the blend film, improves interface charge transfer, allows balanced electron/hole mobility, and thus promotes device performance.

Herein, the interest of sputtering power reduction during physical vapor deposition of the rear-side indium-based transparent conduction oxide (TCO) is investigated to reduce the In consumption in silicon heterojunction solar cells. Halving the supplied power allows for a TCO thickness reduction of 50% and shows similar performances to those made with the reference process.

Herein, the interest of a sputtering power reduction during physical vapor deposition (PVD) of the rear side indium-based transparent conduction oxide (TCO) is investigated to reduce the In consumption in silicon heterojunction (SHJ) solar cells. Halving the supplied power allows for a TCO thickness reduction of 50%. Process fine-tuning is shown to retain satisfying TCO electrical properties, thus preventing unwanted additional resistance losses despite the drastic reduction in TCO thickness. The produced SHJ solar cells with a 50% reduced TCO thickness show similar performances to those made with the reference process. Using thinner TCO layers at the cell backside is, however, found to come with a bifaciality penalty, which is discussed in detail.

Efficient light energy sensing/conversion application has close relevance to interfacial engineering. Herein, this study suggests the improvement interface defect quality by adding perylenediimide (PDI)-derivative layer (with different thickness conditions) between the electron transport layer and the cathode. Consequently, the effect of the PDI-derivative layer on the optoelectronic device's performance is closely observed by analyzing the charge dynamics.

To fabricate efficient light sensing/energy conversion devices, the interfacial defects in perovskite devices must be controlled. Herein, an organic-small-molecule intermediate layer (consisting of PDINN; N,N'-bis(3-(3-(Dimethylamino)propylaminropyl)perylene-3,4,9,10-tetracarboxylic diimide) perylene-3,4,9,10-tetracarboxylic diimide (C₄₀H₄₆N₆O₄)) is deposited between the upper electrode and intermediate layer of a sensing device. The PDI-derivative has symmetrical aliphatic amine groups at both ends. The effects of the interfacial defect cover layer on the performance of the perovskite device due to the chemical and structural specificity of PDINN are investigated. The performance characteristics are determined under different illuminance conditions.

The N-(hydroxymethyl) acrylamide(HAM)-incorporated CsPbBr₃ perovskite solar cell fabricated by a two-step method achieves a cutting-edge power conversion efficiency of 9.05% with excellent humidity and thermal stability via quality and energy-level alignment improvement and dual-defects passivation of perovskite film by employing a self-polymerization strategy of monomer additives with multifunctional groups.

The photovoltaic performance of perovskite solar cells (PSCs) is immensely related to the perovskite film quality, defect states density, and interfacial energy-level alignment. Herein, a self-polymeric monomer of N-(hydroxymethyl) acrylamide (HAM) with CC, CO, and –NH multifunctional groups is introduced in the preparation of a CsPbBr₃ film by a two-step method to regulate the crystallization process and band structure and simultaneously passivate the dual-ionic defects. The results show that the HAM monomer first undergoes a pre-polymerization in the CsBr precursor aqueous solution after preheating to retard the crystallization of CsPbBr₃, and subsequently a further polymerization occurs during the annealing of the perovskite film to load at grain boundaries and form the CO⋯Pb (Cs) Lewis acid–base coordination and N–H⋯Br hydrogen bonding. Consequently, a large-grained CsPbBr₃ film with low defect density and optimized band structure is fabricated to effectively suppress nonradiative recombination and accelerate carrier extraction and transport, delivering a champion power conversion efficiency of 9.05% for the HAM-incorporated CsPbBr₃ PSCs, which is much higher than 6.50% efficiency for the reference one. Furthermore, the unencapsulated device maintains over 92% of the initial efficiency after 30 days storage in air with 85% relative humidity or at 85 °C, exhibiting superior moisture and thermal durability.

A facile and effective GeSe₂ post-deposition treatment (GeSe₂-PDT) strategy is adopted to passivate deep trap and band-tail states in the heterojunction of Cu₂ZnSn(S,Se)₄ solar cells. The severe nonradiative carrier recombination at depletion region is greatly decreased after the GeSe₂-PDT, yielding larger open-circuit voltage and fill factor. Consequently, a higher power conversion efficiency of 12.22% is achieved.

Abstract

Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) has emerged as a promising photovoltaic material not only because of its environmentally benign and earth-abundant constituents, but also its outstanding photoelectronic properties. Unfortunately, the significant open-circuit voltage (V _oc) loss and inferior fill factor (FF) resulting from abundant nonradiative carrier recombination at depletion region has become a major obstacle for further improving device performance. Here, an effective strategy to passivate the deep trap and band-tail states in the heterojunction is proposed, by modifying the CZTSSe absorber layer with GeSe₂ post-deposition treatment. The results reveal that the Ge⁴⁺ can migrate into the front surface of the absorber, which plays an active role in suppressing the Cu_Sn deep defects and [2Cu_Zn+Sn_Zn] defect clusters, accordingly dramatically reducing severe interfacial nonradiative carrier recombination of CZTSSe photovoltaic device. Under optimal treatment conditions, the CZTSSe solar cell efficiency increases from 10.36% to 12.22%, mainly benefitting from the increasement of V _oc and FF.

A self-assembled monolayer composed of amphiphilic molecules as the interface layer to reduce the energy loss between the perovskite and hole transport layers is reported. A remarkable power conversion efficiency (PCE) of 20.4% for wide-bandgap perovskite solar cells is attained. Additionally, excellent performance in indoor photovoltaics and tandem solar cells, with respective PCEs of 38.7% and 23.2%, are realized.

Abstract

The applications of wide-bandgap (WBG) perovskite solar cells (PSCs) are limited by their subpar efficiency and stability due to their high density of defects, especially those at interfaces. Theoretical analyses suggest a monolayer of molecules, which is of minimum thickness and, hence, minimum resistance across the interface, possessing multifunctional groups and a permanent dipole, should effectively passivate the defects and minimize energy losses at interfaces. Herein, a self-assembled monolayer (SAM) composed of amphiphilic molecules is designed and assembled as the interface layer to reduce the energy loss and enhance interface coupling between the perovskite and hole transport layer. It is found that the SAM also builds a back surface field through a p-type doping effect, which promotes hole extraction and suppress the carrier recombination. Consequently, a remarkable power conversion efficiency (PCE) of 20.4% in parallel with a high open-circuit voltage up to 1.25 V is attained. Additionally, an indoor PCE of 38.7% is realized. Both are among the best in their respective categories. Moreover, an all-perovskite tandem solar cell is configured, presenting a decent PCE of 23.2%. This work emphasizes the significance of WBG PSCs for optoelectronic applications and indicates the eminent effects of SAMs for optimization of WBG PSCs.

Synergistic surface modification of mixed Sn–Pb perovskite films by the combination of piperazine and C₆₀ pyrrolidine tris-acid realizes narrow-bandgap solar cells with power conversion efficiencies up to 22.7% and substantially elongated stability.

Abstract

Interfaces in thin-film photovoltaics play a pivotal role in determining device efficiency and longevity. In this work, the top surface treatment of mixed tin–lead (≈1.26 eV) halide perovskite films for p–i–n solar cells is studied. Charge extraction is promoted by treating the perovskite surface with piperazine. This compound reacts with the organic cations at the perovskite surface, modifying the surface structure and tuning the interfacial energy level alignment. In addition, the combined treatment with C₆₀ pyrrolidine tris-acid (CPTA) reduces hysteresis and leads to efficiencies up to 22.7%, with open-circuit voltage values reaching 0.90 V, ≈92% of the radiative limit for the bandgap of this material. The modified cells also show superior stability, with unencapsulated cells retaining 96% of their initial efficiency after >2000 h of storage in N₂ and encapsulated cells retaining 90% efficiency after >450 h of storage in air. Intriguingly, CPTA preferentially binds to Sn²⁺ sites at film surface over Pb²⁺ due to the energetically favored exposure of the former, according to first-principles calculations. This work provides new insights into the surface chemistry of perovskite films in terms of their structural, electronic, and defect characteristics and this knowledge is used to fabricate state-of-the-art solar cells.

The new generation of all-small-molecule organic solar cells (ASM-OSCs) utilizing small-molecule donors and Y-series nonfullerene acceptors has shown great progress in recent years, which provides distinctly different scenery from fullerene- and ITIC-series-based ASM-OSCs. The materials design strategy, morphology formation mechanism, and potential challenges for ASM-OSCs are systematically summarized.

Abstract

The emerging Y-series nonfullerene acceptors (Y-NFA) has prompted the rapid progress of power conversion efficiency (PCE) of all-small-molecule organic solar cells (ASM-OSCs) from around 12% to 17%. The excellent PCE improvement benefits from not only the outstanding properties of Y-series acceptors but also the successful development of small-molecule donors. The short-circuit current density, fill factor, and nonradiative recombination are all optimized to the unprecedented values, providing a scenery that is obviously different from the ITIC-series based ASM-OSCs. In this review, OSCs utilizing small-molecule donors and Y-NFA are summarized and classified in order to provide an up-to-date development overview and give an insight on structure–property correlation. Then, the characteristics of bulk-heterojunction (BHJ) formation of ASM-OSCs are discussed and compared with that of polymer-based OSCs. Finally, the challenges and outlook on designing ground-breaking small-molecule donor and forming an ideal BHJ morphology are discussed.

Surface treatment of inorganic perovskite film by trifluoroacetamidine featuring chelation configuration and multiple fluorine atoms allows record power conversion efficiency of inorganic perovskite solar cells.

Abstract

Minimizing surface defect is vital to further improve power conversion efficiency (PCE) and stability of inorganic perovskite solar cells (PSCs). Herein, we designed a passivator trifluoroacetamidine (TFA) to suppress CsPbI_3−x Br _x film defects. The amidine group of TFA can strongly chelate onto the perovskite surface to suppress the iodide vacancy, strengthened by additional hydrogen bonds. Moreover, three fluorine atoms allow strong intermolecular connection via intermolecular hydrogen bonds, thus constructing a robust shield against moisture. The TFA-treated PSCs exhibit remarkably suppressed recombination, yielding the record PCEs of 21.35 % and 17.21 % for 0.09 cm² and 1.0 cm² device areas, both of which are the highest for all-inorganic PSCs so far. The device also achieves a PCE of 39.78 % under indoor illumination, the highest for all-inorganic indoor photovoltaic devices. Furthermore, TFA greatly improves device ambient stability by preserving 93 % of the initial PCE after 960 h.

Nature Photonics, Published online: 08 December 2022; doi:10.1038/s41566-022-01111-x

A 1,8-dichloronaphthalene-based volatile-solid-additive strategy is proposed to improve the commercial viability of organic photovoltaics based on oligothiophene small molecules, problem-solving the critical challenges of organic photovoltaics toward commercialization, providing an alternative solution to reduce the efficiency-stability-cost gap of organic photovoltaics, pushing organic photovoltaics closer to commercial realization.

Abstract

The commercial viability of all-small-molecule (ASM) organic solar cells (OSCs) requires high efficiency, long-term stability, and low-cost production. However, satisfying all these factors at the same time remains highly challenging. Herein, a volatile solid additive, namely, 1,8-dichloronaphthalene (DCN) is demonstrated to simultaneously enhance the power conversion efficiency (PCE) and the storage, thermal as well as photo stabilities of oligothiophene ASM-OSCs with concise and low-cost syntheses. The improved PCEs are mainly due to the DCN-induced morphology control with improved exciton dissociation and reduced non-geminate recombination. Notably, the PCE of 16.0% stands as the best value for oligothiophene ASM-OSCs and is among the top values for all types of binary ASM-OSCs. In addition, devices incorporating DCN have shown remarkable long-term stability, retaining over 90% of their initial PCE after dark storage aging of 3000 h and thermal or light stressing of 500 h. The findings demonstrate that the volatile-solid-additive strategy can be a simple yet effective method of delivering highly efficient and stable oligothiophene ASM-OSCs with excellent commercial viability.

The review discusses the stability of crystal structure, summarizes the factors affecting crystal stability, and analyzes the physical properties of crystals. Then, the preparation of tin-based perovskite devices is summarized and discussed in detail with respect to four aspects: thin film manufacturing processes, additive selection, preparation of low-dimensional structures and selection of interface layers.

Abstract

Metal halide perovskite solar cells (PSCs) have emerged as an important direction for photovoltaic research. Although the power conversion efficiency (PCE) of lead-based PSCs has reached 25.7%, still the toxicity of Pb remains one main obstacle for commercial adoption. Thus, to address this issue, Pb-free perovskites have been proposed. Among them, tin-based perovskites have emerged as promising candidates. Unfortunately, the fast oxidation of Sn²⁺ to Sn⁴⁺ leads to low stability and efficiency. Many strategies have been implemented to address these challenges in Sn-based PSCs. This work introduces stability and efficiency improvement strategies for pure Sn-based PSCs by optimization of the crystal structure, processing and interfaces as well as, implementation of low-dimension structures. Finally, new perspectives for further developing Sn-based PSCs are provided.

A molecular design principle of the third component is established to tackle the issue of excessive self-aggregation of Y6-derivatives during the film formation through crystallinity and miscibility regulation. With the addition of BTP-Th, the ternary device yielded a remarkable efficiency of 18.53 %, which is a significant improvement with regard to the efficiency of 17.22 % for the control reference binary device.

Abstract

On the premise of strongly crystalline materials involved, it is a challenge to control the phase separation of bulk-heterojunction donor/acceptor active layer to fabricate high-performance polymer solar cells (PSCs). Herein, we develop a molecular design strategy of the third component to synthesize three guest materials (namely BTPT, BTP-Th, and BTP-2Th) to address this issue. We investigate and reveal the effect of crystallinity and miscibility of the third component in controlling the phase separation of Y6-derivatives-based blend film. As a result, a remarkable power-conversion efficiency of 18.53 % is obtained in the ternary PSC based on PTQ10 : m-BTP-PhC6 with BTP-Th as the third component, which is a significant improvement with regard to the efficiency of 17.22 % for the control binary device. Our study offers a molecular design strategy to develop a third component for building ternary PSCs in terms of crystallinity and miscibility regulation.