吴晓晓

By employing a holistic optimization strategy to reduce the V _OC-deficit of the 1.77 eV wide-bandgap perovskite solar cells, the first proof-of-concept four-terminal all-perovskite flexible tandem solar cell with a power conversion efficiency of 22.6% is presented. When integrating into two-terminal flexible tandems, 23.8% flexible all-perovskite tandem solar cells with a superior V _OC of 2.1 V are achieved.

Abstract

Among various types of perovskite-based tandem solar cells (TSCs), all-perovskite TSCs are of particular attractiveness for building- and vehicle-integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power-to-weight ratio. However, the efficiency of flexible all-perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide-bandgap (WBG) perovskite solar cells on the flexible substrates as well as their low open-circuit voltage (V _OC). Here, it is reported that the use of self-assembled monolayers as hole-selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, a postdeposition treatment with 2-thiopheneethylammonium chloride is employed to further suppress the bulk and interfacial recombination, boosting the V _OC of the WBG top cell to 1.29 V. Based on this, the first proof-of-concept four-terminal all-perovskite flexible TSC with a power conversion efficiency of 22.6% is presented. When integrating into two-terminal flexible tandems, 23.8% flexible all-perovskite TSCs with a superior V _OC of 2.1 V is achieved, which is on par with the V _OC reported on the 28% all-perovskite tandems grown on the rigid substrate.

Publication date: 20 April 2022

Source: Joule, Volume 6, Issue 4

Author(s): Kai Wang, Luyao Zheng, Yuchen Hou, Amin Nozariasbmarz, Bed Poudel, Jungjin Yoon, Tao Ye, Dong Yang, Alexej V. Pogrebnyakov, Venkatraman Gopalan, Shashank Priya

Two novel dopant-free hole transport materials (HTMs) named Y6-T and Y-T with a large conjugated electron-deficient core are developed for efficient perovskite solar cells. The champion power conversion efficiency (PCE) reaches 20.29% for Y-T-based device. The Y-T-based devices without encapsulation retain over 90% of the initial PCE in air with a relative humidity around 30% after storing for 60 days.

Abstract

Hole transport materials (HTMs) play a significant role in device efficiencies and long-term stabilities of perovskite solar cells (PSCs). In this work, two simple dopant-free HTMs are designed with a large conjugated electron-deficient core. On the one hand, a large coplanar backbone endows enhanced π–π stacking and reduced hole hopping distance. On the other hand, the incorporation of electron-deficient unit can easily tune the energy levels as well as increase hole mobilities. Combining these two advantages together, 12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro[1,2,5]thiadiazole[3,4-e]thieno[2″,3″:4,5]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole is chosen as the large electron-deficient core to construct two novel dopant-free HTMs, Y6-T and Y-T. Both Y6-T and Y-T behave suitable highest occupied molecular orbital levels, good hole mobilities, as well as strong hydrophobicities. After careful device optimization with a passivation agent, Y-T delivers an impressive power conversion efficiency of 20.29%, which is higher than that of Y6-T (18.82%) and doped spiro-OMeTAD (19.24%). Moreover, PSCs based on Y6-T and Y-T show much better long-term stabilities than spiro-OMeTAD due to the intrinsic hydrophobicity. Therefore, this work provides a promising candidate as well as a useful design strategy for exploring dopant-free HTMs, which may pave the way for the commercialization of PSCs.

Hybrid perovskite with unsaturated organoammoniums is demonstrated to be able to undergo solid-state polymerization without damaging the perovskite structure. The polymerized perovskite behaves like a polymer with enhanced stability and flexi bility. The lattice rigidity is also enhanced due to the polymerized covalent CC bonding. As a result, a stable and efficient polymerized perovskite light-emitting diode with an external quantum efficiency (EQE) of 23.2% is demonstrated.

Abstract

The intrinsic soft lattice nature of organometal halide perovskites (OHPs) makes them very tolerant to defects and ideal candidates for solution-processed optoelectronic devices. However, the soft lattice results in low stability towards external stresses such as heating and humidity, high density of phonons and strong electron–phonon coupling (EPC). Here, it is demonstrated that the OHPs with unsaturated 4-vinylbenzylammonium (VBA) as organoammonium cations can be polymerized without damaging the perovskite structure and its tolerance to defects. The polymerized perovskites show enhanced stability and flexibility compared to regular three-dimensional and two-dimensional (2D) perovskites. Furthermore, the polymerized 4-vinylbenzylammonium group improves perovskite lattice rigidity substantially, resulting in a reduced non-radiative recombination rate because of suppressed electron–phonon coupling, and enhanced carrier mobility because of suppressed phonon scattering. 2D polymerized perovskite light-emitting diodes (PeLEDs) with strong electroluminescence at room temperature, and quasi-2D PeLEDs with an external quantum efficiency (EQE) of 23.2% and enhanced operation stability are demonstrated. The work has opened a new way of enhancing the intrinsic stability and optoelectronic properties of OHPs.

The electron transport layer (ETL) plays a crucial part in extracting electrons and optimizing interfacial contact for perovskite solar cells (PVSCs). Herein, the EVA is introduced into PC₆₁BM to promote the orderly molecular stacking of ETLs. The PC₆₁BM:EVA-based MAPbI₃ PVSCs deliver a champion efficiency of 19.32% and regain 80% of initial efficiency after storage under 52% humidity for 1500 h.

Abstract

The electron transport layer (ETL) plays a crucial part in extracting electron carriers while optimizing the interfacial contact of perovskite/electrode in planar heterojunction perovskite solar cells (PVSCs). Despite various ETLs being designed for efficient PVSCs, there exists hardly any research on the effect of molecular stacking order on device performance. Herein, poly(ethylene-co-vinyl acetate) (EVA) is employed as the [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) solution additive. The strong binding energy between EVA with PC₆₁BM promotes the molecular stacking order of ETLs, which alleviates the morphology inhomogeneity, possesses a matched energy level, blocks ion migration, and improves the water–oxygen barrier of perovskite devices. The blade-coated MAPbI₃-based PVSCs achieve a power conversion efficiency (PCE) of 19.32% with positive reproducibility and negligible hysteresis, as well as maintain 90% and 80% of the initial PCE after storage under inert and ambient conditions (52% humidity) for 1500 h without encapsulation. This strategy also improves the champion PCE of CsFAMA-based PVSCs to 20.33%. These findings demonstrate that the regulation of molecular stacking order is a valid approach to optimize interfacial charge-carrier recombination in PVSCs, which meet the demand for high-performance ETL in large-area PVSCs and improve the upscaling of the fabrication technology toward practical applications.

To understand the nature of hysteresis, theoretical mechanisms and experimental measurements are provided based on a combination of first-principles simulations, cross-section scanning electron microscopy images, and time-dependent photocurrent measurements. The defect assistance ion-migration process could be the primary contribution to hysteresis. The defect density is reduced via the in situ passivation of PbI₂ crystals, which prevents the migration of ions effectively, and the hysteresis index is decreased from 22.43% to 1.04%.

Abstract

As one of the most promising photovoltaic materials, the efficiency of inorganic–organic hybrid halide perovskite solar cells (PSCs) has reached 25.5% in 2020. However, the stability and hysteresis remain primary challenges before it can become a commercial photovoltaic technology. Therefore, those issues have drawn significant attention for photovoltaic applications. In this work, a study of the PSCs hysteresis improvement is presented based on a combination of first-principles simulations, scanning electron microscopy images, and time-dependent photocurrent measurements. It indicates the hysteresis led by the ion migration and accumulation is mainly localized at the two interfaces: one is between electron transport layer and active layer, and the other is between active layer and hole transport layer. Considering the massive defects at the grain boundaries (GBs), they lower the potential barriers significantly. The defect density at GBs is therefore reduced via the in situ passivation of PbI₂ crystals. The hysteresis index is decreased from 22.43% down to 1.04%, and results in an improvement in efficiency from 17.12% up to 20.10%. Following the understanding of defect-induced hysteresis, an approach to improve the hysteresis is provided, which can be integrated into the fabrication process and widely applied to enhance the performance of PSCs.

A sputtered NiO _x seed layer is employed to promote the adsorption of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayers. The resulting high-density MeO-2PACz provides an increased passivation, an enhanced hole-selectivity, a favorable energy-level alignment, and a robust physical contact between perovskite and indium tin oxide. The corresponding inverted perovskite solar cell exhibits an impressive efficiency of 19.9%.

Self-assembled monolayers (SAMs) have emerged as effective carrier transport layers in perovskite (PVK) solar cells because of their unique ability to manipulate interfacial property, as well as simple processing and scalable fabrication. However, the defects and pinholes derived from their sensitive adsorption process inevitably deteriorate the final device performance. Herein, a sputtered nickel oxide (NiO _x ) interlayer is used as a seed layer to promote the adsorption of the [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) SAM on the indium tin oxide (ITO) substrate. The promoted adsorption is attributed to the enhanced tridentate binding between MeO-2PACz and NiO _x relative to the conventional bidentate binding between MeO-2PACz and ITO. In addition, the NiO _x modification can simultaneously improve the passivation ability and hole-selectivity of the MeO-2PACz, provide a favorable energy-level alignment at the ITO/PVK interface, and prevent a direct contact between PVK and ITO. As a consequence, this NiO _x -seeded MeO-2PACz hole transport layer enables a significantly enhanced power conversion efficiency of 19.9% in comparison with 18.4% of the control device. This work provides an effective strategy to improve the performance of the SAM-based photoelectric device.

High-quality (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I₀.₈₃Br_0.17)₃ perovskite films are fabricated by solvent volatilization. This method does not need an antisolvent technique and presents significant potential for large-scale and large-area device fabrication. A high power conversion efficiency of 20.6% is obtained by the films. A large area perovskite film of 10 × 10 cm² can be fabricated by the method.

Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.83Br_0.17)₃ (CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI _x Cl _y Br _z during annealing, leading to high-quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing-incidence wide-angle X-ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large-scale production.

Herein, a systematic overview of commercialization of perovskite PV technology is provided, including module architecture, laser scribing, cost, and life cycle. The key strategies for fabrication, stability, and performance are also discussed. In addition, the current issues and future perspective are provided toward commercialization of perovskite solar modules in the near future.

The commercialization of perovskite photovoltaic technology is dependent on the development of high-efficiency, stable, and large-area solar modules. Despite the rapid rise in efficiencies of laboratory-scale perovskite solar cells (PSCs), there is still a big gap in the transition from small-area devices to large-area perovskite solar modules (PSMs). Herein, recent progresses on scaling-up PSMs are reviewed: first, multifarious scalable preparation methods, solvent engineering, and corresponding morphology control strategies for large-area homogeneous perovskite films are summarized. Various charge carrier transport materials, electrode materials, and their scaling methods for high-efficiency and stable PSMs are then outlined and the device structure design of PSMs is discussed. Finally, the current strategies for optimizing the environmental stability of devices are highlighted, and packaging for reducing lead leakage during operation is discussed.

The low-cost, scalable, and high-performing ZnOSnO₂ cascaded electron transport layer based on spray coating and blade coating is developed and demonstrates the superior advantages in electrons’ extraction, energy band matching, interface stability, and crystallization tailoring for perovskite films. Further combined with the same scalable blade-coated perovskite film and hole transport layer, efficient planar modules with high reproducibility are facilely realized.

Perovskite solar cells are the fastest-growing photovoltaic technology in recent years. However, together with the stability, the low-cost and high-quality preparation of large-area modules still limits their commercialization process. Herein, a scalable and high-performance ZnOSnO₂ cascade double-layer electron transport layer (ETL) for efficient and stable perovskite modules is reported. The cascaded ETL is fabricated using a simple spray pyrolysis coating combined with the blade coating process, which not only effectively improves the interface stability by avoiding the protonation of ZnO to maintain its high electron mobility, but also provides a much smoother surface for the crystallization of perovskites. In addition, the well-matched conduction band level between SnO₂ and perovskites ensures the improvement of open-circuit voltage. Subsequently, combined with the blade-coated perovskite layer and hole transport layer film, large-area planar perovskite modules are successfully prepared. These high-quality films enable the perovskite solar modules to achieve impressive efficiencies of 17.8% in the module size 6 × 6 cm² and 16.6% in a size of 10 × 10 cm². The obtained module also shows excellent reproducibility and stability. The high-performance ETL and the related deposition method developed in this work are promising for applications in the industrial scalable perovskite modules’ fabrication.

A library of 2D and quasi-2D halide perovskite lateral heterostructures is synthesized, and the platform is utilized to analyze the impact of organic cation and inorganic layer thickness on bromide–iodide interdiffusion kinetics. This quantitative halide diffusion study on perovskites will aid in driving future innovations toward novel material design and optoelectronic device applications.

Abstract

Anionic diffusion strongly impacts the stability of halide perovskite materials, but it is still not well understood. Here, a quantitative investigation of in-plane thermally driven anionic inter-diffusion in a series of novel 2D and quasi-2D halide perovskites lateral heterostructures is reported. The calculated diffusion coefficients (D) reveal the inhibition of Br–I inter-diffusion with bulky π-conjugated organic cations compared with short-chain aliphatic organic cations. Furthermore, halide diffusion is found to be faster in quasi-2D (n > 1) than 2D perovskites (n = 1). The increment becomes less apparent as the “n” number increases, akin to the quantum confinement effect observed for band gaps. These trends are rationalized by molecular dynamics simulations of free energy barriers for halide diffusion that reveal mechanisms for suppressing diffusion. This work provides important fundamental insights on the anionic migration and diffusion process in halide perovskite materials.

Towards stable solar cells, ferrocene as a perpetual recovering agent has been developed to fix all elemental defects in ABX₃ perovskite by a chain-reaction cycle. The ferrocene cations can form a 1D perovskite structure which has suitable dissociation energy to convert back to light-harvesting 3D perovskite and reactivate its photovoltaic performance. Based on this recovering agent, perovskite solar cell can achieve >10 000 h lifetime.

Abstract

Lead halide perovskites always emerge complex interactions among different elemental ions, which lead to multiple intrinsic imperfections. Elemental defects, such as amine, Pb, and I vacancies at A-, B-, and X-sites, are main issues to deteriorate perovskite solar cells (PSCs). Unfortunately, most previous passivators can only temporarily fix partial inactive vacancies as sacrificial agents. Herein, we propose a recovery agent, ferrocene (Fc), which can form a one-dimensional perovskite with adequate steric cavities and suitable dissociation energy to recover all elemental defects back to active light-harvesting perovskites, and regenerate Fc itself meanwhile. Based on this perpetual chain-reaction cycle, corresponding PSCs maintain >10 000-hour lifetime in inert condition and >1000-hour durabilities under various extreme environments, including continuous 85 °C heating, 50 % relative humidity wetting, and 1-sun light soaking.

One-step antisolvent-free hot-coating method is successfully used to fabricate Sn–Pb perovskite solar cells (PSCs) for the first time. Multiple cations are introduced to control the crystallization of the Sn–Pb film which produces PSCs with a champion power conversion efficiency over 15% and robust shelf stability. A novel ecofriendly approach for the fabrication of Sn–Pb PSCs is provided.

Pb-based perovskite solar cells (PSCs) have shown great potential in next-generation photovoltaics. However, the toxicity of Pb remains a big concern. Partial replacement of Pb with Sn is shown to reduce the toxicity of PSCs without considerably compromising the device performance. Currently, Sn–Pb single-junction PSCs have realized a champion power conversion efficiency (PCE) of 21.7%, whereas all perovskite tandem PSCs with a Pb–Sn device as the bottom cell have achieved a PCE of 25.5%. However, the fabrication process of Sn–Pb PSCs is still not ecofriendly due to the use of hazardous organic solvents and antisolvents. Herein, for the first time, a one-step antisolvent-free method is developed to fabricate a high-quality Sn–Pb perovskite film using methylammonium acetate (MAAc) ionic liquid as a green solvent. The crucial effects of multiple organic halides (MOHs) on the crystallization process and characteristics of the Sn–Pb film are comprehensively investigated. After optimizing the film fabrication parameters, PSCs with a champion PCE of 15.42% can be achieved. Moreover, the device exhibits robust stability that shows negligible PCE loss after being stored in N₂ for 720 h. A new avenue to promote the ecofriendly fabrication of efficient Sn–Pb PSCs is opened up.

The polydimethylsiloxane (PDMS)/Al₂O₃ multilayered encapsulation films with distinct interfaces are obtained by exposing the PDMS sublayer to the O₂ plasma. Besides, the epoxy layer helps improve the flexibility of the barrier further by adjusting the neutral axis position. The lifespan of the OLEDs encapsulated with the multilayered structure is around 60 times longer than that of the pristine ones.

Abstract

In this work, the polydimethylsiloxane (PDMS)/Al₂O₃ nanolaminates with optimized sublayer thickness and interfaces have been developed to protect the organic light-emitting didoes (OLEDs) from the erosion of the moisture in the ambient. The O₂ plasma pretreatment is used to tune the wettability of the ultrathin PDMS sublayers with nanoscale thickness, and the distinct interfaces between the Al₂O₃ and PDMS sublayers are obtained. The electrical calcium test is exploited to evaluate the barrier properties of the encapsulation nanolayers, and the water vapor transmission rate (WVTR) value of the 2.5 PDMS/Al₂O₃ dyads can reach the range of ≈10⁻⁵ g m⁻² day⁻¹. The mechanical stability of the nanolaminates is further improved by introducing the top epoxy layer, which helps move the neutral axis (NA) to the center of the barrier, and the applied external strain decreases significantly. Compared with the sample without the epoxy layer, a slighter increase of the WVTR value of the multilayered encapsulation films with optimized NA position is obtained. Furthermore, the operational lifetime of blue OLEDs encapsulated with the multilayered encapsulation films improves from 6 to more than 370 h, which shows significantly improved stability and reliability.

Near-infrared (NIR) photoactive semiconductor quantum dots (QDs) play a critical role for designing efficient wide-spectrum solar cells. This review provides a comprehensive analysis of the latest achievements of NIR QDs used for solar cells, including the classification of QDs and their photovoltaic performance, various strategies for performance improvements, and the challenges and perspectives for the future advances.

Abstract

Semiconductor quantum dots (QDs) are nanocrystals whose excitons are bound in 3D space. Owning to their remarkable quantum confinement effect, QDs exhibit a discontinuous electronic energy level structure similar to that of atoms, leading to novel physical, optical, and electrical properties for various optoelectronic device applications including solar cells. Near-infrared photoactive narrow bandgap (NBG) QDs can maximize the use of solar energy through the quantum size effect, offering a good opportunity for designing highly efficient wide-spectrum responsive solar cells. This review analyzes the recent research progress of NBG QDs as light absorbing materials in solar cells. The critical elaboration of the latest achievements both in material design and device optimization for NBG QD-based solar cells (QDSCs), including QD synthesis and film fabrication, design of device configuration, classification of NBG QDs and their photovoltaic performance, strategies for performance improvements is focused upon. The current challenges and perspectives for the further advance of NBG QDSCs are also discussed.

Gradual perovskite phase based on 2D cyclohexylmethylammonium iodide as the order of n and funnel-like energy level alignment during surface treatment with a simple solution process facilitates efficient charge transport electrically and improves power conversion efficiency from 20.41% to 23.91%.

Abstract

Insufficient charge extraction at the interfaces between light-absorbing perovskites and charge transporting layers is one of the drawbacks of state-of-the-art perovskite solar cells. Surface treatments and/or interface engineering are necessary to approach the Shockley–Queisser limit. In this work, novel 2D layered perovskites, such as CHA₂PbI₄ (CHAI = cyclohexylammonium iodide) and CHMA₂PbI₄ (CHMAI = cyclohexylmethylammonium iodide), are introduced in between 3D perovskites and hole transporting layers by a simple solution process and the 2D/3D perovskite heterojunction is formed and confirmed. Spontaneous photoluminescence quenching is observed by efficient hole extraction with a favorable valence band alignment. The charge extraction ability and recombination are directly measured by the transient photocurrent and photovoltage. Moreover, the interface resistance of the devices significantly is decreased to 30% as compared to devices without 2D perovskites. As a result, the devices with 2D/3D perovskite heterojunction exhibit improved power conversion efficiency (PCE) from 20.41% to 23.91% primarily because of the increased open-circuit voltage (1.079 to 1.143 V) and fill factor (78.22% to 84.25%). The results provide a detailed insight into hole extraction and high PCEs with the formation of a 2D/3D perovskite heterojunction.

A poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS)-free organic solar cell (OSC) architecture is successfully constructed by employing a binary solvent-chlorinated indium tin oxide anode, which can simultaneously improve the device performance and operational stability of non-fullerene OSCs.

Abstract

Despite the tremendous development of different high-performing photovoltaic systems in non-fullerene polymer solar cells (PSCs), improving their performance is still highly demanding. Herein, an effective and compatible strategy, i.e., binary-solvent-chlorinated indium tin oxide (ITO) anode, is presented to improve the device performance of the state-of-the-art photoactive systems. Although both ODCB (1,2-dichlorobenzene) solvent- and ODCB:H₂O₂ (hydrogen peroxide) co-solvent-chlorinated ITO (ITO-Cl_-ODCB and ITO-Cl_-ODCB:H2O2) show similar optical transmittance, electrical conductivities, and work function values, ITO-Cl_-ODCB:H2O2 exhibits higher Cl surface coverage and more suitable surface free energy close to the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-buffered ITO anode (ITO/PEDOT:PSS). As a direct consequence, the performance of ITO-Cl_-ODCB-based PBDB-T-2F:BTP-eC9:PC₇₁BM PSCs is comparable as the bare ITO-based devices. In contrast, the performance of ITO-Cl_-ODCB:H2O2-based devices with both small and the scaled-up areas significantly surpass the ITO/PEDOT:PSS-based devices. Furthermore, detailed experimental studies are conducted linking optical property, blend morphology, and physical dynamics to find the reasons for the performance difference. By applying the ITO-Cl_-ODCB:H2O2 anode to six other photovoltaic systems, the device efficiencies are enhanced by 3.6–6.2% relative to those of the ITO/PEDOT:PSS-based control devices, which validates its great application potential of co-solvent-modified ITO anode employed into PEDOT:PSS-free PSCs.

Metal-based nanomaterials have gradually come into focus in the context of ultrafast photonics due to their outstanding optical properties. The state of the art of metal-based nano materials in fabrications, optical pro perties, and applications as saturable absorbers are summarized in this review, aiming to accelerate the exploration of nanomaterials and further stimulate the applications in various fields.

Abstract

Nanomaterials have demonstrated excellent mechanical, thermal, optical, and electrical properties in various fields, including 1D carbon nanotubes, as well as 2D materials starting from graphene. Metal-based nanomaterials, mainly divided into metal and metal oxide nanoparticles, also gradually come into the sight of ultrafast photonics applications due to the outstanding optical properties. The optical properties of metal nanoparticles can be enhanced by the interaction between conduction electrons with electric fields that is called surface plasmon resonance. As for metal oxide nanoparticles, optical properties are closely related to bandgap structures. When it comes to transition metal oxides, other phenomena also play important roles in optical absorption such as spin inversion and excitons of iron. Moreover, preparation methods of materials are also crucial for their properties and further applications. Therefore, in this review, commonly used physical and chemical fabrication methods for metal-based nanomaterials are first introduced. Then the optical properties of typical metal and metal oxide nanoparticles are discussed specifically. In addition, the applications of metal-based nanomaterials in ultrafast lasers based on mode-locked and Q-switched techniques are also summarized. Finally, a summary and outlook toward the synthesis, optical properties, and applications in ultrafast photonics of metal-based nanomaterials are presented.