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Unique c-MoS2 nanosheets with corrugated edges mitigate the suppression of LiPSs and assist to reutilize them to boost the electrochemical kinetics in the Li–S battery.

A polymer-based hole-transporting layer (HTL) with a tunable work function and highest occupied molecular orbital (HOMO) position was demonstrated to effectively optimize the anode junctions of optoelectronic devices. Herein, the perfluorinated ionomer (PFI) was utilized to realize the synthesis of a well-dispersed poly(3,4-ethylene dioxythiophene) (PEDOT) colloid solution, which could be subsequently cast into an efficient HTL. According to the time-of-flight secondary-ion mass spectroscopy and ultraviolet photoelectron spectroscopy analysis, a uniform, interpenetrating PEDOT network with a deep-lying HOMO position could be obtained in the PEDOT:PFI layer. For solar cells, since a deep-lying HOMO position of the HTL was favorable for minimizing the hole injection barrier, a superior organic photovoltaic efficiency of 15.1% and a perovskite solar cell efficiency of 17.8% were achieved. As for organic photodetectors, a deep-lying HOMO position of the HTL was able to reduce the dark current density (JD) by blocking the leakage current under a reverse bias. Utilizing the PEDOT:PFI with an optimized PFI content, an extremely low JD of 6.2 nA cm−2 with an external quantum efficiency of 67% at 1000 nm wavelength was achieved, which sets a benchmark for the emerging near infrared sensing technologies.

Technological implementation of organolead trihalide perovskite (OTP) photovoltaics requires suppression of the surface ionic defects and grain boundaries of OTP films. These surface ionic defects have a detrimental effect on the power conversion efficiency (PCE), are notorious for introducing hysteresis into the current density–voltage (J–V) characteristics, and decrease the stability of perovskite solar cells (PSCs). Here, we report the use of core/shell quantum dots (QDs) as passivation layers on the OTP surfaces to decrease the trap density and, simultaneously, stabilize the OTP chemical structure and extend the charge carrier lifetime. Density functional theory (DFT) calculations indicated that the OTP surface defects and grain boundaries were effectively suppressed by the presence of the CdSe/ZnS QDs. We attribute the lower trap density of the OTP to the Se2− anions from the CdSe/ZnS passivation layer, inducing van der Waals interactions between the organic and inorganic components of the framework. For PSCs featuring CdSe/ZnS QD passivation, the PCE reached close to 20% with diminishing hysteresis of the J–V characteristics and fill factor (FF) of 81.44%. Moreover, the PSCs incorporating the CdSe/ZnS QD passivation layer exhibited long-term stability, retaining 75 and 80% of their initial performance after 2400 and 720 h, respectively. This facile interfacial strategy appears highly applicable for preparing high-performance durable OTP-based high optoelectronic devices.

Over the past decade, intensive research efforts have been directed toward the field of organic–inorganic hybrid perovskites, with dramatic progress made in both the photovoltaic performance and device stability. Therefore, it has become the fastest growing photovoltaic research area. Perovskite materials use low-cost earth-abundant elements and can be solution-processed; furthermore, the technology is compatible with large-scale roll-to-roll manufacturing. Recently, the successful demonstration of the photovoltaic performance of perovskites reaching that of the commercialized monosilicon photovoltaic technology combined with the significantly improved stability has made scaling-up the perovskite PV technology to become a new research area, which is the topic of this review. First, the fundamental background knowledge of classical nucleation and crystal growth from a solution is summarized along with its application in perovskite film evolution. We then discuss the common perovskite PV device architectures and perovskite layer deposition methods, followed by summarizing scalable solution approaches with recent progress and related challenges for the scaling-up process. Upon the introduction of the current in-depth understanding of perovskite nucleation and crystal growth, external strategies (including both physical and chemical approaches) controlling the perovskite film formation are reviewed in diverse scalable manufacturing methods. Overall, aiming at overcoming the challenges of transferring from laboratory research, we provide an overview of achieving high-performance perovskite solar cells by using scalable fabrication methods via precise nucleation and crystal growth control during the perovskite film formation process.

Cost effective imidazole-based star-shaped oligo(arylamines) were easily prepared in good yields via the reaction of one precursor containing two or more aldehydes with a dione compound having two arylamines. High performance perovskite (MAPbI3) solar cells with a conventional cell configuration were fabricated using these compounds as dopant-free hole transport materials. The best solar-to-electricity conversion efficiency reached ∼17.5%, which surpassed that based on LiTFSI/t-BP doped spiro-OMeTAD. The cell also exhibited much better temporal stability than the standard cell of LiTFSI/t-BP doped spiro-OMeTAD, as no hydrophilic dopants are needed.

Anatase titanium dioxide (an-TiO2) is often used as the electron transporting material (ETM) in planar-heterojunction perovskite solar cells (PSCs) because of its excellent semiconductor characteristics, outstanding optical transmittance, and suitable band structure. Herein, we report an inexpensive method for mass-scale production of TiO2 ETMs at room temperature (RT ∼ 30 °C), involving the grinding of large clumps of an-TiO2 to form a suspension of TiO2 nanoparticles (NPs) in isopropyl alcohol for meso-superstructured PSCs. This process does not involve any chemical synthesis; it is a purely physical process. The lowest unoccupied molecular orbital (LUMO) of ground an-TiO2 NPs, estimated using ultraviolet photoelectron spectroscopy (UPS), was ca. 4.06 eV, which is a salient feature for the active layer. A regular perovskite solar cell (PSC) based on a CH3NH3PbI3 absorber and ground an-TiO2 ETL exhibited a champion power conversion efficiency (PCE) of 17.43% with an active area of 0.1 cm2. The same ground an-TiO2 NPs were used to fabricate a large-area (designated area: 25.2 cm2) PSC and a PCE of 14.19% was achieved. PSC devices incorporating the ground an-TiO2 NP ETLs exhibited an attractive long-term device stability, with the PCE retaining approximately 85% of the initial values after 80 days.

The main issues in planar perovskite solar cells are the coverage and crystallinity of the perovskite film on the PEDOT:PSS layer. To enhance these features, we introduced alkali metal halides (salts) as additives into the perovskite precursor solution used in a two-step preparation method. These alkali metal halides chelate with Pb2+ ions and enhance the crystal growth of PbI2 films, resulting in nanostructured morphologies. The nanostructured PbI2 films promote homogeneous nucleation and larger crystallite sizes, thereby enhancing the morphology and crystallinity of the perovskite films. The alkali metal halides recrystallize the small grains and passivate the grain boundaries and interface states, allowing effective charge generation and dissociation in perovskite films. Photoluminescence measurements indicated that perovskite films prepared with salt additives featured fewer charge traps and defects. The power conversion efficiency of the device incorporating a small amount of a salt additive increased by approximately 33%—from 11.4 to 15.08%. This device was more stable than a corresponding device prepared without the additive, with only 16.5% degradation occurring over a period of 50 days.

Replacing toxic halogenated solvents with eco-friendly solvents will be necessary for the upscaling and mass production of organic photovoltaics (OPVs). In this study, toluene (Tol), a halogen-free solvent, was employed in the fabrication of molecular solar cells, achieving a power conversion efficiency (PCE) higher than that obtained when using a chlorinated counterpart, chloroform (CF). SMPV1, a two-dimensional conjugated small molecule, was used as the donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor to form bulk heterojunction (BHJ) OPVs. The as-cast device formed using Tol displayed a PCE of 5.4%, higher than that (4.8%) achieved using CF. Combining the effects of thermal annealing and polydimethylsiloxane (PDMS) as a solvent additive, the PCEs of devices prepared using Tol and CF reached 6.20 and 5.52%, respectively. Solvent vapor annealing (SVA), a powerful tool for controlling the morphology of the active layer, had a great impact on the device performance. Tol, tetrahydrofuran (THF), carbon disulphide (CS2), and hexane (Hex) were tested as halogen-free solvents for SVA treatment. Tol- and THF-SVA had positive effects on PCEs, reaching 7.04 and 6.50%, respectively. The enhancement arose mainly from the improvement in the fill factor, due to morphological manipulation and favorable phase separation. CS2- and Hex-SVA treatment had negative effects on the short-circuit current density and, hence, the overall PCE. A PCE of greater than 7% is the highest performance reported to date when using a halogen-free solvent to prepare small-molecule solar cells.

Ternary bulk heterojunctions (BHJs) are platforms that can improve the power conversion efficiencies of organic solar cells. In this paper, we report an all-small-molecule ternary BHJ solar cell incorporating [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) and indene-C60 bisadduct (ICBA) as mixed acceptors and the conjugated small molecule (2Z,2′E)-dioctyl 3,3′-(5′′,5′′′′′-(4,8-bis(5-octylthiophen-2-yl)benzo[1,2-b:5,4-b′]dithiophene-2,6-diyl)bis(3,4′,4′′-trioctyl-[2,2′:5′,2′′-terthiophene]-5′′,5-diyl))bis(2-cyanoacrylate) (BDT6T) as a donor. When incorporating a 15% content of ICBA relative to PC71BM, the ternary BHJ solar cell reached a power conversion efficiency of 6.36% with a short-circuit current density (JSC) of 12.00 mA cm−2, an open-circuit voltage (VOC) of 0.93 V, and a fill factor of 0.57. The enhancement in efficiency, relative to that of the binary system, resulted mainly from the increased value of JSC, attributable to not only the better intermixing of the donor and acceptor that improved charge transfer but also the more suitable morphology for efficient dissociation of excitons and more effective charge extraction. Our results suggest that there is great potential for exceeding the efficiencies of binary solar cells by adding a third component, without sacrificing the simplicity of the fabrication process.

Solution-processed organometal trihalide-based perovskites have attracted attention in the field of solar energy due to their high absorption and low temperature fabrication. We demonstrated the droplet-assisted two-step process of spin coating lead iodide (PbI2) followed by spray coating methylammonium iodide (CH3NH3I) to prepare a continuous lead iodide perovskite film. A simple airbrush gun was used to control the volume of CH3NH3I, in order to attain a uniform, stoichiometric and continuous perovskite film. An insufficient or excess volume of CH3NH3I gives poor crystallinity and morphology, which gradually reduces the device performance. A power conversion efficiency (PCE) of 11.66% was achieved for 100 nm of PbI2 followed by 300 μl of CH3NH3I and annealing at 100 °C for 120 min. To address the reproducibility of the device performance, 50 devices were fabricated for statistical analysis and 80% of the devices showed the average PCE of 10–11% with reproducible JSC, VOC and FF.

A maximal thermoelectric figure-of-merit ZT for p-type Ag(Sb1−xInx)Te2 samples with x = 0.07 is 1.35 at 650 K, yielding an enhancement of greater than 40% compared with that of an undoped AgSbTe2 compound at the same temperature. This ZT enhancement can be primarily attributed to both the greatly enhanced power factor resulting from an increase in Seebeck coefficient because of the increase in the effective mass and the substantial decrease in thermal conductivity which could be ascribed to the enhancement of the phonon scattering mechanism by dopants with different atomic weights. These results indicate that doping with In is effective for enhancing the thermoelectric performance of the p-type AgSbTe2 compound.

In this study we used convergent syntheses to prepare two novel acceptor–donor–acceptor (A–D–A) small molecules (BT4OT, BT6OT), each containing an electron-rich benzotrithiophene (BT) unit as the core, flanked by octylthiophene units, and end-capped with electron-deficient cyanoacetate units. The number of octylthiophene units affected the optical, electrochemical, morphological, and photovoltaic properties of BT4OT and BT6OT. Moreover, BT4OT and BT6OT possess low-energy highest occupied molecular orbitals (HOMOs), providing them with good air stability and their bulk heterojunction (BHJ) photovoltaic devices with high open-circuit voltages (Voc). A solar cell device containing BT6OT and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) in a 1:0.75 ratio (w/w) exhibited a power conversion efficiency (PCE) of 3.61% with a short-circuit current density (Jsc) of 7.39 mA cm−2, a value of Voc of 0.88 V, and a fill factor (FF) of 56.9%. After adding 0.25 vol% of 1-chloronaphthalene (CN) as a processing additive during the formation of the blend film of BT6OT:PC71BM (1:0.75, w/w), the PCE increased significantly to 5.05% with values of Jsc of 9.94 mA cm−2, Voc of 0.86 V, and FF of 59.1% as a result of suppressed nanophase molecular aggregation.

We systematically investigated the effect of the molecular weight of additives on the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by using different concentrations and molecular weights of polyethylene glycol (PEG) and ethylene glycol (EG). The conductivity enhancement depends on both the molecular weight and concentration of PEG used. The conductivity of PEDOT:PSS was enhanced from 0.3 S cm−1 to 805 S cm−1 with 2% PEG but to only 640 S cm−1 with 6% EG. PEGs with molecular weight higher than 400 have too low mobility to impart the required screening effect, and hence, the conductivity enhancement is less. Through FTIR, XPS and AFM investigations, the mechanism for the conductivity enhancement is found to be charge screening between PEDOT and PSS followed by phase separation and reorientation of PEDOT chains leading to bigger and better connected particles. The molecular weight and concentration of PEG also affect solar cell performances even though the conductivities are the same. Due to their high conductivity and high transmittance, ITO-free organic solar cell devices fabricated using PEDOT:PSS treated with 2% PEG anodes exhibited performance almost equal to that of the ITO counterparts.