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We suggest phase transition-induced surface passivation of alkylammonium formates for effective defect passivation of perovskite, achieving significantly improved efficiency and thermal stability.

Three new cationic cyclometalated iridium(III) complexes equipped with differently substituted benzo[

Ammonia (NH3) has received much attention as a hydrogen carrier because it can be easily liquefied with a high hydrogen storage density and emits no greenhouse gas during the dihydrogen evolution process. The ammonia oxidation reaction (AOR) in an electrochemical system has an important merit in which a very high-purity dihydrogen gas can be obtained without an additional separation process that is typically needed for thermochemical decomposition processes. Herein, the electrochemical AOR was carried out in a solid acid electrolysis cell (SAEC) at an intermediate temperature around 250 °C, in which a solid composite of CsH2PO4 mixed with SiP2O7 was used as an electrolyte and Pt/C-based electrocatalysts were employed as the electrode materials of both anode and cathode. The Pt/C electrode material was modified with the CsH2PO4/SiP2O7 electrolyte in order to enhance the electrocatalytic activity for the AOR with an improved H2 production rate. Over the SAEC system reported here, a high AOR performance was obtained with a current density of 67.1 mA/cm2 and Faradaic efficiency (FE) of 98.2%. This study can suggest the significant potential of SAEC for the carbon-free H2 production from the selective electrochemical oxidation of NH3.

Anode-supported proton-conducting solid oxide fuel cells (PC-SOFCs) fabricated with two representative proton-conducting oxides, BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) and BaZr0.8Y0.2O3-δ (BZY), were compared to obtain the insight into the electrochemical performances when fueled with syngas at 700°C and the correlation between the anode thickness (0.4, 0.8, and 1.6 mm) and operational stability. We have demonstrated that, in stability tests, the BCZYYb cells exhibited significantly higher maximum power density (MPD) than the BZY cells when operating on H2, 1.22 and 0.48 W/cm2 for the BCZYYb and BZY cells, but the BCZYYb cells degraded more rapidly than the BZY cells when operating on syngas. In addition, decreasing the anode thickness significantly enhanced the stability of BCZYYb cells operating on syngas, a reduction of 81, 76, and 71% in MPD for 1.6, 0.8, and 0.4 mm anode after 30 min. The electrochemical impedance spectra and X-ray diffraction patterns indicated that the rapid degradation of cerate-based cells with syngas could be mainly attributed to the considerable increase in polarization resistance due to the phase decomposition of the electrolyte powder in the anode. Heterogeneous catalysis was performed to study the catalytic reaction of the H2–CO mixture over anode powders prepared with the two proton-conducting oxides (Ni-BCZYYb and Ni-BZY) in a fixed bed reactor, and the CO conversion and selectivity to CO2 and CH4 were determined. For all anode powders, continuous CO2 production was initially observed with CH4 formation, and no significant difference in catalytic activity trends was observed between both anode powders. An increased residence time substantially decreased the normalized CO2 yield, which was associated with the potential secondary reaction of CO2 with H2, CH4, or perovskite oxide. Based on the results of heterogeneous catalysis with both anode powders, the observed cell degradation on both cells during operation with syngas may be primarily attributed to carbon coking due to CO disproportionation; however, more than 4 times rapid degradation of the cerate-based cell when operating with syngas was clearly demonstrated to be attributed to the decomposition of the electrolyte powder in anode by the resulting CO2 from the catalytic reaction of the H2–CO mixture.

Although ionic hydrogels have been developed recently for innovative wearable electronics, they necessitate high humidity to diffuse ions in water, which negatively impacts their performance in harsh conditions (e.g., high temperature and dry environments). In this study, a series of p- and n-type polymeric ionic gels (PIGs) with different ratios of ionic side chains are synthesized to allow only single-type ions to pass through them. The results demonstrate that our stretchable PIGs are transparent, thermally robust up to 125°C, and self-healing. Among the series of PIGs, p- and n-type PIGs with 75% ion moieties (P75 and N75) exhibit the optimum ionic conductivity (4.1×10− 4 and 2.7×10− 4 S cm-1) and ionic Seebeck coefficients (5.84, and − 4.18 mV K-1) under ambient conditions (25°C and RH of 30%), resulting in ZTi values of 1.87×10− 3 and 1.18×10− 3. Accordingly, P(([EMIM+][SPA])0.75-r-MA0.25) (P75) and P(([APTA][TFSI-])0.75-r-MA0.25) (N75) are used to achieve stretchable thermoelectric energy generators (TEGs) with stable operability under ambient conditions (RH of 30%), satisfying all of the requirements. TEGs with five pairs of p/n couples exhibit a thermovoltage of up to ~ 0.8 V.

CsPbI3 perovskite quantum dots (CsPbI3-PQDs) have recently come into focus as a light-harvesting material that can act as a platform through which to combine the material advantages of both perovskites and QDs. However, the low cubic-phase stability of CsPbI3-PQDs in ambient conditions has been recognized as a factor that inhibits device stability. TiO2 nanoparticles are the most regularly used materials as an electron transport layer (ETL) in CsPbI3-PQD photovoltaics; however, we found that TiO2 can facilitate the cubic-phase degradation of CsPbI3-PQDs due to its vigorous photocatalytic activity. To address these issues, we have developed chloride-passivated SnO2 QDs (Cl@SnO2 QDs), which have low photocatalytic activity and few surface traps, to suppress the cubic-phase degradation of CsPbI3-PQDs. Given these advantages, the CsPbI3-PQD solar cells based on Cl@SnO2 ETLs show significantly improved device operational stability (under conditions of 50% relative humidity and 1-sun illumination), compared to those based on TiO2 ETLs. In addition, the Cl@SnO2-based devices showed improved open circuit voltage and photocurrent density, resulting in enhanced power conversion efficiency (PCE) up to 14.5% compared to that of TiO2-based control devices (PCE of 13.8%).

The power conversion efficiency of CsPbI

Defect passivation has become essential in improving efficiency and stability in perovskite solar cells. Here, we report the use of (α-methylguanido)acetic acid, also known as creatine, as a passivation molecule. It is employed both as an additive and as a surface passivation layer of perovskite thin films, given its multiple functional groups, which could address different defect sites, and its size, which could inherently affect the material structure. We prove that the surface passivation is more efficiently working by removing vulnerable defects on the surface. Hole and electron defect densities were reduced, leading to the highest power conversion efficiency of 22.6%. In addition, it can effectively protect the perovskite thin film and improve the operational stabilities in high thermal (85 °C) and humid conditions (50% relative humidity), suggesting a strong stability of the surface passivation layer.

The antisolvent method has been used extensively to induce the growth of high-quality perovskite layers for efficient solar cells. However, uncontrollable nucleation and crystallization increases t...

The fine control over the surface of lead sulfide colloidal quantum dots (PbS CQDs) is increasingly important to achieve enhanced device performance. In particular, the in-gap trap state resulting from the surface hydroxylation of PbS CQDs is considered detrimental to photovoltaic performance. In this study, we developed a method to avoid hydroxyl formation on the PbS CQD surface by using an in situ solution-phase ligand-exchange process. The complete elimination of protic solvents and other hydroxyl sources from the CQD synthesis to device fabrication produced PbS CQD films without undesired hydroxyl ligands with a reduced trap density. In this process, the purification process, which accounts for nearly 60% of the synthesis cost, is completely excluded. The presence of trap states verified through optical analysis and the hydroxylation observed via surface analysis clearly agreed with the device characterization obtained by transient photovoltage and photocurrent. Consequently, the open-circuit voltage of the PbS CQD solar cells is improved by up to 10%, yielding a certified power-conversion efficiency of 11.6%.

To fight against the counteractive triplet–triplet annihilation and vibrational deactivation faced by low bandgap phosphorescent emitters, aggregation-induced phosphorescent enhancement (AIPE)-active deep-red and NIR emissive iridium(III) complexes are designed by suitably anchoring electron-withdrawing substituents such as -phenyl (Ir2), -ethyl ester (Ir3), and -trifluoromethyl (Ir4) groups on the N-coordinating quinoline moiety of a (benzo[b]thiophen-2-yl)quinoline cyclometalated ligand along with ancillary picolinate. The fundamentals of the origin of AIPE on Ir2 and Ir4 and its associated excited-state properties are deeply studied through comparison with unsubstituted Ir1 with the help of density functional theory and single-crystal X-ray diffraction analysis. Most importantly, AIPE-active Ir2 is employed for the development of efficient deep-red and NIR PhOLEDs by hybrid solution-processable methods, in which the AIPE effect of Ir2 reaches a maximum external quantum efficiency (EQE) of 7.29% at high doping ratios.

With the unprecedented development of perovskite solar cells (PSCs), various interlayers have been investigated. Interlayers have diverse roles in shifting the energy levels, attracting and extracting charges, and passivating surface traps. These can improve the stability of PSCs, as well as their power conversion efficiency (PCE). In this study, a small molecular self-assembled monolayer (2-[carbamimidoyl(methyl)amino]acetic acid) is introduced on a SnO2 layer. The acetic acid is known as creatine, existing naturally in the human body. It is eatable and dosed by athletes for energy. Due to its structural properties, creatine can be anchored on a SnO2 layer, thus, it can strengthen the charge extraction from a perovskite layer by forming interface dipoles and reducing the work function. Also, it can passivate the defects in the perovskite layer. These properties are comprehensively investigated via various experimental techniques. With the creatine layer as a cathode interfacial layer on the SnO2 layer, the PSC employing a triple cation-based perovskite achieves the highest PCE of 20.8% and retained 90% of it after 50 days. Furthermore, 22.1% of PCE is obtained from the formamidinium-based perovskite. This report represents an interesting application of creatine as an interlayer in PSCs and suggests the possible application of other essential amino acids.

In recent decades, organic semiconductors (OSCs), which are lightweight, flexible, and have low processing costs, have enabled significant progress in terms of efficiency in the field of organic electronics [e.g., as active materials in organic photovoltaics (OPVs), hole-transporting materials (HTMs) in perovskite solar cells (PSCs), and semiconducting materials in organic thin-film transistors (OTFTs)]. However, most OSCs are currently being processed in halogenated toxic solvents, which creates conditions that are hazardous to the human body and the environment. Accordingly, for large-area fabrication and commercialization, OSCs must be developed to show high solubility in environmentally friendly and non-harmful solvents as well as high performance. This review considers environmentally benign solvents and potential approaches for increasing the solubility of OSCs in relation to Hansen solubility parameters (HSPs) and molecular design. It also provides guidelines regarding molecular design for advanced OSCs possessing additional functions, sustaining green-solvent processability, and superior efficiency. We believe that these efforts toward an environmentally benign process will contribute to the development and commercialization of organic electronics and shed light on future directions for OSC research in relation to industry, the environment, and human life.

Special attention should be devoted to the stability of the perovskite solar cells, which is a major limitation affecting their commercialization. The stabilities against moisture and light have been substantially improved by optimizing the charge-transporting layer and utilizing encapsulation techniques; however, thermal stability has not yet been secured. Herein, we report a novel approach involving metal oxide nanoparticles infiltrated by hole-transporting materials to enhance device stability. Unlike conventional methods that prevent the thermal decomposition of perovskite, we intend to eliminate the main cause of efficiency drop by dissipating the heat accumulated inside the device. In particular, we observe that metal oxide nanoparticles can effectively reduce the device temperatures and maintain the morphology of hole-transporting materials because of their high thermal conductivity and porous scaffold structure. The experiments demonstrate that our devices without encapsulation retained 91% of their initial efficiency after 31 days at 85 °C and 85% relative humidity, which is the condition to simulate a real operating environment. These results show significant potential for the development of highly stable perovskite solar cells with reasonable efficiency.

Defects and energy offsets at the bulk and heterojunction interfaces of perovskite are detrimental to the efficiency and stability of perovskite solar cells (PSCs). Herein, we designed an amphiphilic π-conjugated ionic compound (QAPyBF

Naphthalene diimide (NDI)-based copolymers are promising polymer acceptors in all-polymer solar cells (all-PSCs), but their large crystal domains cause large-scale phase separation in all-polymer blend films. This limits the photovoltaic performance and mechanical stability of all-PSCs. Herein, we control all-polymer blend films by introducing a fluorinated copolymer of NDI and (E)-1,2-bis(3-fluorothiophen-2-yl)ethene (FTVT) (PNDI–FTVT) as a polymer acceptor for flexible all-PSCs. The copolymer PNDI–FTVT has a less crystalline structure and higher electron mobility than its nonfluorinated copolymer counterpart (PNDI–TVT). A blended film incorporating PNDI–FTVT exhibits a well-mixed morphology and improves the chain interconnectivity with a polymer donor, providing better charge transport pathways and enhanced mechanical resilience. The PNDI–FTVT-based flexible all-PSC exhibits enhanced photovoltaic performance in comparison with a PNDI–TVT-based flexible all-PSC (5.11–7.14%) as well as excellent mechanica...

Naphthalene diimide (NDI)-based conjugated polymers with bithiophene or dithienylethene (TVT) units can form large crystal domains through NDI-driven self-assembly and are widely used in organic electronic devices as n-type materials. However, improving electron transport in these semiconducting polymers has been a significant challenge mainly due to poor electrical connections between the crystal domains. Formation of an interconnected network of small domains with short-range ordering and mixed orientations could be an effective way of increasing the electron mobility (μe) of polymeric materials. The present study demonstrates the feasibility of this approach using an NDI-based polymer composed of fluorinated TVT (FTVT) units. The FTVT unit enhances intermolecular interactions between the polymer chains, leading to robust aggregation. This aggregation was found to suppress NDI-driven self-assembly, resulting in interconnected small crystal domains with short-range ordering and good thermal stability at ...

Compounds consisting of the electron-accepting thienoisoindigo (TIIG) moiety with branched alkyl side chains of various lengths were each copolymerized with thiophenylene vinylene thiophene (TVT) and selenophenylene vinylene selenophene (SVS) donor moieties, to investigate how the length of the side chain between the branch point and backbone affects the microstructure and charge transport of thin films made of these TIIGTVT and TIIGSVS copolymers. All of the organic field-effect devices based on these copolymers exhibited p-type behaviors, and these devices displayed hole mobility values as high as 1.15 cm2/V/s. Interestingly, the longer side chains in both series of TIIGTVT and TIIGSVS copolymers, the more improved was the molecular ordering of the thin films. But the relationship between charge mobility and side chain length differed for these two series of copolymers, a result attributed to differences between the microstructures of their films. The TIIGTVT series showed localized aggregation, with the greater length of the side chain between the branch point and backbone enhancing the charge transport by increasing the quantity and average size of the aggregates. In contrast, the TIIGSVS series showed long-range order, and aggregates that were too large and prevented charge transport.

Herein, poly(3-hexylthiophene) films with periodic wavy surface structures are generated upon laser irradiation at a wavelength of 530 nm using a pulse duration of 5 ns and a repetition frequency of 10 Hz. The optical properties of the films irradiated with 1200, 3000, and 6000 pulses, respectively, are studied using various techniques.

Understanding initial electron distribution, diffusion, trapping and extraction processes for charge transfer kinetics in metal halide perovskite thin films is crucial for the improvement in device performances, but it still remains ambiguous in the research community. In particular, the kinetics of early-time carrier trapping should be considered with that of diffusion because these processes competitively occur in the same time domain. We herein presented the role of free electron trapping for the diffusion process by employing a dynamic trapping model on time-resolved photoluminescence, the most commonly employed technique to investigate charge transfer kinetics. The origin of the stretched exponential decay behavior of the trapping process, which appeared in the fast component of TRPL, was phenomenologically described and further clarified through a simulation study. We found that the electron injection coefficient at the interface between the perovskite and the electron transport layer was a more important determinant than the electron mobility of the perovskite in the electron extraction process.

The possibility of future potential applications, spanning from military dark-vision displays and data undergird devices to civilian medical nosology and photobiomodulation light therapy, has created an enormous demand for the development of highly efficient, stable, flexible, and low-cost deep-red emitting luminophores. Herein, two new deep-red (650–800 nm) emissive iridium(III) complexes, Ir1-pic and Ir2-pic, have been developed, based on electron-donating –CH3 substituted and unsubstituted cyclometalating (benzo[b]thiophen-2-yl)quinoline and picolinate ancillary ligands, the structures and distorted octahedral coordination motifs of which were authenticated by single-crystal X-ray diffraction analysis. An in-depth study on the effect of the ancillary ligands on the excited-state process was carried out and the results were compared with reference compounds containing thenoyltrifluoroacetylacetonate in place of the picolinate ancillary ligand. The rigid nature and high triplet energy levels of the picolinate ancillary ligand led to a robust deep-red emission; however, the triplet spin density population and flexible nature of the β-diketonate ancillary ligand triggered an excited-state geometrical deformation, leading to the opening up of dominant, unfavorable, nonradiative pathways. Most importantly, the picolinate coordinated complexes Ir1-pic and Ir2-pic were found to exhibit excellent emission efficiencies (ΦPL = 0.48 and 0.37, respectively) and were effectively employed as deep-red dopants in organic light-emitting diodes, constructed via a solution-processed approach. The unoptimized Ir1-pic and Ir2-pic-based devices with various doping ratios were found to have maximum external quantum efficiency values of 5.03% and 3.41%, respectively.

To improve the photovoltaic performance of fullerene-free organic solar cells (OSCs), the domain size of the polymer blend film is often reduced using low-volatility solvents and additives. However, since the resulting film is thermodynamically unstable, chemical modification of the polymer is necessary to obtain small domain size from low crystallinity. In this study, we synthesized a new random π-conjugated polymer (asy-PBDTPBT) and investigated the effect of its structural irregularity arising from random copolymerization and from introducing an asymmetric third component. The crystallinity of asy-PBDTPBT was remarkably lower than that of the control polymer (PBDTP) owing to its higher degree of irregularity. According to the tendency of this irregularity, non-fullerene OSCs using asy-PBDTPBT (power conversion efficiency (PCE) of 8.22%) outperformed those using PBDTP (7.37%).

Organic photovoltaics (OPVs) are a promising next-generation photovoltaic technology with great potential for wearable and transparent device applications. Over the past decades, remarkable advances in device efficiency close to 20 % have been made for bulk heterojunction (BHJ)-based OPV devices with long-term stability, and room for further improvements still exists. In recent years, ancillary components have been demonstrated as effective in improving the photovoltaic performance of OPVs by controlling the optoelectronic and morphological properties of BHJ blends. Herein, an updated understanding of polymer-based blend OPVs is provided, and the role and impact of ancillary components in various blend systems are categorized and discussed. Lastly, a strategic perspective on the ancillary components of blend-based OPVs for commercialization is provided.

The effects of the microstructure of conjugated polymer thin films on charge trapping and operational stability of organic field-effect transistors (OFETs) are investigated. Device characteristics of OFETs based on two model conjugated polymers, poly(3-hexylthiophene) (P3HT) and a random 3-hexylthiophene-thiophene copolymer (RP33), are compared. P3HT films have high crystallinity and long-range molecular order, whereas RP33 films have low crystallinity and short-range molecular order as well as enhanced polymer backbone planarity. Experimental evidence shows that although the microstructure of the RP33 film provides efficient charge transport pathways, its high degree of structural disorder causes severe shallow trapping of charge carriers, which results in its inferior stability under bias stress. This study demonstrates that low-crystalline conjugated polymers with short-range order can provide a high charge-carrier mobility but at the same time be inappropriate for practical OFETs because of their poor intrinsic operational stability.

The need for optoelectronic and chemical compatibility between the layers in colloidal quantum dot (CQD) photovoltaic devices remains a bottleneck in further increasing performance. Conjugated polymers are promising candidates as new hole-transport layer (HTL) materials in CQD solar cells (CQD-SCs) owing to the highly tunable optoelectronic properties and compatible chemistries. A diketopyrrolopyrrole-based polymer with benzothiadiazole derivatives (PD2FCT-29DPP) as an HTL in these devices is reported. The energy level, molecular orientation, and hole mobility of this HTL are manipulated through molecular engineering. By levering the polymer's optical absorption spectrum complementary to that of the CQD active layer, EQE across the visible and near-infrared regions is maximized. As a result, a PD2FCT-29DPP-based device exhibits a fill factor of 70% and approximately 35% efficiency enhancement compared to a PTB7-based device.