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White‐light‐emitting carbon dots (WCDs) show innate advantages as phosphors in white light‐emitting diodes (WLEDs). For WLEDs, the color rendering index (CRI) is the most important metric to evaluate its performance. Herein, WCDs are prepared by a facile one‐step solvothermal reaction of trimellitic acid and o‐phenylenediamine. It consists of four CDs identified by column chromatography as blue, green, yellow, red, and thus white light is a superposition of these four types of light. The mixture of the four CDs undergoes Förster resonance energy transfer to induce the generation of white light. The photoluminescence of WCDs originates from the synergistic effect of carbon core and surface states. Thereinto, the carbon core states dominate in RCDs, and the increase of amide contents and degree of conjugation promote the redshift of the emission spectra, which is further confirmed by theoretical calculations. In addition, a high CRI of 97 is achieved when the WCDs are used as phosphors to fabricate WLEDs, which is almost the highest value up to now. The multicolor LEDs can also be fabricated by using the four multicolor CDs as phosphors, respectively. This work provides a novel approach to explore the rapid preparation of low‐cost, high‐performance WCDs and CDs‐based WLEDs. The white‐light‐emitting carbon dots are synthesized by a one‐step solvothermal method of trimellitic acid and o‐phenylenediamine, which consists of four types of carbon dots emitting blue, green, yellow, and red light. Five kinds of light‐emitting diodes can be prepared using the above carbon dots, among which the color rendering index of white light‐emitting diode is as high as 97.

Organic solar cells (OSCs) have gained a rapid development in the past two decades and the power conversion efficiency (PCE) of single-junction OSC has recently approached 20%. The novel materials and device engineering are two key factors of this evolution. In this review, the device engineering, including morphology characterization and optimization, device physics, flexible and large-area OSCs, and stability of OSCs are systematically summarized. In addition, the current challenges, problems and future developments are also discussed.

Flexible large-area monolithic organic solar cells suffer from electrical loss during up-scaling due to the limited conductivity of transparent electrodes. In this work, highly conductive silver grid fingers are integrated onto a roll-to-roll gravure-printed silver nanowire electrode via roll-to-roll screen printing, significantly reducing the composite sheet resistance from 15 to 1.5 Ω sq . A numerical model is established to optimize grid width and spacing, achieving an equivalent sheet resistance of 1 ~ 2 Ω sq for higher-resistance electrodes. A self-masking strategy is developed to prevent shunting caused by uneven grid surfaces. As a result, monolithic flexible organic solar cells with areas of 4 and 16 cm² achieve power conversion efficiencies of 15.20% and 14.24%, respectively, demonstrating minimal efficiency loss with increased area. Additionally, the devices exhibit excellent mechanical flexibility and shelf stability, enabled by a robust photoresist passivation layer.

Improving thermal stability is of great importance for the industrialization of polymer solar cells (PSC). In this paper, we systematically investigated the high-temperature thermal annealing effect on the device performance of the state-of-the-art polymer:non-fullerene (PM6:Y6) solar cells with an inverted structure. Results revealed that the overall performance decay (19% decrease) was mainly due to the fast open-circuit voltage (VOC, 10% decrease) and fill factor (FF, 10% decrease) decays whereas short circuit current (JSC) was relatively stable upon annealing at 150 °C (0.5% decrease). Pre-annealing on the ZnO/PM6:Y6 at 150 °C before the completion of cell fabrication resulted in a 1.7% performance decrease, while annealing on the ZnO/PM6:Y6/MoO3 films led to a 10.5% performance decay, indicating that the degradation at the PM6:Y6/MoO3 interface is the main reason for the overall performance decay. The increased ideality factor and reduced built-in potential confirmed by dark J − V curve analysis further confirmed the increased interfacial charge recombination after thermal annealing. The interaction of PM6:Y6 and MoO3 was proved by UV-Vis absorption and XPS measurements. Such deep chemical doping of PM6:Y6 led to unfavorable band alignment at the interface, which led to increased surface charge recombination and reduced built-in potential of the cells after thermal annealing. Inserting a thin C60 layer between the PM6:Y6 and MoO3 significantly improved the cells’ thermal stability, and less than 2% decay was measured for the optimized cell with 3 nm C60.

Despite the tremendous efforts in developing non‐fullerene acceptor (NFA) for polymer solar cells (PSCs), only few researches are done on studying the NFA molecular structure dependent stability of PSCs, and long‐term stable PSCs are only reported for the cells with low efficiency. Herein, the authors compare the stability of inverted PM6:NFA solar cells using ITIC, IT‐4F, Y6, and N3 as the NFA, and a decay rate order of IT‐4F > Y6 ≈ N3 > ITIC is measured. Quantum chemical calculations reveal that fluorine substitution weakens the C═C bond and enhances the interaction between NFA and ZnO, whereas the β‐alkyl chains on the thiophene unit next to the C═C linker blocks the attacking of hydroxyl radicals onto the C═C bonds. Knowing this, the authors choose a bulky alkyl side chain containing molecule (named L8‐BO) as the acceptor, which shows slower photo bleaching and performance decay rates. A combination of ZnO surface passivation with phenylethanethiol (PET) yields a high efficiency of 17% and an estimated long T80 and Ts80 of 5140 and 6170 h, respectively. The results indicate functionalization of the β‐position of the thiophene unit is an effective way to improve device stability of the NFA. Fluorine substitution increases the interaction with ZnO and accelerates the photon decomposition of A‐D‐A type (nonfullerene acceptor) NFA, while he β‐alkyl chains on the thiophene unit next to the C═C linker improves the stability of acceptor molecules by forming protecting atomic cage. When using PET‐treated ZnO and L8‐BO as the electron acceptor, T80 was estimated over 5000 h.

With the rapid progress of organic solar cells (OSCs), improvement in the efficiency of large‐area flexible OSCs (>1 cm2) is crucial for real applications. However, the development of the large‐area flexible OSCs severely lags behind the growth of the small‐area OSCs, with the electrical loss due to the large sheet resistance of the electrode being a main reason. Herein, a high conductive and high transparent Ag/Cu composite grid with sheet resistance <1 Ω sq−1 and an average visible light transparency of 84% is produced as the transparent conducting electrode of flexible OSCs. Based on this Ag/Cu composite grid electrode, a high efficiency of 12.26% for 1 cm2 flexible OSCs is achieved. The performances of large‐area flexible OSCs also reach 7.79% (4 cm2) and 7.35% (9 cm2), respectively, which are much higher than those of the control devices with conventional flexible indium tin oxide electrodes. Surface planarization using highly conductive PEDOT:PSS and modification of the ZnO buffer layer by zirconium acetylacetonate (ZrAcac) are two necessary steps to achieve high performance. The flexible OSCs employing Ag/Cu grid have excellent mechanical bending resistance, maintaining high performance after bending at a radius of 2 mm. High performance flexible organic solar cells with efficiency above 12% for 1 cm2 cells are fabricated using a Ag/Cu composite grid electrode. The excellent optical and electrical properties of the Ag/Cu electrode contribute to the high performance and good mechanical resistance of the flexible organic solar cell.

Benzo[1,2- b :4,5- b ′]dithiophene (BDT) is an excellent building block for constructing π-conjugated molecules for the use in organic solar cells. In this paper, four 4,8-bis(5-alkyl-2-thienyl)benzo[1,2- b :4,5- b ′]dithiophene (TBDT)-containing A–π–D–π–A-type small molecules (COOP- n HT-TBDT, n = 1, 2, 3, 4), having 2-cyano-3-octyloxy-3-oxo-1-propenyl (COOP) as terminal group and regioregular oligo(3-hexylthiophene) (nHT) as the π-conjugated bridge unit were synthesized. The optical and electrochemical properties of these compounds were systematically investigated. All these four compounds displayed broad absorption bands over 350–600 nm. The optical band gap becomes narrower (from 1.94 to 1.82 eV) and the HOMO energy levels increased (from −5.68 to −5.34 eV) with the increase of the length of the π-conjugated bridge. Organic solar cells using the synthesized compounds as the electron donor and PC 61 BM as the electron acceptor were fabricated and tested. Results showed that compounds with longer oligothiophene π-bridges have better power conversion efficiency and higher device stability. The device based on the quaterthiophene-bridged compound 4 gave a highest power conversion efficiency of 5.62% with a V OC of 0.93 V, J SC of 9.60 mA·cm −2 , and a FF of 0.63.

The conductivity of AgNWs electrodes can be enhanced by incorporating Ag grids, thereby facilitating the development of large‐area flexible organic solar cells (FOSCs). Ag grids from vacuum evaporation offer the advantages of simple film formation, adjustable thickness, and unique structure. However, the complex 3D multi‐component structure of AgNWs electrodes will exacerbate the aggregation of large Ag particles, causing the device short circuits. To address this issue, the relationship between the surface energy of modification layers and the morphology and conductivity of ultrathin Ag on AgNWs is studied. The amorphous ZnO (α‐ZnO) layer promotes Ag growth from Volmer–Weber (VW) to Frank–Van der Merwe (FM), reducing particle aggregation. The 1 µm thick PET/AgNWs/Ag grid electrode with α‐ZnO exhibited low contact resistance and high conductivity. As a result, 1 cm2 FOSCs with Ag grids achieve a power conversion efficiency (PCE) of 16.01%. As the area increased to 4 and 9 cm2, the performance of the monolithic FOSCs is 14.70% and 12.69%, showing less efficiency loss during upscaling. The 8 and 16 cm2 modules constructed by series and parallel connection of the monolithic devices yield PCEs of 14.47% and 12.92%, respectively. This study offers valuable insights into constructing Ag grids on AgNWs electrodes for highly efficient large‐area FOSCs. In this work, composite flexible electrodes of AgNWs/Ag grid are developed for large‐area monolithic flexible organic solar cells (FOSCs). The growth of the Ag on the AgNWs electrodes is successfully transferred from Volmer–Weber (VW) to Frank‐Van der Merwe (FM) by modifying the AgNWs with α‐ZnO. With the reduced aggregation of large Ag particles, the electrode performance and device success rate are improved.

To lower the HOMO energy level of polythiophenes, carboxylate groups were introduced to the β-position of the thiophene unit, by which two polythiophenes with tetrathiophene (poly[5,5′′-(bis-3,3′′-((2-butyloctyl)-carboxylate)-2,2′:2′,2′′-terthiophene)- alt -5-thiophene], P-4T-2COOR ) or pentathiophene (poly[5,5′′-(bis-3,3′′-((2-butyloctyl)-carboxylate)-2,2′:2′,2′′-terthiophene)- alt -5,5′-(2,2′-bithiophene)], P-5T-2COOR ) repeating unit were synthesized. Absorption spectroscopy and cyclic voltammetry measurements revealed that the β-carboxylate substitution red-shifts the maximum absorption wavelength ( λ max abs ) in solution owing to the electron accepting nature of the carboxylate group. In addition, the introduction of β-carboxylate reduces the HOMO level from -5.09 eV for P3HT to -5.34 eV and -5.18 eV for P-4T-2COOR and P-5T-2COOR , respectively, which is in good agreement with quantum chemisty calculation results. However, the β-carboxylate side chain showed different orientation to that of P3HT, which leads to weaker intermolecular π-π interaction as confirmed by less red-shited absorption in thin solid film and the quantum calculation results. Polymer solar cells using P-4T-2COOR and P-5T-2COOR as the electron donor, 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐ d :2′,3′‐ d ′]‐s‐indaceno‐[1,2‐ b :5,6- b ′]di‐thiophene (ITIC) as the electron acceptor were fabricated and tested. The P-4T-2COOR and P-5T-2COOR based cells showed high open circuit ( V OC ) of 0.73–0.99 V, significantly higher than that of P3HT based cell ( V OC of 0.52 V), which can be ascribed to the lower HOMO energy levels and less condensed molecular packing of these two polymers.

Artificial synapses have emerged as a pivotal technological advancement in mimicking brain functions. Organic memristors are desirable for hardware implementation of artificial synapses, owing to their remarkable mechanical flexibility, high biocompatibility at cell‐device interfaces, and adjustable material structure. Developing appropriate organic polymers with carbon dots modification will enable the memristor to possess analog‐type resistive switching behavior, crucial for realizing brain‐like associative learning and adapting dynamic variations of neuron connection strength. In this work, an artificial synapse based on the analogue organic memristor integrating neuromorphic computing and neural interface functions is proposed, utilizing synthetic conjugated porous polymers to construct composites with boron‐doped carbon dots. The structure‐property relationship of alkynyl and alkyl chains in polymers is elucidated, alongside the synergistic effect of local photoinduced redox and hole templating in composites that endows the device with analog‐type resistive switching behavior. Moreover, the memristor presents impressive synaptic plasticity and associative memory learning potential for neuromorphic computing, and further serves as a core unit in flexible artificial neural interface chips, demonstrating dynamic information transmission with neural systems. This study will promote the further development of organic artificial synapses for neuromorphic computing and brain‐machine interfaces. The conjugated porous polymers integrated with boron‐doped carbon dots form a composite for organic memristor in an artificial synapse. The memristor shows analog‐type resistive switching behavior under ultraviolet irradiation, which is attributed to photoinduced redox. This artificial synapse exhibits promising potential in neuromorphic computing and neural interface.