Search

Seeking clean energy as an alternative to traditional fossil fuels is the inevitable choice to realize the sustainable development of the society. Photocatalytic technique is considered a promising energy conversion approach to store the abundant solar energy into other wieldy energy carriers like chemical energy. Carbon dots, as a class of fascinating carbon nanomaterials, have already become the hotspots in numerous photoelectric researching fields and particularly drawn keen interests as metal‐free photocatalysts owing to strong UV–vis optical absorption, tunable energy‐level configuration, superior charge transfer ability, excellent physicochemical stability, facile fabrication, low toxicity, and high solubility. In this review, the classification, microstructures, general synthetic methods, optical and photoelectrical properties of carbon dots are systematically summarized. In addition, recent advances of carbon dots based photoinduced reactions including photodegradation, photocatalytic hydrogen generation, CO2 conversion, N2 fixation, and photochemical synthesis are highlighted in detail, deep insights into the roles of carbon dots in various systems combining with the photocatalytic mechanisms are provided. Finally, several critical issues remaining in photocatalysis field are also proposed. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystal (PNC) solar cells have attracted increasing interest in recent years because of their excellent optoelectronic properties and unique advantages, which distinguish them from conventional nanocrystals and their bulk counterparts. This emerging type of photovoltaic is promising but faces many challenges regarding commercialization. Therefore, a comprehensive review is presented on the recent progress and current challenges in PNC solar cells. It begins by reviewing the optoelectronic, unique properties of PNCs for photovoltaic devices. Then, the limiting factors on performance are detailed and analyzed with respect to the Shockley–Queisser limit, followed by a summary of effective strategies for efficiency improvement alongside other promising ideas. Finally, the present challenges are discussed toward high‐efficiency, stable, easy‐to‐process, and low‐cost, commercial, PNC photovoltaics. This review aims to attract further attention to the design and development of PNC solar cells, which will accelerate their progress. [ABSTRACT FROM AUTHOR]

CsPbX3 (X = Cl, Br, I) inorganic perovskite nanocrystals (PNCs) not only maintain the excellent optical and electronic properties of bulk material but also possess the features of nano‐materials, such as tunable bandgap and easily processable colloidal ink, and enable them to be suitable for incorporation into various electronic devices and compatible with printing techniques. In contrast to the traditional II‐VI and III‐V semiconductor nanocrystals, the unique defect‐tolerance effect makes the CsPbX3 PNCs promising materials for optoelectronic applications. The ligands around the PNCs play a critical role in the optoelectronic devices performance. Herein, through a facile hexane/ethyl acetate (MeOAc) solvent treatment method to control the ligand amount around CsPbBrI2 PNCs, the impact of ligand amount on the performance of solar cell is systematically demonstrated and the ligand amount is quantified precisely via the nuclear magnetic resonance internal standard method. Through controlling the ligand amount, the film quality, charge transfer, and transport properties are largely improved. In addition, a simple annealing process is applied to improve the interface properties by partial crystal fusion. As a consequence, the photovoltaic power conversion efficiency of 12.2% is achieved, which is the highest performance reported for mixed‐halide CsPbX3 PNCs solar cells. [ABSTRACT FROM AUTHOR]

Controlling the transport and minimizing charge carrier trapping at interfaces is crucial for the performance of various optoelectronic devices. Here, how electronic properties of stable, abundant, and easy‐to‐synthesized carbon dots (CDs) are controlled via the surface chemistry through a chosen ratio of their precursors citric acid and ethylenediamine are demonstrated. This allows to adjust the work function of indium tin oxide (ITO) films over the broad range of 1.57 eV, through deposition of thin CD layers. CD modifiers with abundant amine groups reduce the ITO work function from 4.64 to 3.42 eV, while those with abundant carboxyl groups increase it to 4.99 eV. Using CDs to modify interfaces between metal oxide (SnO2 and ZnO) films and active layers of solar cells and light‐emitting diodes (LEDs) allows to significantly improve their performance. Power conversion efficiency of CH3NH3PbI3 perovskite solar cells increases from 17.3% to 19.5%; the external quantum efficiency of CsPbI3 perovskite quantum dot LEDs increases from 4.8% to 10.3%; and that of CdSe/ZnS quantum dot LEDs increases from 8.1% to 21.9%. As CD films are easily fabricated in air by solution processing, the approach paves the way to a simplified manufacturing of large‐area and low‐cost optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: Hydrothermal/solvothermal treatments have been widely used to prepare carbonized polymer dots (CPDs) through the condensation and carbonization of small molecules and/or polymers. However, the basic scientific issues, such as the nucleation and growth process, morphology and size control, yield increase, and photoluminescence (PL) mechanism have not been well investigated. In this work, enlightened by the principle of soap‐free emulsion polymerization, CPDs with ultrahigh yields (ca. 85 %) were obtained by hydrothermal addition polymerization and carbonization (HAPC) of monomers. The unprecedented initiator‐induced addition polymerization was exploited to synthesize CPDs for the first time. As expected in typical emulsion polymerization processes, the developed HAPC method can produce CPDs with designed sizes by systematically regulating the HAPC parameter, uncovering an unprecedented strategy for regulating the size of CPDs. In addition, the obtained CPDs were provided with high photoluminescence quantum yields (PLQY) up to 45.58 %, while the relationship between the photoluminescence (PL) mechanism and chemical structure was investigated. The viscosity parameter was first adopted to measure the polymer property of CPDs. Moreover, the ultrahigh yield and low‐cost CPDs elicited the high‐performance CPDs/PVA nanocomposite (PVA=poly(vinyl alcohol)) with fluorescence and room‐temperature phosphorescence dual‐mode emission, demonstrating potential for advanced anti‐counterfeit applications. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the ability of tuning work function for polymer carbon dots (PCDs) is systematically studied for the first time. Their application of both cathode and anode interlayers in polymer solar cells (PSCs) is achieved. PCDs possess abundant surface functional groups, which can be modified under control. Through regulating surface groups with more electron‐donating amino (PCD‐NH2) or electron‐withdrawing carboxy (PCD‐COOH), PCDs can decrease or increase work function of electrode, respectively. Therefore, PCD‐NH2 can act as cathode interlayer while PCD‐COOH plays the role of anode interlayer in PSCs. The single material system to act as both interlayers is rarely reported previously. This can simplify the design of materials and the device fabrication process. In addition, PCDs are green, low‐cost, stable, and easily fabricated. Therefore, it is demonstrated that PCDs are promising for commercial interlayer materials in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous‐solution‐processed solar cells (ASCs) are promising candidates of the next‐generation large‐area, low‐cost, and flexible photovoltaic conversion equipment because of their unique environmental friendly property. Aqueous‐solution‐processed polymer/nanocrystals (NCs) hybrid solar cells (AHSCs) can effectively integrate the advantages of the polymer (e.g., flexibility and lightweight) and the inorganic NCs (e.g., high mobility and broad absorption), and therefore be considered as an ideal system to further improve the performance of ASCs. In this work, double‐side bulk heterojunction (BHJ), in which one BHJ combines the active material with electron transport material and the other combines the active material with hole transport material, is developed in the AHSCs. Through comparing with the single‐side BHJ device, promoted carrier extraction, enhanced internal quantum efficiency, extended width of the depletion region, and prolonged carrier lifetime are achieved in double‐side BHJ devices. As a result, power conversion efficiency exceeding 6% is obtained, which breaks the bottleneck efficiency around ≈5.5%. This work demonstrates a device architecture which is more remarkable compared with the traditional only donor–acceptor blended BHJ. Under conservative estimation, it provides instructive architecture not only in the ASCs, but also in the organic solar cells (SCs), quantum dot SCs, and perovskite SCs. [ABSTRACT FROM AUTHOR]

Recently, photovoltaic devices based on aqueous materials are drawing more and more attentions following the green chemistry concept. This review aims to present a general overview of polymer-nanocrystal hybrid photovoltaic devices based on aqueous materials. First, all-organic polymer solar cells based on water-soluble polymers as the active layer are briefly introduced. After that, we focus on the recent development of hybrid solar cells from aqueous polymers and colloidal nanocrystals. Finally, the remaining part of this review is focused on the challenges and proposed solutions associated with the aqueous-solution-processed hybrid solar cells. [ABSTRACT FROM AUTHOR]

Nanoscale CdTe‐CdS bulk heterojunctions are constructed in situ by annealing mercaptoethylamine‐stabilized CdTe nanocrystals (NCs), which exhibit efficient separation, transport, and injection of photogenerated carriers. Inorganic NC solar cells based on the CdTe‐CdS bulk heterojunction exhibit a power conversion efficiency of up to 4% and an internal quantum efficiency approaching 100%. [ABSTRACT FROM AUTHOR]

A solution‐processed gold nanoparticle (NP) top electrode is investigated for large‐area solar cells. The large‐area gold NP film is obtained using a dip‐coating technique. The gold NP film shows an extremely low electric resistance of 2 Ω/◻. All‐solution‐processed solar cells are also fabricated with an optimized power conversion efficiency of 1.71% [ABSTRACT FROM AUTHOR]

Though the cesium‐based inorganic perovskite solar cells (IPSCs) have developed rapidly in recent two years, the power conversion efficiency (PCE) is still far away from the Shockley–Queisser limit due to the large open‐circuit voltage (Voc) deficit, which results from the large energy loss (Eloss). Large Eloss has been a major obstacle for further efficiency improvement of IPSCs. In this review, the authors, for the first time, focus on investigating the Eloss of IPSCs and start from discussing the essence and origin of the Eloss. Then, the reported efficient methods for reducing the band tails and energy disorder are systematically summarized and reviewed, including crystallization optimization, defect passivation, and interface engineering. Finally, the authors offer an overall perspective on managing Eloss in IPSCs and point out the possible ways to reduce the Eloss and promote the efficiency. This review provides a basic understanding of Eloss and may inspire new designs or more impactful methods for further minimizing the Eloss of IPSCs. [ABSTRACT FROM AUTHOR]

Cesium‐based all‐inorganic perovskite solar cells (PSCs), especially for CsPbI2Br component‐based devices, have attracted increasing attention due to its advantage of superior thermal and phase stability. Since the pioneering study reported in 2016, more than 30 papers have been published, reporting the rapid boost in the power conversion efficiency (PCE) of PSCs to 14.81%. The CsPbI2Br PSC is one of the most remarkable research hotspots in the field of perovskite photovoltaics. In this progress report, the recent advances in CsPbI2Br PSCs are systematically reviewed, which in turn introduces the basic property and stability of active layers, and the performance improvements in these devices. The challenges as well as the possible solutions toward better‐performing CsPbI2Br PSCs are also discussed. The theoretical calculation results point out that there is much room for further device performance enhancement, particularly in open‐circuit voltages. This progress report focuses on CsPbI2Br material properties and summarizes recent strategies to improve the corresponding device's PCE, in order to open new perspectives toward commercial utility of PSCs. The theoretical power conversion efficiency of all‐inorganic CsPbI2Br perovskite solar cells is predicted to be 22.1%, and only by taking both material chemistry and device physics into consideration can researchers achieve this goal. [ABSTRACT FROM AUTHOR]