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Alkali-salt and Lewis base are introduced into quasi-2D perovskite to modulate the phase distribution and serve as a passivating agent, respectively.

Ternary polymer solar cells were fabricated by introducing dithienocyclopentacarbazole (DTC) based non-fullerene acceptor DTTC-4ClC9 into PM6:BTP-BO-4Cl host blends, and the champion power conversion efficiency of 18.21% was achieved.

Crosslinkable organic semiconductors in optoelectronic devices have attracted extensive attention due to the outstanding advantages of strong solvent resistance and stable film morphology.

A pH-neutral aqueous anthraquinone-iron flow battery is demonstrated. The self-association of the anthraquinone is realized via noncovalent interactions.

Solvent polishing engineering is adopted to remove the relatively loose defect layer without damaging carrier injection in blue perovskite light-emitting-diodes (PeLEDs). Synchronously, the polishing effects depending on the solvents are discussed in detail. Finally, optimized blue PeLEDs were obtained with a maximum external quantum efficiency of 5.18%, high brightness of 3737 cd m

An anthraquinone derivative is developed to modify the SnO2 interface in organic solar cells via the multi-site coordination effect, yielding outstanding photovoltaic performances and device stability.

The narrow bandgap Pb-Sn hybrid perovskite materials with lower toxicities and adjustable optical bandgaps provide the opportunity to construct high-efficiency perovskite solar cells (PerSCs). To solve the issues of the uncontrollable crystallization rate of Pb-Sn perovskite and easy oxidation of Sn2+, a β-diketone-based additive, N,N,N',N'-tetraphenylmalondiamide (TPMA), is introduced to coordinate with Pb2+ and Sn2+. The introduction of TPMA can improve the morphology of perovskite films and decrease the density of defect states, resulting in an enhanced power conversion efficiency of >20% and improved stability. The PerSC without encapsulation retains 94% of its initial efficiency after being stored for 1000 h in a nitrogen-filled glovebox and shows a lifetime of only 8% degradation after being continuously heated for 100 h at 80 °C. This work represents a new strategy of introducing a β-diketone ligand as an additive in precursor engineering for achieving efficient and stable PerSCs.

Organic photovoltaics (OPVs) suitable for application in indoor lighting environments can power a wide range of internet of things (IoT) related electronic devices. The ternary structure has huge advantages in improving the photovoltaic performance of OPVs, including broadening the light absorption, improving the charge transport, manipulating the energy loss (Eloss) and so on. Herein, we use wide-bandgap photo-active materials, including the benzotriazole-based polymer donor (J52-F), chlorinated polymer donor (PM7) and A2-A1-D-A1-A2-structured acceptor (BTA3), to construct ternary OPVs for indoor light applications. Benefitting from the introduction of PM7 as the third component in J52-F:BTA3-based blend, a gratifying PCE of 20.04% with a high VOC of 1.00 V can be obtained under the test conditions with an illumination of 300 lx from an LED lighting source with a color temperature of 3000 K. The excellent device performance is inseparable from the matched spectrum, enhanced light absorption and the reduced Eloss, while the improved charge transport capability and suppression of carrier recombination also play an indelible role. Our work shows a potential material system to meet the requirement of devices applied under indoor light. Moreover, these findings demonstrate that designing multi-component OPVs is indeed a feasible way to further improve the performances of the photovoltaic energy conversion system for indoor applications.

Crystal growth of two-dimensional organic–inorganic hybrid perovskite has attracted much attention toward adjusting the orientation to obtain higher PCE and more lasting operational stability.

An electron collection layer (ECL) between a photoactive overlay and an electrode plays a crucial role in optimizing the light field and charge extraction in bulk-heterojunction (BHJ) polymer solar...

With advances in material science and a more in-depth understanding of device engineering, the power conversion efficiency (PCE) of solution-processed organic photovoltaic (OPV) cells have significantly boosted in the past few years. In 2019, a high PCE of 15.7% was achieved in the OPV cells adopting a wide bandgap polymer PM6 and a new emerging non-fullerene acceptor Y6. Such outstanding performance has attracted lots of research attention, driving considerable efforts to improve or take advantage of the high-performance PM6:Y6-based system. In this review, we first concentrate on the structural characteristics of PM6 and Y6 with the focus on understanding why their combination for OPV application can obtain such high efficiency. We also update the recent progress in highly efficient PM6:Y6-based OPV cells via various optimizing strategies. Then we summarize the other applications of the PM6:Y6-based system in semi-transparent, flexible or laye-by-layer devices. The prospects for future OPV studies will be suggested in the end.

The typical thickness of the photoactive layer in organic solar cells (OSCs) is around 100 nm, which limits the absorption efficiency of the incident light and the power conversion efficiency (PCE) of OSCs. Therefore, light-trapping schemes to reduce the optical losses in the thin photoactive layers are critically important for efficient OSCs. Herein, light-trapping and electron-collection dual-functional small organic molecules, N,N,N',N'-tetraphenyloxalamide (TPEA) and N,N,N',N'-tetraphenylmalonamide (TPMA), are designed and synthesized by a one-step acylation reaction. Driven by strong intermolecular force, TPEA and TPMA tend to self-aggregate into hemispherical light-trapping nanodots on the photoactive layer, resulting in enhanced light harvesting. Meanwhile, TPEA and TPMA demonstrate high electron mobility and excellent electron-collection ability. Compared with the device without cathode buffer layer (CBL, PCE = 14.09%), PM6:BTP-eC9 based OSCs with TPEA and TPMA light-trapping CBLs demonstrate greatly enhanced PCE of 16.21% and 17.85%, respectively. Furthermore, a record PCE of 19.02% can be achieved for PM6:BTP-eC9:PC

Bismuth triiodide (BiI

All-inorganic CsPbI

The integrated perovskite/organic solar cell (IPOSC) is widely concerned as an effective approach to broaden the spectrum of perovskite solar cell (PerSC) by utilizing near-infrared light of lower bandgap organic semiconductor. Compared to tandem solar cells, the IPOSCs eliminate the preparation of the intermediate layer and simplify the manufacturing process, but retain the advantages of wide light harvesting. Meanwhile, the IPOSCs can maintain the open-circuit voltage as high as PerSCs. This review summarizes the recent developments of perovskite materials and low-bandgap organic conjugated materials applied in solar cells. Then, the working mechanism of IPOSCs and the recent developments of IPOSCs based on low-bandgap donor and acceptor materials are highlighted. Besides, the study of charge dynamic in IPOSC is summarized. Finally, the potential of IPOSCs and approach to improve device performance are also envisaged.

Metal halide perovskite light-emitting diodes (PeLEDs) are a new type of electroluminescent device with wide application in flat-panel displays and solid-state lighting. The charge recombination at the electrode interfaces and within the emission layer are the key factors restricting the performance of PeLEDs. In this work, the charge transport layers on both sides of the perovskite are optimized simultaneously to reduce the energy loss at the interfaces. Solution-processed aluminum-doped zinc oxide (AZO) nanoparticles are introduced as the electron transport layer in the traditional device structure, which effectively simplifies the device manufacturing process and greatly improves the device performance. Furthermore, an ultra-thin polymethyl methacrylate (PMMA) layer is introduced as a tunneling layer to reduce the exciton quenching between the hole transport layer and the perovskite emission layer. Poly(2-ethyl-2-oxazoline) (PEOX) is used as an additive to significantly enhance the solvent resistance of the perovskite layer. By collaborative optimization, a deep red PeLED emitting at 683 nm with a turn-on voltage of only 1.6 V and a maximum brightness of 7798 cd m−2 is achieved, providing a new idea for the development of high-performance all-solution-processed PeLEDs.

Carbon dot (CD)-based room temperature phosphorescence (RTP) nanomaterials have constituted a research hotspot in multidisciplinary fields. Among the promising RTP CDs, fluorescence–phosphorescence dual emissive CDs (FP-CDs) are currently drawing enormous attention. Herein, highly efficient blue-green FP-CDs were easily prepared by a solvent-free pyrolysis treatment of hydroxyurea. The obtained FP-CDs showed high photoluminescence and phosphorescence quantum yields of 21% and 13%, respectively. Detailed experimental characterization revealed that the efficient dual-emission property is derived from the aromatic carbonyl groups at the edge of FP-CDs. Benefiting from the unique optical performance, FP-CDs exhibited good potential in anticounterfeiting and information encryption. This study offers a new strategy for developing dual-emission fluorescence–phosphorescence nanomaterials.

Combining wide bandgap and narrow bandgap organic materials to construct tandem organic solar cells (OSCs) offers opportunities for overcoming the efficiency limitation of single-junction OSCs. Com...

Facile synthesis of an interfacial layer in organic solar cells (OSCs) is important for broadening material designs and upscaling photovoltaic conversion efficiency (PCE). Herein, a mild solution process of spin-coating In(acac)3 and Ga(acac)3 isopropanol precursors followed by low-temperature thermal treatment was developed to fabricate In2O3 and Ga2O3 cathode buffer layers (CBLs). The introduction of In2O3 or Ga2O3 CBLs endows PM6:Y6-based OSCs with outstanding performance and high PCEs of 16.17% and 16.01%, respectively. Comparison studies present that the In2O3 layer possesses a work function (WF) of 4.58 eV, which is more favorable for the formation of ohmic contact compared with the Ga2O3 layer with a WF of 5.06 eV and leads to a higher open circuit voltage for the former devices. Electrochemical impedance spectroscopy was performed to reveal how In2O3 and Ga2O3 affect the internal charge transfer and the origin of their performance difference. Although In2O3 possesses lower series resistance loss, Ga2O3 has a higher recombination resistance, which enhances the device fill factor and compensates for its series resistance loss to some extent. Comparative analysis of the photo-physics of In2O3 and Ga2O3 suggests that both are excellent CBLs for highly efficient OSCs.

All-inorganic halide perovskite solar cells (PerSCs) have achieved rapid development in recent years. However, limited by narrow absorption bands, the power conversion efficiency (PCE) of all-inorganic halide PerSCs lag behind the organic-inorganic hybrid ones. In this contribution, to expand their absorption spectra and enhance the PCE, tandem solar cells (TSCs) with inorganic perovskite and organic conjugated molecules are constructed, utilizing CsPbI2Br as an ultraviolet-visible light absorber and a PTB7-Th:IEICO-4F bulk-heterojunction (BHJ) active layer as a near-infrared light absorber. To physically and electronically connect the front and rear subcells, P3HT/MoO3/Ag/PFN-Br is introduced as an interconnecting junction. Finally, the TSCs exhibit a remarkably higher PCE of 17.24% compared to that of the single junction PerSCs (12.09%) and organic solar cells (OSCs) (10.89%). These results indicate that the combination of all-inorganic perovskite and a low bandgap organic active layer for TSCs is a feasible approach to realize broad spectra utilization and efficiency enhancement.

The printable electrode interlayer with excellent thickness tolerance is crucial for mass production of organic solar cells (OSCs) by solution-based print techniques. Herein, high-quality printable SnO2 films are simply fabricated by spin-coating or blade-coating the chemical precipitated SnO2 colloid precursor with post thermal annealing treatment. The SnO2 films possess outstanding optical and electrical properties, especially extreme thickness-insensitivity. The interfacial electron trap density of SnO2 cathode interlayers (CILs) are very low and show negligible increase as the thicknesses increase from 10 to 160 nm, resulting in slight change of the power conversion efficiencies (PCEs) of the PM6:Y6 based OSCs from 16.10% to 13.07%. For blade-coated SnO2 CIL, the PCE remains high up to 12.08% even the thickness of SnO2 CIL is high up to 530 nm. More strikingly, the large-area OSCs of 100 mm2 with printed SnO2 CILs obtain a high efficiency of 12.74%. To the best of our knowledge, this work presents the first example for the high-performance and large-area OSCs with the thickness-insensitive SnO2 CIL.

The organic-inorganic halide perovskite solar cell (PerSC) is the state-of-the-art emerging photovoltaic technology. However, the environmental water/moisture and temperature-induced intrinsic degradation and phase transition of perovskite greatly retard the commercialization process. Herein, a dual-functional organic ligand, 4,7-bis((4-vinylbenzyl)oxy)-1,10-phenanthroline (namely, C1), with crosslinkable styrene side-chains and chelatable phenanthroline backbone, synthesized via a cost-effective Williamson reaction, is introduced for collaborative electrode interface and perovskite grain boundaries (GBs) engineering. C1 can chemically chelate with Sn

The interfaces between the absorber and charge transport layers are shown to be critical for the performance of perovskite solar cells (PSCs). PSCs based on the Spiro-OMeTAD hole transport layers generally suffer from the problems of stability and reproducibility. Inorganic hole transport materials CuCrO

The development of new electron transporting layer (ETL) materials to improve the charge carrier extraction and collection ability between cathode and the active layer has been demonstrated to be an effective approach to enhance the photovoltaic performance of organic solar cells (OSCs). Herein, water-soluble carbon dots (CDs) as ETL material have been creatively synthesized by a vigorous chemical reaction between polyethylenimine (PEI) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) via a simple one-step hydrothermal method. Taking full advantage of the high electron transfer property of PTCDA and the work function (

Power conversion efficiencies (PCEs) and device stability are two key technical factors restricting the commercialization of organic solar cells (OSCs). In the past decades, though the PCEs of OSCs have been significantly enhanced, device instability, especially in the state-of-the-art nonfullerene system, still needs to be solved. In this work, an effective crosslinker (namely, DTODF-4F), with conjugated fluorene-based backbone and crosslinkable epoxy side-chains, has been designed and synthesized, which is introduced to enhance the morphological stabilization of the PM6:Y6-based film. This crosslinker with two epoxy groups can be in situ crosslinked into a stable network structure under ultraviolet radiation. We demonstrate that DTODF-4F, which acted as a third component, can promote the exciton dissociation rate and reduce traps/defects, finally resulting in the enhancement of efficiency. In particular, the OSC devices exhibit better stability under continuous heating owing to the morphology fixation of the bulk heterojunction. This work drives the development direction of morphological stabilization to further improve the performance and stability of OSCs.

Carbon quantum dots (CQDs) have developed into prospective nanomaterials for next-generation lighting and displays due to their intrinsic advantages of high stability, low cost, and environmental friendliness. However, confined by the spin-forbidden nature of triplet state transitions, the highest theoretical value of external quantum efficiency (EQE) of fluorescent CQDs is merely 5%, which fundamentally limits their further application in electroluminescent light-emitting diodes (LEDs). Soluble phosphorescent CQDs offer a means of breaking the shackle to achieve efficient monochromatic electroluminescence, especially red emission, which is a pivotal constituent in full-color displays. Here, the synthesis of red (625 nm) phosphorescent carbon quantum dot organic frameworks (CDOFs) with a quantum yield of up to 42.3% and realization of high-efficiency red phosphorescent electroluminescent LEDs are reported. The LEDs based on the CDOFs exhibited a red emission with a maximum luminance of 1818 cd m-2 and an EQE of 5.6%. This work explores the possibility of a new perspective for developing high-performance CQD-based electroluminescent LEDs.

A series of full-color circularly polarized luminescence (CPL)-active materials are fabricated by judiciously combining multifarious chiral nanoarchitectures with achiral fluorescence dyes. The investigated nanoarchitectures include organic polymer nanofibers, organic-inorganic hybrid nanoflowers, and inorganic nanoflowers. The as-prepared chiral nanoarchitectures all can act as handed-selective fluorescence filters to powerfully transform unpolarized fluorescent light into circularly polarized luminescence. Also notable, no interaction is required between chiral and fluorescent components for achieving CPL emission. The present study provides a convenient and universal approach for preparing full-color CPL materials. Following the strategy, numerous chiroptical materials with CPL performance can be expected due to the abundant chiral matters and achiral fluorophores.

Lead halide perovskites have attracted tremendous attention because of their impressive optoelectronic properties. However, the toxicity of lead remains a bottleneck for further commercial development. Two-dimensional Ruddlesden-Popper tin-based perovskites are lead-free and more stable compared to their three-dimensional counterparts, which have great potential in the optoelectronic device field. Herein, we demonstrate high-quality two-dimensional phenylethylammonium tin-iodide perovskite (PEA2SnI4) thin films by using toluene as the antisolvent. Furthermore, the PeLED performance is greatly improved by replacing the PEAI spacer cation with 2-thiopheneethyllamine iodide (TEAI). As a result, a TEA-based PeLED device is achieved with a low turn-on voltage of 2.3 V, a maximum luminance of 322 cd m-2, and maximum external quantum efficiency of 0.62%, which are the highest efficiency and brightness for pure red (emission peak = 638 nm) tin-based PeLEDs to date.

A bicontinuous interpenetrating donor–acceptor network with a suitable phase-separated domain size is crucial for fabricating highly efficient organic bulk heterojunction solar cells considering the fact that it guarantees effective exciton dissociation and smooth charge transport. For traditional binary blend bulk heterojunctions, the photoactive layer is a simple physical mixture of the donor and acceptor; further, the size of phase separation is primarily determined by the aggregation characteristics of the donor and acceptor. Moreover, it is difficult to control and stabilize it. To resolve this problem, a kind of donor–acceptor integral molecule in which the donor and acceptor units are linked by nonconjugated flexible linking units has been proposed. The energy levels and absorption spectra of the integral molecules can be easily controlled by tuning the donor and acceptor units. Furthermore, these integral molecules can form a microphase-separated bulk heterojunction of the donor and acceptor phases via a self-assembly process of the molecule, which is governed by the flexible linking unit responsible for connecting the donor and acceptor units. Since the donor and acceptor units of the integral molecules are connected by nonconjugated units, the scale of aggregation and morphological stability can be easily controlled. In this review, we first introduce the unique characteristics of three typical donor–acceptor integral molecules and then highlight their current developments. For each donor–acceptor molecule, we attempt to give a detailed summary with regard to their design and synthesis, and an in-depth understanding on the basic mechanism of molecular self-assembly and the performance comparison of SMSCs. In the end, the prospect and potential improvements in the donor–acceptor integral molecule are addressed. We believe that emerging donor–acceptor molecules can provide worthwhile opportunities for the fabrication of efficient and stable organic solar cells.

The development of efficient and stable interface materials is an important part of the research in organic photovoltaics (OPVs), which aims to realize higher efficiency, longer lifetime, lower cost, easier fabrication, and wider applicability. MoO3 exhibits a suitable work function, adjustable electronic structure, favorable ohmic contact with organic materials, remarkable stability in the presence of water and oxygen, and excellent solution processing properties, making it an ideal anode buffer layer (ABL) for OPVs. This review analyzes the photoelectric characteristics of MoO3 based on the crystalline structure and its fundamentals as an ABL in OPVs. To simplify the fabrication procedure, AHM, MoO2(acac)2, and MoO3 powder are used as precursors for solution processing MoO3 buffer layers, and the attempts are still ongoing. Strategies of composite/hybrid formation, modification and doping are utilized to optimize the MoO3 ABL to obtain more efficient and stable OPVs. Combining the optical and electronic properties of MoO3, diverse applications are introduced in inverted, semi-transparent devices and tandem architectures, showing the wide applicability of MoO3 in OPVs. This review draws the outline of the relationships between the composition, structure and processing method of MoO3 and device performance, and further studies to fully understand it at a deeper level are highly needed, which is beneficial to improve the performance of OPVs and the research for solar cells with a similar structure, such as perovskite solar cells.

The electrode buffer layer plays a more crucial role in semi-transparent organic solar cells (ST-OSCs) than in opaque devices due to the additional requirements of the average visible transmittance (AVT) and color rendering index (CRI) besides the power conversion efficiency (PCE). Herein, we developed a novel cathode buffer layer aluminum(III) acetylacetonate (Al(acac)3) via mild spin-coating with a post low temperature heat treatment process. Studies show that the Al(acac)3 film possesses outstanding optical features and a suitable energy level. Namely, the absorption of an Al(acac)3 film with a thickness of 10 nm is as low as 1% and the transmittance is high, up to 95%, in the visible and near infrared regions, guaranteeing full absorption of the photoactive layer and a high CRI for ST-OSCs; and the suitable energy level ensures a smooth electron transport and collection process. By introducing the Al(acac)3 film in ST-OSCs, the devices based on PM6:Y6 yield an efficiency of 12.41%, an AVT of 25.33% (from 370 nm to 740 nm) and a CRI of 94.6. Encouragingly, the large-area ST-OSC of 100 mm2 with the Al(acac)3 buffer layer yields an efficiency of 11.28%. Further, the long-term stability of ST-OSCs shows that the device with encapsulation retains 60% of the initial PCE over 60 hours of continuous illumination. The results indicate that Al(acac)3 is a promising cathode buffer layer for fabricating efficient, large area and stable semi-transparent organic solar cells.

A novel crosslinkable acetylacetone chelate, Hf(ACBV)4, was designed and synthesized using 1,3-bis(4-vinylphenyl)propane-1,3-dione (ACBV) and hafnium chloride (HfCl4). The obtained crosslinked chelate film exhibits excellent solvent-resistance property and was successfully applied as the electron transport layer in inverted polymer solar cells (PSCs). The crosslinking property was proved by differential scanning calorimetry (DSC) measurements and the unchanged UV-visible absorption of the crosslinked film after washing with chloroform. The obtained crosslinked Hf(ACBV)4 film can effectively ameliorate the contact between ITO and the photoactive layer, facilitating the charge transfer process of the device. Moreover, the devices based on PM6:Y6 achieved an efficiency of 15.17% and exhibited excellent stability with 90% retention efficiency after 20 h of continuous illumination in air. Our work demonstrates a new approach in designing effective crosslinkable chelates as ETLs to improve the stability and efficiency of PSCs.

Rigid three-dimensional polycyclic aromatic hydrocarbons (3D PAHs) are garnering great interest due to their unique molecular shapes and interesting optoelectronic properties. Herein we report the synthesis of two 3D PAHs with perylene monoimide (PMI) and naphthalene subunits fused on [3,3,3]propellanes. The resulting compounds (P-1 and P-2) are unambiguously characterized by spectral analysis and theoretical calculations. It is found that the subunits can significantly influence the electronic properties and electron communications in 3D PAHs. In contrast to the naphthalene subunit, the PMI subunit leads to the enhancement of electron communication in 3D PAHs and amplifies the absorption coefficients when compared to the individual PMI subunit. In addition, UV-vis measurement suggests the presence of homoconjugation between the subunits. These compounds exhibit p-type behaviors with the mobilities on the order of 10−5 to 10−4 cm2 V−1 s−1. Additionally, these 3D PAHs show strong fluorescence and are employed as emitters for organic light-emitting diodes.

Sustainable, environment-friendly phosphors produced from cheap and readily available precursor materials using green preparation processes are in high demand for lighting applications. Herein, a composite phosphor comprising carbon dots (CDs) and graphitic carbon nitride (g-C3N4) is prepared on a large scale from citric acid and urea in water, through a green microwave assisted in situ heating method. An optimized CDs@g-C3N4 composite with a 1 wt% loading of CDs shows a strong green emission under 410 nm excitation, with a photoluminescence quantum yield of 62% in the solid state. Using this composite as a phosphor in the color conversion layer, a white light emitting diode with a power efficiency of up to 42 lm W−1 is fabricated.