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Cesium lead halide perovskite nanocrystals (PNCs) exhibit promising prospects for application in optoelectronic devices. However, electroactivated near-infrared (NIR) PNC light-emitting diodes (LEDs) with emission peaks over 800 nm have not been achieved. Herein, we demonstrate the electroactivated NIR PNC LEDs based on Yb

PCEs of 14.81% and 17.53% are achieved in BHJ and LbL-PSCs with PNTB6-Cl and Y6 as active layers, and DPE and DFB as solvent additives, respectively. The PCE improvement can be confirmed from the optimized crystallinity and morphology of films.

PCEs of 15.81% and 15.29% are achieved in LbL and BHJ all-PSCs with polymer donor PM6, polymer acceptor PY-IT and CN as an additive. Over 15% PCE improvement can be obtained in LbL and BHJ all-PSCs with CN in LbL and BHJ active layers.

Broadband photomultiplication type all-polymer photodetectors with the structure of ITO/PFN-Br/PBDB-T : PYF-T-o (3 : 100)/LiF/Au achieve EQEs of 18 000% at 360 nm and 9000% at 850 nm under 4 V, which are applied in an optical pulse counting circuit.

This review systematically summarizes the development of all-small-molecule organic photovoltaics (SMPVs) from molecule engineering and device engineering aspects, and highlights the challenges and perspectives of further developing SMPVs.

Three polymers, DCP1-3, with PC61BM pendants as intramolecular traps were carefully synthesized, and they were successfully applied in photomultiplication-type organic photodetectors (PM-OPDs) showing excellent intrinsic stability.

Charge injection is a basic transport process that strongly affects performance of optoelectronic devices such as light-emitting diodes and photodetectors. In these devices, the charge injection barrier is related to the band bending at the active layer/electrode interface and exhibits sophisticated dependence on interface structure and device operating conditions, making it difficult to determine via either theoretical prediction or experimental measurements. Here, in operando cross-sectional scanning Kelvin probe microscopy (SKPM) has been applied in organic photodetectors to visualize the interfacial band bending. The photoinduced interfacial band bending becomes more significant with increasing reverse bias voltage, resulting in reduced charge injection barrier and facilitated charge injection. The photoinduced injection current is orders of magnitude higher than the photocurrent directly generated from light absorption and thus leads to significant photomultiplication. Furthermore, the interfacial structure is tuned to further enhance photoinduced interfacial band bending and the photomultiplication factor.

Bottom surface of active layers and interface of indium tin oxide (ITO) electrodes and active layers play a crucial role in determining the performance of polymer photodetectors with photomultiplication (PM-PPDs). The interfacial trapped electron distribution closing to ITO electrodes will determine spectral response range and external quantum efficiency (EQE) of PMPPDs. The bottom interface is more sensitive than top interface when light is coming from the ITO side, and the larger density of generated charge on the bottom interfaces will induce interfacial band more bending for efficient charge tunneling injection. Highly sensitive and sub-microsecond PM-PPDs are achieved with PMBBDT:Y6 (100:7, w/w) as active layers under forward bias, yielding EQE of 18,700% at 320 nm, 21,700% at 600 nm and 16,400% at 810 nm under a bias of 7 V, respectively, as well as fast response time of 79 μs. The high EQE of the PM-PPDs is attributed to efficient hole tunneling injection from ITO electrode under forward bias. The electron traps closing to ITO electrode will be quickly filled up when light is coming from ITO side, leading to interfacial band more bending for hole tunneling injection. Importantly, the PM-PPDs is performed to measure heart rate (HR) and blood oxygen saturation (SpO2), and the measured data by the PM-PPDs are very similar with those obtained by commercial photodetectors.

All-polymer photodetectors with photomultiplication were fabricated with PMBBDT and N2200 as photoactive layers, which exhibit an external quantum efficiency of 20 700% under 4 V. The signal-to-noise ratio, linear dynamic range and specific detectivity were simultaneously enhanced by empolying a PEDOT:PSS/P-TPD double hole transport layer. An optical switch system without any current amplifier was realized.

UV-Vis-NIR broad-band organic photomultiplication-type photodetectors (OPMPDs) were fabricated with a device structure of indium tin oxide (ITO)/zinc oxide (ZnO)/(∼150 nm) active layers/Au. The active layers consisted of a 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3-undecyl-9-(undecyloxy)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[3,2-b]indole-2,10-diyl)bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H,1-diylidene))dimalononitrile (Y6-1O):5-(5-(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)-4-(2-butyloctyl)-2-yl)-8-(4-(2-butyloctyl)-5-thiophen-2-yl)dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c][1,2,5]thiadiazole (D18-Cl) (1.6 : 1, wt/wt) layer determining the spectral response range and one photomultiplication (PM) layer [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM):poly(3-hexylthiophene-2,5-diyl) (P3HT) (100 : 5, wt/wt). The spectral response of the double-layered OPMPDs was determined by the trapped-hole distribution in PC71BM:P3HT near by Au electrode, which mainly originated from the photogenerated hole in the Y6-1O:D18-Cl layer. The trapped-hole in P3HT induced interfacial band-bending for efficient electron-tunneling injection from the Au electrode. The trapped-hole-induced electron-tunneling injection could be markedly enhanced by increasing the applied voltage, leading to markedly improved external quantum efficiency (EQE) values. The double-layered OPMPDs exhibited a broad spectral response range from 300 to 1000 nm, and achieved a highly effective EQE of approximately 50 400% at 360 nm under an applied voltage of 5 V, which was the highest value among organic photodetectors (OPDs) under the same applied voltage. Moreover, the maximum specific detectivity (D*) of 3 × 1012 jones and a linear dynamic range (LDR) of 120 dB at 810 nm under an applied voltage of 5 V were achieved in the double-layered OPMPDs. This study brings forward a smart strategy to achieve high performance broad-band OPMPDs by employing double-layered thin active layers.

Photomultiplication organic photodetectors (PM-OPDs) were successfully constructed with a planar structure of PBDB-T/ITIC-Br as the active layer sandwiched by electrodes. Some isolated electron traps near the top surface of PBDB-T will be formed because small content ITIC-Br will permeate into PBDB-T layer prepared by sequential spin-coating method. The PM-OPDs achieve an external quantum efficiency (EQE) of 260% at 360 nm under a −9 V bias. The phosphorescent material FIrpic was incorporated into the PBDB-T layer to adjust the PBDB-T molecular arrangement for enhancing the hole mobility in the active layer. The optimal PM-OPDs with PBDB-T : FIrpic (100 : 10, wt/wt) display an EQE value of 2500% at 360 nm under a −9 V bias. A linear dynamic range (LDR) of 137 dB and a specific detectivity (D*) of 4.2 × 1012 Jones are also achieved in PM-OPDs with PBDB-T : FIrpic (100 : 10, wt/wt). Moreover, high-quality imaging with the PM-OPDs as photosensitive element was realized by utilizing imaging systems without current preamplifiers, indicating that the PM-OPDs have potential applications in imaging.

Over 200 nm thickness of active layers are essential for achieving efficient organic photovolatics (OPVs) using the roll-to-roll (R2R) large-scale production technology. In this study, a series of OPVs with 300 nm thick active layers were prepared with PM6:BTP-4F-12:BP-4F as active layers. The PM6:BTP-4F-12- and PM6:BP-4F-based binary OPVs achieve power conversion efficiencies (PCE) of 14.62% and 14.14%, respectively, with 300 nm thick active layers, also exhibiting complementary photovoltaic parameters. A PCE of 15.63% is achieved by the optimized ternary thick-film OPVs by combining the superiorities of two binary thick-film OPVs, deriving from a short circuit current density (JSC) of 26.57 mA cm−2, an open circuit voltage (VOC) of 0.840 V and a fill factor (FF) of 70.03%. The performance improvement of ternary thick-film OPVs should be mainly ascribed to the optimized molecular arrangement and phase separation for efficient charge transport in ternary thick active layers, which can be confirmed from the significantly improved FFs of ternary thick-film OPVs. This study indicates that the ternary strategy has great potential in preparing efficient thick-film OPVs.

Semitransparent organic solar cells (OSCs) were fabricated with a broad bandgap polymer D18-Cl as the donor (D), narrow bandgap small molecule Y6-1O as the acceptor (A) and ultra-narrow bandgap material Y6 as the third component. A power conversion efficiency (PCE) of 14.92% can be obtained from opaque OSCs with D18-Cl:Y6-1O (1.1 : 1.6, wt/wt or 0.7 : 1.6, wt/wt) as active layers, which is due to the dependence of the three well-balanced photovoltaic parameters on D18-Cl content in the active layer. It should be highlighted that the average visible transmittance (AVT) of blend films can be markedly enhanced from 30.3% to 47.3% with decrease in D:A from 1.1 : 1.6 to 0.7 : 1.6 (wt/wt), which is highly conducive to the preparation of semitransparent OSCs. Keeping the D:A as constant (0.7 : 1.6, wt/wt), 16.05% PCE is achieved in opaque ternary OSCs with D18-Cl:Y6-1O:Y6 (0.7 : 0.8 : 0.8, wt/wt) as the active layers, resulting from the slightly increased JSC of 23.21 mA cm−2 and FF of 76.74%. The AVT of the corresponding ternary blend films is also improved to 50.1%. Semitransparent ternary OSCs are fabricated with Au (1 nm)/Ag (20 nm, 15 nm, 10 nm) replacing 100 nm Ag as the electrode. A PCE of 13.02%, an AVT of 20.2% and light utilization efficiency of 2.63% are obtained from the semitransparent OSCs with Au (1 nm)/Ag (10 nm) as the electrode. This work indicates that adjusting D:A weight ratio and employing a ternary strategy should have great potential in simultaneously improving the PCE and AVT of semitransparent OSCs, especially using a wide bandgap polymer as the donor.

Broadband organic photodetectors with photomultiplication (PM-OPDs) can be realized in the device structures of ITO/PEDOT:PSS/active layers/Al, where the active layers contain one broad bandgap polymer PDBD-T and a much lower amount of the ultra-narrow bandgap material, IEICO-4F. The active layers have an efficient single carrier (hole) transport property, leading to the low dark current of the PM-OPDs. The rather low amount of IEICO-4F surrounded by PBDB-T will become some isolated electron traps due to their differences in the lowest unoccupied molecular orbital levels. The photogenerated holes will be efficiently transported along the channels formed by PBDB-T, and the photogenerated electrons will prefer to be trapped in the isolated IEICO-4F. The trapped electrons in IEICO-4F near the Al electrode will induce interfacial band bending for the hole tunneling injection, achieving the photomultiplication phenomenon. The optimal PM-OPDs with PBDB-T : IEICO-4F (100 : 3, wt/wt) as active layers exhibited an external quantum efficiency (EQE) of >100% in the spectral range from 310 nm to 850 nm. The EQE of PM-OPDs can reach 1350% at 675 nm and 400% at 850 nm under −20 V bias. The ultra-narrow bandgap material IEICO-4F plays vital roles in realizing the PM phenomenon and extending the near infrared spectral response range.

Dual molecular engineering of alkyl side chains and halogen accepting ends of asymmetric fused-ring acceptors has been proposed for controlling aggregation for optimized organic solar cells (OSCs). Fluorination or chlorination on end-capped groups are explored along with linear octyl (C8) or branched 2-butyl-1-octyl chain (BO) substitution on the donating core. The inherent features of the larger Cl atom and longer C–Cl bond markedly extend the backbone stacking area and thus enhance molecular aggregation, while bulky BO chain exert a heavier steric shielding effect on backbone stacking. Consequently, IPTBO-4Cl shows properly weakened intermolecular interaction for balanced molecular aggregation. IPTBO-4Cl when blended with a PM6 polymer donor delivers a highest power conversion efficiency (PCE) of 15% and a 72.6% fill factor (FF). Expectedly, fluorinated IPT-4F bearing shorter C8 chains outputs a good PCE nearing 15% with a 74.2% FF. To the best of our knowledge, the PCE of 15% is by far the highest for asymmetric FRA based OSCs. By contrast, IPT-4Cl and IPTBO-4F with either excessively strong or weak aggregation result in relatively low photovoltaic performance. Our results demonstrate controlling aggregation via delicate molecular engineering is an undeniably effective way to achieve efficient OSCs.

A new zinc porphyrin, named as Por4IC, was synthesized, which through extension of conjugation and an enhancement of planarity and donor–acceptor interactions exhibits a very low band gap. The molecule was able to efficiently facilitate a photomultiplication effect in blend with P3HT which was assisted by electron trapping followed by hole tunneling injection from the Al electrode giving rise to a high external quantum efficiency of 22 182% and a specific detectivity of 4.4 × 1012 Jones at 355 nm and at −15 V bias. This work introduces porphyrin derivatives as promising dopants for photomultiplication type photodetectors.

Due to their unique merits, asymmetrical fused-ring electron acceptors (FREAs) have received increasing attention in the field of organic photovoltaics (OPVs). Herein, we designed and synthesized an asymmetrical FREA, namely AY6, by employing a cross-conceptual strategy which combines the structural features of asymmetrical IT6-4F with high-performance Y6. Compared to Y-shape Y6, X-shape AY6 shows poor crystallization properties and thus a significantly blue-shifted absorption. However, it is precisely because of this unfavorable self-stacking effect that AY6 has an opportunity to pack with PM6 and form a new intermixed phase. As a result, the PM6:AY6 blend film exhibits a perfect face-on orientation with stronger π–π stacking than the PM6:Y6 blend film, which facilitates efficient exciton dissociation and balanced carrier transport, and therefore higher FF. In general, such a cross-conceptual design strategy is an effective method which not only boosts the efficiency of asymmetrical FREA-based OSCs but also increases the fill factors of OSCs based on Y6-like FREAs.

Ternary organic photovoltaics (OPVs) are fabricated with PBDB-T-2Cl:Y6 (1:1.2, wt/wt) as the host system and extra PC71BM as the third component. The PBDB-T-2Cl:Y6 based binary OPVs exhibit a power conversion efficiency (PCE) of 15.49% with a short circuit current ( J SC) of 24.98 mA cm−2, an open circuit voltage ( V OC) of 0.868 V and a fill factor (FF) of 71.42%. A 16.71% PCE is obtained in the optimized ternary OPVs with PBDB-T-2Cl:Y6:PC71BM (1:1.2:0.2, wt/wt) active layer, resulting from the synchronously improved J SC of 25.44 mA cm−2, FF of 75.66% and the constant V OC of 0.868 V. The incorporated PC71BM may prefer to mix with Y6 to finely adjust phase separation, domain size and molecular arrangement in ternary active layers, which can be confirmed from the characterization on morphology, 2D grazing incidence small and wide-angle X-ray scattering, as well as Raman mapping. In addition, PC71BM may prefer to mix with Y6 to form efficient electron transport channels, which should be conducive to charge transport and collection in the optimized ternary OPVs. This work provides more insight into the underlying reasons of the third component on performance improvement of ternary OPVs, indicating ternary strategy should be an efficient method to optimize active layers for synchronously improving photon harvesting, exciton dissociation and charge transport, while keeping the simple cell fabrication technology.

Nonfullerene acceptors (MQ3, MQ5, MQ6) are synthesized using asymmetric and symmetric ladder-type heteroheptacene cores with selenophene heterocycles. Although MQ3 and MQ5 are constructed with the same number of selenophene heterocycles, the heteroheptacene core of MQ5 is end-capped with selenophene rings while that of MQ3 is flanked with thiophene rings. With the enhanced noncovalent interaction of O⋅⋅⋅Se compared to that of O⋅⋅⋅S, MQ5 shows a bathochromically shifted absorption band and greatly improved carrier transport, leading to a higher power conversion efficiency (PCE) of 15.64 % compared to MQ3, which shows a PCE of 13.51 %. Based on the asymmetric heteroheptacene core, MQ6 shows an improved carrier transport induced by the reduced π-π stacking distance, related with the increased dipole moment in comparison with the nonfullerene acceptors based on symmetric cores. MQ6 exhibits a PCE of 16.39 % with a VOC of 0.88 V, a FF of 75.66 %, and a JSC of 24.62 mA cm-2 .

Photomultiplication (PM) type all-polymer photodetectors (all-PPDs) are first demonstrated with the sandwich structure of ITO/PEDOT:PSS/PBDB-T:PZ1 (100: x , wt/wt)/Al. The optimal PM type all-PPDs with PBDB-T:PZ1 (100:3, wt/wt) as active layers exhibit external quantum efficiency (EQE) of >100% in the spectral range from 310 to 790 nm. Under 675 nm light illumination, the champion EQE value arrives to 1,470% at −20 V bias and the specific detectivity approaches 1× 1012 Jones at −10 V bias. The PM phenomenon in all-PPDs results from hole tunneling injection assisted by interfacial band bending induced by trapped electrons in PZ1 near Al electrode. The EQE values of optimal PM type all-PPDs still remained over 90% of the original value after 60 d of the storage in a high-purity nitrogen-filled glove box.

Organic photovoltaics (OPVs) were fabricated with J71, PBT1-C or their blends as donor and IT-2F as acceptor. The power conversion efficiency (PCE) of J71 and PBT1-C based binary OPVs arrive to 10.45% and 10.23%, respectively. Although the very similar photovoltaic performance of two binary OPVs, three photovoltaic parameters are distinctly different. Meanwhile, three materials also exhibit complementary absorption range to cover solar light as wide as possible. Integrating the advantages of materials and binary OPVs, the optimized ternary OPVs are obtained with 12.26% PCE and 75.53% fill factor by incorporating 20 wt% PBT1-C in donors. The enhanced photovoltaic performance should result from enhanced photon harvesting and optimized phase separation. The two polymer donors should prefer to form alloyed state, which can reasonably interpret the enhanced photovoltaic performance of ternary OPVs with PBT1-C content from 10 wt% to 50 wt% in donor.

Photomultiplication (PM) type organic photodetectors (OPDs) with two detection windows were fabricated with a specific structure of ITO/PDIN/active layers/semitransparent Al, only holes can be transported in the active layers with 100:1 wt ratio of P3HT to PC61BM. The specific structure makes the PM type OPDs working under top/bottom light illumination and forward/reverse bias conditions, exhibiting a tunable spectral response range. The rather less PC61BM may prefer to be surrounded by P3HT to form some isolated electron traps in the active layers, which is beneficial to decreasing the dark current density (JD) of OPDs with hole-only transport channels provided by P3HT. Under dark condition, holes are hardly injected from ITO/PDIN or Al electrode to the highest occupied molecular orbits (HOMO) of P3HT due to the large interfacial injection barriers, resulting in the rather low JD. Holes can be easily injected from electrodes due to the trap-assisted interfacial band bending under light illumination conditions. The external quantum efficiency (EQE) spectra of PM type OPDs are determined by the photogenerated electron distribution on the cross-section near electrode, which can be well supported by the corresponding simulation results based on transfer matrix method. The PM type OPDs integrated with two detection windows exhibit broadband and narrowband response range under forward or reverse bias, which should have great potential in the integrated optoelectronic products, especially in the field of artificial intelligence.

Polymer solar cells (PSCs) were fabricated with PTB7-Th as donor and fluorinated non-fullerene materials IEICO-4F, IT-4F or their mixture as acceptor. Binary PSCs with IEICO-4F or IT-4F as acceptor exhibit a power conversion efficiency (PCE) of 10.74% or 8.81% and fill factor (FF) of 63.32% or 73.90%, respectively. The PCE of 11.78% is achieved for the optimized ternary PSCs with 25 wt% IT-4F in acceptors, resulting from over 12.3% FF improvement (71.12% vs 63.32%). The distinguished FF improvement should be attributed to the optimized molecular arrangement and phase separation scale by incorporating the third component as morphology regulator. This work provides an efficient strategy on selecting materials for achieving efficient ternary PSCs by combining the superior photovoltaic parameters of two corresponding binary PSCs, in addition to the used materials with complementary absorption spectra.

Opaque and semitransparent polymer solar cells (PSCs) were prepared with the narrow band gap donor PTB7-Th and the ultra-narrow band gap acceptor IEICO-4F by optimizing their doping ratios. The power conversion efficiency (PCE) of opaque PSCs can be maintained at over 11% by altering PTB7-Th : IEICO-4F ratios from 1.4 : 1.5 to 0.8 : 1.5 (wt/wt), along with a red-shifted absorption edge of active layers. The red-shifted absorption edge should be attributed to IEICO-4F molecular aggregation due to the relatively increased IEICO-4F content in active layers. The increased photon harvesting in the near infrared light range due to IEICO-4F molecular aggregation and decreased photon harvesting in the visible light range with lower PTB7-Th content provide great potential to prepare efficient semitransparent PSCs. The semitransparent PSCs were prepared with 1 nm Au/11 nm Ag replacing 100 nm Al as the electrode. The average visible transmittance (AVT) of semitransparent PSCs is increased from 23.7% to 27.1% by decreasing the PTB7-Th content in active layers, along with a slight PCE decrease from 9.48% to 9.06% and a lower cost. The optimized 9.06% PCE and 27.1% AVT should be impressive values for semitransparent PSCs. This work may provide a smart strategy to achieve efficient semitransparent PSCs with low cost by decreasing the narrow band gap donor content in active layers.

Perovskite photodetectors (PPDs), which combine the advantages of perovskite semiconductor materials with superior optical and electronic properties and solution-processed manufacturing, have emerged as a new class of revolutionary optoelectronic devices with potential for various practical applications. Encouraged by the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of perovskite materials with interesting optoelectronic properties, increasing research attention is focused on the development of high performance PPDs. In this review, the recent progress on emerging PPDs is comprehensively summarized from the perspective of device physics and materials science. The strategies for extending the spectral response range of PPDs and improving the performance of devices are investigated. Furthermore, the methods for realizing narrowband photodetectors are also discussed, where filter-free and self-filter narrowband PPDs are achieved based on the concept of charge collection narrowing. Meanwhile, the promising future directions in this research field are proposed and discussed, including multifunctional PPDs, perovskite–organic hybrid photodetectors, flexible and transparent PPDs, self-powered PPDs, and photodetector systems and arrays. This review provides valuable insights into the current status of highly sensitive PPDs and will spur the design of new structures and devices to further enhance their photo-detection performances and meet the need of versatility in practical application.

The power conversion efficiency (PCE) of 13.00% was achieved in PBDB-T:Y16-based polymer solar cells (PSCs). On this basis, PCE of ternary PSCs was improved to 14.11% by incorporating 15 wt% MeIC1 in acceptors, resulting from simultaneously enhanced short circuit current (JSC) of 22.76 mA cm−2 and fill factor (FF) of 68.22%. The observed 14.11% PCE is among the highest values for all ternary PSCs. Y16 and MeIC1 preferred to form an alloyed acceptor due to good compatibility, which is beneficial to the formation of efficient electron transport channels in ternary active layers. Photon harvesting, exciton dissociation and charge transport could be synergistically optimized by incorporating 15 wt% MeIC1 in the acceptors. The optical field and photogenerated exciton distribution in active layers were calculated according to their intrinsic properties, which could provide more intuitive evidence of JSC and FF improvement. The photogenerated exciton distribution in active layers could also be optimized by employing a ternary strategy, which was beneficial for better balance charge collection efficiency and for achieving high FF of the ternary PSCs. This work further demonstrates that ternary strategies have great potential for improving the PSC performance by simultaneously optimizing photon harvesting and photogenerated exciton distribution in active layers.

Zero-dimensional (0D) perovskites have attracted a great deal of attention over the last few years due to their fascinating properties. However, their application in electroluminescent (EL) light-emitting diodes (LEDs) is limited and suffering from extremely low device performance. Herein, the nonluminescent Cs4PbBr6 nanocrystals (NCs) were successfully transformed to highly luminescent Zn-doped CsPbBr3/Cs4PbBr6 NCs via an insertion reaction with ZnBr2, which changed the atomic molar ratios of NCs and promoted the formation of CsPbBr3. In this reaction, the Zn2+ ions provided by ZnBr2 together with the Pb2+ ions can occupy the B-site due to the similar ion radius. The extra Br- ions not only can facilitate the transformation process, but also can passivate the surface defects of the NCs, resulting in high photoluminescence quantum yield (PL QY) of 77.5%. Furthermore, as-synthesized Zn-doped CsPbBr3/Cs4PbBr6 NCs were used as emitters to fabricate EL LEDs. The device achieved the maximum current efficiency of 9.8 cd/A and a peak external quantum efficiency of 3.2%, which is the best performance of the CsPbBr3/Cs4PbBr6 based LEDs. This reveals the great application potential of CsPbBr3/Cs4PbBr6 NCs as EL emitters in LEDs.

With the sharp growth of non-fullerene acceptors, it is still challenging to develop new polymer donors for highly efficient polymer solar cells (PSCs). Here, a series of metallated terpolymer donors PM6Irx (x = 1%, 3%, 5%) are synthesized by incorporating a new iridium complex, named M1, into the backbone of the state-of-the-art polymer PM6. The M1 shows a strong absorption in the visible region, which is beneficial to enhance photon harvesting in the active layer. The PM6Ir1:Y6 based PSCs exhibit the best power conversion efficiency (PCE) of 16.71% with short-circuit current density (JSC) of 26.16 mA cm−2, open-circuit voltage (VOC) of 0.848 V and fill factor (FF) of 75.33%. A PCE improvement of about 7% is achieved compared with PM6Ir0:Y6 based control device with PCE of 15.65%, which is due to the markedly increased JSC and FF. The introduction of a moderate amount of M1 enhances the photon harvesting, triplet excitons and lifetime, charge mobility as well as optimizes the active layer morphology. This work indicates that iridium complexes with strong absorption in the visible region have a great potential to promote the photovoltaic performance.

Ternary-blend organic solar cells (TOSCs) are fabricated with PM6:BTP-4F-12 as the host system and IT-M as the third component. The third component IT-M takes multiple roles in improving performance of TOSCs through reducing energy-loss of the optimized TOSCs, optimizing molecular arrangement and phase separation in active-layers. The well optimized molecular arrangement and phase separation can be beneficial to charge separation and transport in TOSC, which can be confirmed by the characterization of 2D grazing incidence wide-angle X-ray scattering, transmission electron microscopy, magneto-photocurrent, as well as electrochemical impedance spectroscopy. By finely optimizing IT-M content, a power-conversion-efficiency (PCE) of 17.71% is achieved in the optimized TOSCs, benefiting from simultaneously enhanced short-circuit-current density (JSC) of 25.95 mA cm−2, open-circuit-voltage (VOC) of 0.875 V and fill-factor (FF) of 78.02% in comparison with the OSCs with PM6:BTP-4F-12 as active-layers. Furthermore, average PCE over 15% can be achieved from twenty individual TOSCs with active-layer thickness of 300 nm, indicating the optimized TOSCs have excellent thickness tolerance.

Photomultiplication type polymer photodetectors (PM-PPDs) were achieved with PBDB-T:BTPV-4F (98:2, wt/wt) as blend active layer based on a sandwich structure. Isolated electron traps are formed due to the rather less BTPV-4F surrounded by PBDB-T in blend active layers. Trapped electrons in BTPV-4F near Al electrode will induce interfacial band bending for hole tunneling injection into blend active layers. The tunneling injected holes will be transported along the channels formed by PBDB-T in blend active layers, photomultiplication phenomenon will be obtained when the number of holes crossing through blend active layers is larger than that of incident photons per unit time. Liquid crystal material BTR was selected as regulator to adjust PBDB-T molecular arrangement for improving hole mobility in blend active layers, leading to optimized performance of PM-PPDs. Optimal PM-PPDs were obtained with PBDB-T:BTR:BTPV-4F (89:9:2, wt/wt/wt) as blend active layer. The external quantum efficiency (EQE) values of optimal PM-PPDs are 1.5 times that of PM-PPDs based on PBDB-T:BTPV-4F (98:2, wt/wt) in the whole spectral response range under −10 V applied bias. The EQE of optimal PM-PPDs can be markedly improved by increasing applied bias, which is improved from 600% to 19,300% at 660 nm with applied bias increased from −10 to −20 V. The responsivity of optimal PM-PPDs arrives to 102 A W−1 at 660 nm under −20 V applied bias.

Epigallocatechin gallate (EGCG) has been regarded as a protective bioactive polyphenol in green tea against nonalcoholic steatohepatitis (NASH), but the mechanism remains poorly deciphered. Herein, we assessed the role and mechanism of EGCG on gut microbiota and the metabolism in NASH development. Forty-eight male C57BL/6J mice were fed with either a methionine-choline-sufficient diet or a methionine-choline-deficient (MCD) diet with or without EGCG administration for 4 weeks. Liver injury, inflammation, lipid accumulation, and iron overload were examined. 16S ribosomal RNA sequencing was used to detect the fecal microbiome. In our research, we observed that EGCG notably improved MCD-diet-derived gut microbiota dysbiosis, as proved by a distinctively clustered separation from that of the MCD group and by the decrease of the Oxalobacter, Oscillibacter, Coprococcus_1, and Desulfovibrio genera and enrichment of norank_f__Bacteroidales_S24_7_group, Alloprevotella, and Bacteroides. Spearman-correlation heatmap analysis indicated that Bacteroides and Alloprevotella induced by EGCG were strongly negatively correlated with lipid accumulation. Functional enzymes of the gut microbiome were predicted by PICRUSt based on the operation classification unit. The results revealed that 1468 enzymes were involved in various metabolic pathways, and 371 enzymes showed distinct changes between untreated and EGCG-treated mice. Long-chain-fatty-acid-CoA ligase ACSBG played a distinct role in fatty acid metabolism and ferroptosis and was significantly negatively correlated with Bacteroides. Altogether, the salutary effect of EGCG on NASH might be via shifting gut flora and certain enzymes from genera. Our study thus takes a step toward NASH prevention and therapy.

In this paper, we report a facile route to synthesize mitochondria-targeted core–shell nanoparticles (NPs). Firstly, PLL-coated NPs are prepared by a one-step reprecipitation-encapsulation method assisted by positively charged poly-L-lysine (PLL). The effect of the molecular weight of PLL on the formation of particles is studied in terms of morphology, size and zeta potential, and medium-sized PLL (MH-PLL) is proved to be the optimum one. By means of crosslinking with different amounts of glutaraldehyde, amino groups in MH-PLL-NPs are characterized by zeta potential and fluorescamine assay, respectively. The results indicate that in the PLL shell, only a small portion of amino groups (surface amino groups, SAGs) are available for conjugation, while the other groups exclusively contribute to zeta potential. Subsequently, a known mitochondriotropic ligand, triphenylphosphonium (TPP), is conjugated with SAG via a carbodiimide reaction, which is evaluated by NMR and absorption spectra, respectively. The TPP-MH-PLL-NPs exhibit a low cytotoxic effect tested by the MTT method, as well as efficient cellular uptake microscopically observed after a fluorescent dye, coumarin 6, is incorporated. Most importantly, the TPP-conjugated NPs can selectively target mitochondria, demonstrated by the merged z-stacked images in co-localization experiments with MitoTracker-stained mitochondria. Given that many hydrophobic species could be loaded into the particle core, TPP-MH-PLL-NPs are very promising as mitochondria-targeted nanocarriers for imaging or anti-cancer therapies.

Efficient ternary organic photovoltaics (OPVs) are fabricated with two polymer materials PF2 and J71 as donors and Y6 as the acceptor. The PF2 and J71 based binary OPVs exhibit 10.26% and 9.56% power conversion efficiency (PCE), respectively. Even with similar highest occupied molecular orbital (HOMO) energy levels of PF2 and J71, the J71 based binary OPVs show a relatively high open circuit voltage (VOC) of 0.86 V compared with 0.71 V for PF2 based binary OPVs. The VOCs of ternary OPVs monotonously increased with the increase of J71 content in donors, which should be mainly ascribed to the reduced energy loss according to the VOCs of two binary OPVs and the HOMO energy levels of two donors. The short circuit current density (JSC) and fill factor (FF) of ternary OPVs can also be simultaneously enhanced with the J71 content up to 30 wt% in donors, leading to 12.12% PCE of the optimized ternary OPVs with a JSC of 24.97 mA cm−2, a FF of 64.70% and a VOC of 0.75 V. Reducing energy loss by the ternary strategy is rarely reported in the literature, which should also be an efficient method to realize performance improvement of OPVs.

Efficient organic solar cells (OSCs) are fabricated using polymer PM6 as donor, and IPTBO-4Cl and MF1 as acceptors. The power conversion efficiency (PCE) of IPTBO-4Cl based and MF1 based binary OSCs individually arrive to 14.94% and 12.07%, exhibiting markedly different short circuit current density (JSC ) of 23.18 mA cm-2 versus 17.01 mA cm-2 , fill factor (FF) of 72.17% versus 78.18% and similar open circuit voltage (VOC ) of 0.893 V versus 0.908 V. The two acceptors, IPTBO-4Cl and MF1, have similar lowest unoccupied molecular orbital levels, which is beneficial for efficient electron transport in the ternary active layer. The PCE of optimized ternary OSCs arrives to 15.74% by incorporating 30 wt% MF1 in acceptors, resulting from the simultaneously increased JSC of 23.20 mA cm-2 , VOC of 0.897 V, and FF of 75.64% in comparison with IPTBO-4Cl based binary OSCs. The gradually increased FFs of ternary OSCs indicate the well-optimized phase separation and molecular arrangement with MF1 as morphology regulator. This work may provide a new viewpoint for selecting an appropriate third component to achieve efficient ternary OSCs from materials and photovoltaic parameters of two binary OSCs.

A series of polymer solar cells (PSCs) were prepared with different solvent additive 1-chloronaphthalene (CN) doping volume ratio to adjust the phase separation of active layers. The optimized PSCs exhibit a power conversion efficiency (PCE) of 8.09%, along with an open-circuit voltage of 1.01 V, a short circuit current density of 13.64 mA cm–2, and a fill factor of 58.70%. All the key photovoltaic parameters of PSCs can be simultaneously increased by incorporating 1.0 vol % CN in blend solutions due to the optimized phase separation of active layers assisted by the volatilization of CN. Over 24% PCE improvement can be obtained by incorporating 1.0 vol % CN, indicating that the dynamic process of film forming should play the vital role in determining the performance of PSCs.

Isomers with small structural changes usually exhibit different properties. Rationally designing isomers of some high-performance SMAs can further enhance their function. In this work, an asymmetrical small molecule acceptor (SMA) MeIC1 isomerized from MeIC is reported. Compared with the symmetrical MeIC, the asymmetrical isomer showed almost the same absorption range but an elevated LUMO energy level and simultaneously enhanced π–π stacking and electron mobility by replacing the thieno[3,2-b]thiophene unit with a larger sized dithieno[3,2-b:2′,3′-d]thiophene unit in the ladder-type core of MeIC. As a result, the MeIC1-based PSCs achieved a higher PCE up to 12.58% with a promoted Voc and Jsc and an unchanged FF compared with those of MeIC-based PSCs when blended with PBDB-T. This work reveals that asymmetrical isomerization is effective for PCE promotion.

Two new non-fullerene (NF) acceptors, namely BDTIT-M and BDTThIT-M, were rationally designed to optimize the energy levels and optical bandgap. BDTIT-M is derived by changing the end-group of NFBDT into slightly weak DCI-M, and BDTThIT-M is obtained by adding two conjugated thiophene side-chains into a ladder-type core of BDTIT-M. By incorporating with the polymer donor PBDB-T, BDTIT-M based organic solar cells (OSCs) deliver a higher PCE of 11.31% compared to that of NFBDT based cells, which is mainly attributed to the increased VOC and FF. A higher PCE of 12.12% with a small energy loss of ∼0.588 eV is achieved compared with BDTThIT-M based OSCs, benefiting from the elevated LUMO level, narrowed bandgap, and enhanced absorption coefficient and electron mobility of BDTThIT-M compared with BDTIT-M. The combination of a methyl-modified end-group and conjugated side-chain should be an efficient strategy to elevate the LUMO and HOMO levels with different amplitudes for realizing simultaneous improvement in VOC and JSC.

In this work, we present a structurally defined blue-shift non-fullerene electron acceptor (ITCT) matching with PTB7-Th as the electron donor for high-performance fullerene-free polymer solar cells (PSCs). The PTB7-Th/ITCT blend based bulk-heterojunction (BHJ) devices give an appreciable PCE of 8.23% and a relatively high VOC of 0.96 V without any optimization. Upon device processing with thermal annealing and the addition of 0.1% DIO additive, the active layer achieves a more ordered and crystalline morphology. Consequently, a high PCE of 10.42% has been achieved with a VOC of 0.95 V, a JSC of 15.13 mA cm−2 and a high FF of 0.72. To the best of our knowledge, the PCE of 10.42% is among the highest values reported in the literature to date for non-fullerene PSCs using PTB7-Th as the electron donor.

One narrow bandgap donor (PTB7-Th) and two ultra-narrow bandgap acceptors (COi8DFIC and IEICO-4F) were elaborately selected to fabricate semitransparent ternary polymer solar cells (PSCs). To find out the optimal content of IEICO-4F in the acceptors, a series of opaque PSCs were first fabricated with 100 nm of Ag as the electrode. The power conversion efficiency (PCE) of the optimized opaque ternary PSCs arrived at 11.94% by incorporating 15 wt% IEICO-4F in the acceptors. Then, the thickness of Ag was adjusted to balance its electrical conductivity and transmittance, and the 100 nm of Ag was replaced by 15 nm of Ag as a semitransparent electrode. The semitransparent electrode possesses high transmittance in the visible light range and low transmittance in the long wavelength range, which is propitious for photon harvesting of ternary active layers with two ultra-narrow bandgap acceptors. The optimized semitransparent ternary PSCs show a synchronously improved PCE of 8.23% and an average visible transmittance (from 370 nm to 740 nm) of 20.78% compared with COi8DFIC based semitransparent binary PSCs. This work suggests the potential of a ternary strategy for fabricating highly efficient semitransparent PSCs with narrow or ultra-narrow bandgap materials as active layers.

To develop new central core structure, we designed and synthesized a naphthalene-fused octacyclic electron-rich block, named as NITT. With the NITT ladder-type core and two distinct terminal groups (IC-2F and CPTCN-Cl), two novel A-D-A-type non-fullerene acceptors (NFAs), namely NITT-BF and NITT-ThCl, were constructed. Two NFAs exhibit broad and intense absorption and high electron mobility due to the coplanar architecture. When blended with polymer donor PM6, NITT-BF-based device acquires more favorable morphology, higher exciton dissociation and charge collection efficiency, and higher and more balanced hole/electron mobilities, resulting in the significantly improved short-circuit current density (JSC) of 18.08 mA cm−2 and fill factor (FF) of 72.38%. Additionally, both NITT-BF- and NITT-ThCl-based devices deliver very high open-circuit voltages (VOCs) (0.94 V for NITT-BF-based device and 0.97 V for NITT-ThCl-based device). Therefore, PM6:NITT-BF-based device yields an optimal PCE of up to 12.30%, which is much higher than that of PM6:NITT-ThCl-based device (9.58%). Notably, the high PCE of 12.30% is one of the best values for naphthalene-fused NFAs in organic solar cells (OSCs). These results indicate that the linear ladder-type NITT is a promising electron-donating core for constructing high-performance NFAs and terminal strategy is a good way to further boost the photovoltaic performance of OSCs.

Although the rapid development of polymer solar cells (PSCs) has been achieved, it is still a great challenge to explore efficient ways for improving power conversion efficiency (PCE) of PSCs from materials and device engineering. Ternary strategy has been confirmed as an efficient way to improve PCE of PSCs by employing three kinds of materials. In this work, one polymer donor PM6, and two non-fullerene materials N3 and MF1 are selected to prepare ternary PSCs with layer-by-layer (LbL) or bulk-heterojunction (BHJ) structure. The LbL and BHJ-PSCs exhibit PCEs of 16.75% and 16.76% with 15 wt% MF1 content in acceptors, corresponding to over 5% or 4% PCE improvement compared with N3-based binary PSCs with LbL or BHJ structure. The PCE improvement is mainly attributed to the fill factor enhancement from 73.29% to 76.95% for LbL-PSCs or from 74.13% to 77.51% for BHJ-PSCs by employing the ternary strategy. This work indicates that ternary strategy has great potential in preparing highly efficient LbL-PSCs via simultaneously optimizing molecular arrangement and the thickness of each layer.