•Exciplex-based OLEDs are fabricated with TAPC as the donor and a series triazine derivatives as the acceptors.•Electrical and optical properties of the devices are systematically investigated.•The efficiency of the devices is primarily determined by the photoluminance quantum yield of the emitting layers.•An efficiency roll-off less than 20% is observed for all the devices.In this work, exciplex-based OLEDs (ExOLEDs) are fabricated with 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) as the donor and a series triazine derivatives, e.g., 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), 2,4,6-tris(3-(1H-pyrazol-1-yl)phenyl)-1,3,5-triazine (3P-T2T), and 2,4,6-tris(m-(diphenylphosphinoyl)phenyl)-1,3,5-triazine (PO-T2T), as the acceptors. With different acceptors and mole ratios of donor:acceptor, the effects of the photoluminescence quantum yield (PLQY), charge carrier balance, and exciton lifetime on the EQE and efficiency roll-off are systematically investigated. It is found that the external quantum efficiency (EQE) of the ExOLEDs is primary determined by the PLQY of the mixed donor:acceptor film and tuned in a certain extent by the charge carrier balance. Furthermore, the efficiency roll-offs of different ExOLEDs are all less than 20%, which are simultaneously determined by the photoluminescence (PL) lifetime and the charge carrier balance.

Graphene oxide sheets (GOSs) are introduced between indium tin oxide (ITO) and CH3NH3PbI3 in inverted hole-transport layer-free planar heterojunction perovskite solar cells. The concentration of the GOSs is extremely low and they are sporadically covered on the ITO substrates. Combined with the high resistance of these GOSs, they cannot be regarded as an interface layer. However, the GOSs can act as the nucleation sites in the crystal growth process of CH3NH3PbI3 films, which results in dramatically improved morphology and crystallization of the CH3NH3PbI3 films. As a result, the performance of the devices is significantly improved as compared with the reference device. The optimized device shows a power conversion efficiency of 6.62%, which is about 40% higher than the reference devices. This improvement is attributed to the increased charge carrier transporting property and reduced charge carrier recombination in the CH3NH3PbI3 films.

Three novel neutral tricarbonyl rhenium(I) [Re(I)] complexes (Re-PTIP, Re-TPIP and Re-TTIP) with donor–acceptor structures were designed and synthesized. Their photophysical and electrochemical properties were investigated in detail. These Re(I) complexes showed an orange emission with a high photoluminescence quantum efficiency of 9–18%. Organic light-emitting diodes (OLEDs) with the structure ITO/2-TNATA (4,4′,4′′-tris(N-(naphthalen-2-yl)-N-phenyl-amino)triphenylamine, 5 nm)/NPB (1,4-bis[(1-naphthylphenyl)amino]-biphenyl, 40 nm)/TCTA (4,4′,4′′-tris(N-carbazolyl)tri phenylamine, 10 nm)/CBP (4,4′-bis(carbazol-9-yl)biphenyl): 8% Re(I) complex (30 nm)/Bepp2 (bis[2-(2-hydroxyphenyl)-pyridine]beryllium, 40 nm)/LiF (0.5 nm)/Al (100 nm) were fabricated to evaluate the potential application of these Re(I) complexes. Excellent device performances (current efficiency: 26.0–36.5 cd A−1, power efficiency: 20.1–31.7 lm W−1 and external quantum efficiency: 9.8–12.0%) were achieved. In particular, OLEDs with Re-TTIP as the dopant emitter showed the best performance with a maximum current efficiency of 36.5 cd A−1, a maximum power efficiency of 31.7 lm W−1 and a maximum external quantum efficiency of 12.0% with low efficiency roll-off, which were among the best data for the Re(I)-based OLEDs reported so far. Our findings indicate the great potential of neutral tricarbonyl Re(I) complexes as phosphorescent emitting materials in OLEDs.

•MoO3 layer is introduced to planar CH3NH3PbI3 photodetector.•Perovskite/electrode contact can be modified by MoO3 layer.•The optimized device achieves a two times ON/OFF ratio compared with the reference device.•The rise and decay time reduce to 21.6 and 9.9 ms, respectively.Planar CH3NH3PbI3 perovskite based photodetectors are fabricated by a facile and low-cost one-step method. The devices show broad spectral photoresponse from the ultraviolet to whole visible region and the performance can be significantly improved by the introduction of a bipolar transporting MoO3 interface layer between CH3NH3PbI3 film and Au electrode. The photocurrent of the device with an optimized MoO3 layer is about twice that of the reference device without MoO3 layer, which results in a high ON/OFF current ratio of 5.9 × 103 at 5 V. Besides, slightly increased photoresponse speed is also found in the optimized device with rise time and decay time of 21.6 and 9.9 ms, respectively. The improvement can be attributed to the improved hole and electron collection efficiency and the quickly filled in or emptied trap states at the CH3NH3PbI3/Au interface due to the introduction of the bipolar transporting MoO3 layer.Download high-res image (235KB)Download full-size image

•Photomultiplication-type photodetectors based on perovskite are fabricated.•The performance of the device is improved by introduction of suitable interface layers.•A broadband response with a high photocurrent gain of about 177 at −1 V is achieved.•The detectivity reaches 4.6 × 1013 Jones at −1 V.Organic-inorganic hybrid perovskites have attracted more attention as successful light harvesting materials for solution-processed semiconductors and exhibit remarkable optoelectronic properties. Here photomultiplication-type photodetectors based on perovskite CH3NH3PbI3 are demonstrated. By introducing suitable interlayers at the CH3NH3PbI3/electrode interfaces, the performance of the photodetector is significantly improved. The optimized device with a N,N′-di(naphthalene-1-yl)-N,N′-diphenylbenzidine anode interface layer and [6,6]-phenyl-C60-butyric acidmethyl ester cathode interface layer shows a broadband response with a high photocurrent gain of about 177 and a high detectivity of 4.6 × 1013 Jones, which are higher than the reference device. Besides, the response speed of the device is also increased. The improvement is attributed to the improved charge carrier collection efficiency and suppressed dark current of the device.Download high-res image (254KB)Download full-size image

•Au and Ag mix NPs are codeposited on indium-tin-oxide substrates by thermal evaporation method.•Cooperative plasmon enhanced small molecule organic solar cells are fabricated based on Au:Ag NPs.•A 22.5% enhancement in PCE is demonstrated.•The improvement is contributed to the increased Jsc and the increased conductivity of the device.•Factors are investigated to determine the PCE of cooperative plasmon enhance organic solar cells.Cooperative plasmon enhanced small molecule organic solar cells are demonstrated based on thermal coevaporated Au and Ag nanoparticles (NPs). The optimized device with an appropriate molar ratio of Au:Ag NPs shows a power conversion efficiency of 3.32%, which is 22.5% higher than that of the reference device without any NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au:Ag NPs and the increased conductivity of the device. Besides, factors that determining the performance of the Au:Ag NPs cooperative plasmon enhance organic solar cells are investigated, and it finds that the thickness of MoO3 buffer layer plays a crucial role. Owing to the different diameter of the thermal evaporated Au and Ag NPs, a suitable MoO3 buffer layer is required to afford a large electromagnetic enhancement and to avoid significant exciton quenching by the NPs.Download high-res image (144KB)Download full-size image

•F16CuPc is used for the first time in PSCs.•F16CuPc show good electron transport property and stability.•Fullerene-free planar PSCs exhibit highest PCE of 12.62%.High-efficiency fullerene-free planar perovskite solar cells (PSCs) consisting of hexadecafluorophthalocyaninatocopper (F16CuPc) as electron conductors are firstly reported. In the condition of using F16CuPc as a direct replacement for fullerene that universally employed in planar PSCs with an architecture of ITO/hole transport layer (HTL)/perovskite/electron transport layer (ETL), PSCs exhibit quite satisfactory photovoltaic performances. The best PSC with F16CuPc ETL presents a power conversion efficiency of 12.62% with a short-circuit current density (JSC) of 19.97 mA/cm2, an open-circuit voltage (VOC) of 0.93 V and a fill factor (FF) of 0.68. Such performance is comparable to the C60-based PSCs and higher than that of the PCBM-based PSCs.

•TADF OLEDs are demonstrated based on exciplex formed between commercially available TAPC and T2T.•The device shows a highest EQE of 11.6%.•A low efficiency roll-off is also demonstrated.•The low efficiency roll-off is attributed to the short lifetime of delayed fluorescence and the small singlet-triplet splitting.Highly efficient thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) based on exciplex are demonstrated in a blended system with commercially available 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) and 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T). By well adjusting the ratio between these two materials, the optimized device shows a low turn-on voltage of 2.4 V and a high external quantum efficiency (EQE) of 11.6%. More importantly, the device retains an EQE of 9.4% even at a high luminescence of 1000 cd/m2. The low efficiency roll-off is attributed to the small singlet-triplet splitting and the short of the delayed fluorescence lifetime. Both EQE and efficiency roll-off are ones of the best performance among the reported TADF OLEDs based on exciplex.

•Au NPs are deposited on indium-tin-oxide substrates by thermal evaporation method.•All thermal evaporated surface plasmon enhanced OSCs are fabricated by using these Au NPs.•A 14% enhancement in PCE is demonstrated.•The improvement is attributed to the increased absorption due to LSPR of Au NPs and the conductivity of the devices.Au nanoparticles (NPs) are fabricated on indium-tin-oxide substrates by a thermal evaporation method and incorporated to an efficient small molecule organic solar cell (OSC). This renders an all thermal evaporated surface plasmon enhanced OSC. The optimized device shows a power conversion efficiency of 3.40%, which is 14% higher than that of the reference device without Au NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au NPs and the increased conductivity of the device.

•TiO2/MoO3 Core/shell NPs with size of about 40 nm are prepared.•Inverted planar perovskite solar cells with TiO2/MoO3 NPs doped PEDOT:PSS HTLs are fabricated.•A highest PCE of 13.63% is obtained.•Superior stability is also found for the devices stored in ambient conditions.We demonstrate improved performance of inverted planar heterojunction CH3NH3PbI3-xClx perovskite solar cells with a TiO2/MoO3 core/shell nanoparticles (NPs) doped poly(3,4-ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) hole-transporting layer (HTL). TiO2/MoO3 Core/shell NPs with size of approximately 40 nm are successfully prepared with a simple wet solution method and are interspersed into PEDOT: PSS layer to construct the HTL. The optimized device shows a high power conversion efficiency of 13.63%, which is dramatically improved compared with the reference device with a pristine PEDOT:PSS HTL. The improvement is mainly attributed to the increased crystalline of the CH3NH3PbI3-xClx film with large-scale domains and a compact morphology. More interesting, the cells exhibit superior stability in ambient conditions, which is attributed to the inhibited penetration of moisture due to the compact morphology of the CH3NH3PbI3-xClx film and the reduced hygroscopicity of the PEDOT:PSS film.

A solution processed MoO3/PEDOT:PSS bilayer structure is used as the hole transporting layer to improve the efficiency and stability of planar heterojunction perovskite solar cells. Increased hole extraction efficiency and restrained erosion of ITO by PEDOT:PSS are demonstrated in the optimized device due to the incorporation of an MoO3 layer.

High-performance panchromatic organic photodetectors (OPDs) containing small molecules lead phthalocyanine (PbPc) and C70 fullerene as donor and acceptor, respectively, were demonstrated. The OPDs had either a PbPc/C70 planar heterojunction (PHJ) or a PbPc/PbPc:C70/C70 hybrid planar-mixed molecular heterojunction (PM-HJ) structure. Both the PHJ and the PM-HJ devices showed a broad-band response that covered wavelengths from 300 to 1100 nm. An external quantum efficiency (EQE) higher than 10% and detectivity on the order of 1012 Jones were obtained in the wavelength region from 400 to 900 nm for the PHJ device. The EQE in the near-infrared region was enhanced by using the PM-HJ device structure, and a maximum EQE of 30.2% at 890 nm was observed for the optimized device with a 5% PbPc-doped C70 layer. Such an EQE is the highest at this wavelength of reported OPDs. The detectivity of the PM-HJ devices was also higher than that of the PHJ one, which is attributed to the increased efficiency of exciton dissociation in bulk heterojunction structure, increased absorption efficiency caused by formation of triclinic PbPc in the PbPc:C70 mixed film when it was deposited on a pristine PbPc layer, and high hole mobility of the PbPc-doped C70 layer.Keywords: bulk heterojunction; organic photodetector; panchromatic photoresponse; planar heterojunction; small molecule

•Inverted HTM-free planar heterojunction perovskite solar cells are constructed.•Devices are prepared by an all thermal evaporation process without thermal annealing.•A high PCE of 8.37% is obtained.•Superior stability is found for the devices for storage in ambient conditions.High efficiency and stable hole transporting material-free (HTM-free) planar heterojunction (PHJ) perovskite solar cells are constructed by directly thermal evaporating perovskite materials onto indium tin oxide substrate. A condense and homogeneous morphology is found for this perovskite film even without any annealing process. The optimized HTM-free CH3NH3PbI3−XClX/C60 PHJ device with a 35 nm ultra-thin CH3NH3PbI3−XClX layer presents a high hole extraction efficiency and a low charge carrier recombination probability, which results in a high short circuit current and fill factor. The HTM-free device shows a high power conversion efficiency of 8.37%, which is one of the highest efficiency among reported inverted HTM-free perovskite solar cells even that a thinner perovskite film is used. More importantly, the device also exhibits a superior stability in ambient conditions.

•We reported a low concentration donor OPV cell structure with an interlayer at anode.•The cell with a 5-nm SubPc interlayer had a peak PCE and a maximum Voc.•The improvement in PCE and Voc is mainly due to spectral built-in field at C60:TAPC BHJ induced by Schottky junction.We demonstrate organic photovoltaic (OPV) cells with structure of ITO/MoO3 (5 nm)/boron subphthalocyanine chloride (SubPc) (d nm)/C60:5 wt% 1,1-bis-(4-methyl-phenyl)-aminophenyl-cyclohexane (TAPC) (40 nm)/BCP (8 nm)/Al, where d = 0, 1, 3, 5, 7 and 13 nm. We found that a 5-nm-thick SubPc based cell had a peak power conversion efficiency (PCE) of 3.75% and a voltage (Voc) of 1.03 V, which was an increase of 35.4% and 0.19 V, respectively, compared with the reference cell without SubPc. We found that the spectral response of cells with 1–5 nm SubPc mostly corresponded to the C60 absorption and the cell with 5 nm SubPc had the highest responsivity. The spectral response of the cell with 13 nm SubPc corresponded to both C60 and SubPc absorptions, which is analogous to a previously reported flat heterojunction cell. The excellent PV parameter of the cell with 5 nm SubPc was attributed to a built-in field induced by the Schottky barrier contact of MoO3/5-nm SubPc. To confirm this hypothesis, another two series of OPV cells with different interlayers and donors instead of SubPc and TAPC were developed.

•EQE of 7.48% with single-emitting-layer fluorescent WOLED was achieved.•High efficiency was attributed to the up-conversion of TADF host triplet excitons.•Stable CIE coordinates shifted from (0.359, 0.439) to (0.358, 0.430) as the voltage increased from 5 V to 8 V.We demonstrated highly efficient and color stable single-emitting-layer fluorescent WOLEDs using blue thermally activated delayed fluorescent material of bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS) as host and traditional orange fluorescent material of (5,6,11,12)-tetraphenyl-naphthacene (rubrene) as dopant. At a low dopant concentration of 0.6 wt%, we achieved the efficient white emission that comprised of blue host and orange dopant. The maximum current efficiency, power efficiency and external quantum efficiency were 20.2 cd A−1, 15.9 lm W−1 and 7.48%, respectively. Besides, the Commission Internationale de I’Eclairage coordinates were almost the same with the increased voltage, which shifted from (0.359, 0.439) to (0.358, 0.430) as the voltage rose from 5 V to 8 V. The achievement of so high efficiency was attributed to the efficient up-conversion of DMAC-DPS triplet excitons and efficient energy transfer from host to dopant by Förster transfer mechanism. The more detailed working mechanism was also argued.

•A novel Ir–bt type complex with multi-fluorine functionalization was synthesized.•The complex exhibited high quantum yield (0.56) and short lifetime (0.37 μs).•Influence of fluorine atoms on photophysical properties of the complex was investigated.•Highly efficient yellow OLEDs using the complex as emitter were fabricated.•Stable yellow electrophosphorescence from the device was achieved.The performance of a heteroleptic bis-cyclometalated iridium complex based on 2-(2,3,4-trifluorophenyl)benzo[d]thiazole [(tfbt)2Ir(acac)] was investigated as a new phosphorescent emitter in OLEDs. The devices showed very high efficiency at various dopant concentrations and maximum efficiency was achieved at 6 wt% dopant concentration. A comparison of the performances of phosphorescent OLEDs with the new emitter versus those with prototype-based (bt)2Ir(acac) emitter revealed a remarkable improvement of efficiency at all dopant concentrations. These preliminary results obtained with the tfbt-based emitter indicate that this family of cyclometalated ligands with multi-fluorine functionalization is a promising compound for the development of highly emissive complexes.

•Highly efficient tandem cell with PCE of 7.66% was demonstrated.•Tandem cell consisted of two same SubPc:C70 bulk heterojunction subcells.•Improved performance was found by introducing thin F16CuPc in ICL.Highly efficient organic tandem solar cell with peak power conversion efficiency (PCE) of 7.66% has been demonstrated by simply stacking two same boron subphthalocyanine (SubPc):C70 bulk heterojunction devices, with a high active inter-connecting layer composed of bathophenanthroline (Bphen)/Silver/hexadecafluoro-copper-phthalocyanine (F16CuPc)/MoO3. We find that F16CuPc plays an important role which extends the recombination zone, facilitates the extraction of hole and the carrier recombination. The measured PCE of the tandem solar cell corresponds to a 38% increase compared to that the optimal single cell.

•Small molecule near-infrared photodetectors (NIR-PDs) based on a PbPc/C60 planar heterojunction are demonstrated.•The NIR-PDs show a broad-band response that extends to 1100 nm.•The optimized NIR-PD exhibits an EQE of 19.7% at 900 nm and a detectivity of 2.34 × 1011 Jones at zero bias.•The performance is higher than other small molecule NIR-PDs reported.High efficiency organic small molecule near-infrared photodetectors (NIR-PDs) based on a lead phthalocyanine/C60 planar heterojunction are demonstrated. The NIR-PDs show a broad-band response that extends to 1100 nm. The performance of the NIR-PDs is improved by using CuI as anode buffer layer. The optimized NIR-PD exhibits a response peak at about 900 nm with external quantum efficiencies (EQEs) of 19.7% at zero bias and 35.1% at −6 V, which are higher than other small molecule NIR-PDs reported. Comparable EQEs of 18.0% at zero bias and 33.2% at −6 V are found in the NIR-PD by further using 4,7-diphenyl-1,10-phenanthroline as cathode buffer layer. Meanwhile, the dark current is significantly reduced, which results in a high detectivity of 2.34 × 1011 Jones at zero bias, which is among the highest detectivities reported for organic small-molecule NIR-PDs. Besides, the NIR-PDs show a reliable stability in ambient condition.Graphical abstract

High-efficiency surface plasmon enhanced 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane:C70 small molecular bulk heterojunction organic solar cells with a MoO3 anode buffer layer have been demonstrated. The optimized device based on thermal evaporated Ag nanoparticles (NPs) shows a power conversion efficiency of 5.42%, which is 17% higher than the reference device. The improvement is attributed to both the enhanced conductivity and increased absorption due to the near-field enhancement of the localized surface plasmon resonance of Ag NPs.Keywords: localized surface plasmon resonance; metal nanoparticle; molybdenum trioxide; organic solar cell; small molecule;