In recent years, taking advantages of high light absorption coefficients, long charge carrier diffusion lengths and intense photoluminescence, halide perovskites have attracted a great deal of interest in developing high-performance optoelectronic devices including solar cells, light-emitting diodes, photodetectors, transistors, lasers, and so on. Especially, the excellent combination of effective light absorption with tailorable absorption spectrum and high charge carrier mobility in a broadband range makes perovskite-based photodetectors different from traditional photodetectors made of inorganic semiconductors such as GaN, Si, and InGaAs. According to the recent reports, perovskites are promising to greatly improve responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed of photodetectors. Here, we summarize the recent advancements in organic-inorganic hybrid perovskite-based photodetectors in terms of the progress in various low-dimension perovskites, and the recent effective approaches to enhance the performance of perovskite photodetector based on the interfacial engineering in perovskite heterostructures. Besides, two kinds of perovskite photodetectors, namely vertical structure and lateral structure, are analyzed, and the challenges to achieve practical applications in photodetectors are also discussed.

High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

Perovskite light-emitting diodes (PeLEDs) employing CH3NH3PbBr3 as the emission layer (EML) and graphene oxide (GO) doped PEDOT:PSS as the hole transport layer (HTL) were prepared and characterized.

High efficiency perovskite light-emitting diodes (PeLEDs) using PEDOT:PSS/MoO3-ammonia composite hole transport layers (HTLs) with different MoO3-ammonia ratios were prepared and characterized. For PeLEDs with one-step spin-coated CH3NH3PbBr3 emitter, an optimal MoO3-ammonia volume ratio (0.02) in PEDOT:PSS/MoO3-ammonia composite HTL presented a maximum luminance of 1082 cd/m2 and maximum current efficiency of 0.7 cd/A, which are 82% and 94% higher than those of the control device using pure PEDOT:PSS HTL respectively. It can be explained by that the optimized amount of MoO3-ammonia in the composite HTLs cannot only facilitate hole injection into CH3NH3PbBr3 through reducing the contact barrier, but also suppress the exciton quenching at the HTL/CH3NH3PbBr3 interface. Three-step spin coating method was further used to obtain uniform and dense CH3NH3PbBr3 films, which lead to a maximum luminance of 5044 cd/m2 and maximum current efficiency of 3.12 cd/A, showing enhancement of 750% and 767% compared with the control device respectively. The significantly improved efficiency of PeLEDs using three-step spin-coated CH3NH3PbBr3 film and an optimum PEDOT:PSS/MoO3-ammonia composite HTL can be explained by the enhanced carrier recombination through better hole injection and film morphology optimization, as well as the reduced exciton quenching at HTL/CH3NH3PbBr3 interface. These results present a promising strategy for the device engineering of high efficiency PeLEDs.

Organic light-emitting diodes (OLEDs) have drawn a great deal of attention due to their broad applications in lighting and displaying. With the development of nanotechnology, surface plasmas have been widely used in photonics, microscopes, solar cells and biosensors. In this paper, by inserting graphene oxide (GO), Au nanoparticles (Au NPs) and GO/Au NP composite structures between the hole transport layer (NPB) and indium tin oxide (ITO) anode, respectively, the electroluminescent performance of Alq 3-based OLEDs was significantly enhanced. Compared to the reference devices, the devices with the composite inserting layer containing 10% GO/Au NP doping have the best electroluminescent performance, which improved 47.9% in maximum luminance, 49.2% in maximum current efficiency and 45.3% in maximum external quantum efficiency (EQE). Such substantial enhancement of photoelectric performance can be attributed to the combined effects of LSPR coupling and the better hole transport property by introducing Au NPs and a graphene oxide-doped layer.