Highly stable mixed-phase Cs-Cu-I films with tunable optoelectronic properties for UVB photodetector applications.

Ultraviolet (UV) photodetector plays an important role in military, civilian and people's daily life, and is an indispensable part of spectral detection. However, photodetectors target at the UVB region (280-320 nm) are rarely reported, and the devices detected by medium-wave UV light generally have problems such as low detection rate, low sensitivity, and poor stability, which are difficult to meet the market application needs. Herein, Cs-Cu-I films with mixed-phase have been prepared by vacuum thermal evaporation. By adjusting the proportion of evaporation sources (CsI and CuI), the optical bandgaps of mixed-phase Cs-Cu-I films can be tuned between 3.7 eV and 4.1 eV. This absorption cut-off edge is exactly at both ends of the UVB band, which indicating its potential application in the field of UVB detection. Finally, the photodetectors based on Cs-Cu-I/n-Si heterojunction are fabricated. The photodetector shows good spectral selectivity for UVB band, and has a photoresponsivity of 22 mA/W, a specific detectivity of 1.83*1011 Jones, an EQE over 8.7% and an on/off ratio above 20.

Homogenized NiOx nanoparticles for improved hole transport in inverted perovskite solar cells.

The power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) is still lagging behind that of conventional PSCs, in part because of inefficient carrier transport and poor morphology of hole transport layers (HTLs). We optimized self-assembly of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) onto nickel oxide (NiOx) nanoparticles as an HTL through treatment with hydrogen peroxide, which created a more uniform dispersion of nanoparticles with high conductivity attributed to the formation of Ni3+ as well as surface hydroxyl groups for bonding. A 25.2% certified PCE for a mask size of 0.074 square centimeters was obtained. This device maintained 85.4% of the initial PCE after 1000 hours of stabilized power output operation under 1 sun light irradiation at about 50°C and 85.1% of the initial PCE after 500 hours of accelerated aging at 85°C. We obtained a PCE of 21.0% for a minimodule with an aperture area of 14.65 square centimeters.

Inactive (PbI2)2RbCl stabilizes perovskite films for efficient solar cells.

In halide perovskite solar cells the formation of secondary-phase excess lead iodide (PbI2) has some positive effects on power conversion efficiency (PCE) but can be detrimental to device stability and lead to large hysteresis effects in voltage sweeps. We converted PbI2 into an inactive (PbI2)2RbCl compound by RbCl doping, which effectively stabilizes the perovskite phase. We obtained a certified PCE of 25.6% for FAPbI3 (FA, formamidinium) perovskite solar cells on the basis of this strategy. Devices retained 96% of their original PCE values after 1000 hours of shelf storage and 80% after 500 hours of thermal stability testing at 85°C.

Tunable morphology and highly stable α-CsPbI3 Nano-bricks for photoelectric devices.

CsPbI3 with suitable bandgap (∼1.73 eV) and excellent photoelectric performance are considered promising candidates for new-generation photovoltaic and photoelectric devices. However, the phase instability of CsPbI3 hinders its application in photoelectric devices. In this study, cubic phase CsPbI3 nano-bricks with high stability are prepared on Si substrates by catalyst-freehigh-pressure pulsedlaser deposition.Theeffectsofthetarget-substrate distance on the morphological, structural and photoluminescence propertiesofCsPbI3 nano-bricks are investigated. CsPbI3 nano-bricks exhibits excellent long-term stability for 12 months, which can be attributed to the smaller lattice mismatch between Si (100) and CsPbI3 (100). Furthermore, the photodetector based on CsPbI3/n-Si heterojunction exhibited obvious spectral response in the red band of 710 nm. This work provides a novel idea for the preparation of photoelectric devices with cubic CsPbI3.

Broadband Photodetector Based on Inorganic Perovskite CsPbBr3 /GeSn Heterojunction.

Photodetectors with broadband response spectrum have attracted great interest in many application areas such as imaging, gas sensing, and night vision. Here, a high performance broadband photodetector is demonstrated with inorganic perovskite CsPbBr3 /GeSn heterojunction, detection range can be covered from 450 to 2200 nm. The responsivity of heterojunction device can achieve as high as 129 mA W-1 under illuminated light of 532 nm, which is 4.92 times larger than that of a GeSn based device. As the CsPbBr3 can also act as anti-reflective coating for infrared wavelength, the infrared band responsivity at wavelength of 2200 nm can also be raised by 1.42 times. In addition, the device with all inorganic components is showed good stability, while keeping in the dry environment, the device can sustain its 90% original after 550 h storage. These results show the inorganic perovskite/GeSn heterojunction device is of great potential in broadband photodetection with high responsivity.

Growth and optoelectronic application of CsPbBr3 thin films deposited by pulsed-laser deposition.

All-inorganic perovskite CsPbBr3 thin films have been prepared on Si (100) substrate by a pulsed-laser deposition (PLD) technique, and the morphology, structure, absorbance, and photoluminescence properties of CsPbBr3 thin films are investigated. A photodetector based on CsPbBr3/n-Si heterojunction has been fabricated, and the performances of the device are characterized. The heterojunction photodetector exhibits diode-like rectifying behavior, and the photocurrent-to-dark-current ratio and peak responsivity of the heterojunction are approximately 168.5 and 0.6 A/W (-5 V, 520 nm), respectively. Furthermore, the CsPbBr3/n-Si heterojunction photodetector exhibits fast response and recovery times. With good optoelectronic properties, CsPbBr3 thin films prepared by PLD should be widely applicable to high-performance photodetectors and other optoelectronic devices.

Fast responsive and highly efficient optical upconverter based on phosphorescent OLED.

In this work, an organic-inorganic hybrid optical upconverter that can convert irradiated 980 nm IR light to 510 nm green phosphorescence sensitively was fabricated and studied. fac-Tris(2-phenylpyridine) iridium (Ir(ppy)3) doped 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) was used as emitting layer in the phosphorescent organic light-emitting diode (OLED) unit. The upconverter using a phosphorescent OLED as display unit can achieve a higher upconversion efficiency and a low power consumption when compared with the one using fluorescent. An upconversion efficiency of 4.8% can be achieved for phosphorescent device at 15 V, much higher than that of fluorescent one (2.0%). The upconverter's transient optical and electric response to IR pulse were also investigated for the first time. The response time was found to be influenced by IR intensity and applied voltage. It has a response time as short as 60 µs. The rapid response property of the upconverter makes it feasible to be applied to high-speed IR imaging systems.

Improved efficiency of organic/inorganic hybrid near-infrared light upconverter by device optimization.

An organic/inorganic hybrid up-conversion device was demonstrated in this work, which can convert near-infrared light (NIR) to visible green at high conversion efficiency. The upconverter was fabricated by integrating an In(0.12)Ga(0.88)As/GaAs multiquantum wells (MQWs) photodetector (PD) with an organic light emitting diode (OLED). The up-conversion efficiency of 4.0 W/W % was obtained at 20 V under NIR illumination of 1 mW/mm(2) at room temperature by optimizing the structure of the PD unit and adding MoO(3) doped perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as interfacial layer of OLED. Meanwhile, the green light output induced by NIR achieved 6050 cd/m(2), which proves that the organic/inorganic hybrid upconverter an excellent candidate that can be applied in light converter field.