Top illuminated organic photodetectors with dielectric/metal/dielectric transparent anode

The top illuminated organic photodetectors (OPDs) with a Dielectric/Metal/Dielectric (DMD) transparent anode are fabricated. The transparent electrode is composed of molybdenum trioxide (MoO₃)/silver (Ag)/MoO₃ layers and zinc oxide (ZnO)/aluminum (Al) is used for bottom cathode. The optimized DMD electrode has an optical transmittance of 85.7% at the wavelength of 546 nm and sheet resistance of ∼6 Ω/sq. The fabricated OPDs exhibit a high detectivity and wide range linearity.     

弱光位敏探测器

提出卫种新型弱光位敏探测器，总结了该器件理论分析设计，给出了实验结果，并与传统光电倍增管比较了优缺点。     

Bandwidth and transient analysis of bilayer organic photodetectors

Utilization of organic photodetectors (OPDs) and their applications for assembling on flexible and curved substrates have increased in recent years. However, organic semiconductors suffer from low carrier mobility that demands an optimized design and precise modeling for their applications. The OPDs frequency bandwidth is one of the most important criteria that needs to be investigated carefully. In this paper a comprehensive physical time-domain framework is introduced for bandwidth calculations as well as other several evaluation criteria. This model is verified by experimental measurements. According to the results, increasing the reverse bias voltage boosts the bandwidth of OPD owing to the increase of the carrier mobility. Based on the introduced simulation approach, the trade-off between the bandwidth and the responsivity has been investigated and an efficient design method is also proposed which could effectively improve the OPD performance.     

10.6μm CO2激光对HgCdTe探测器破坏阈值的实验研究

用10．6μm脉冲CO2激光辐照PC型HgCdTe光电探测器进行破坏阈值实验研究,通过政变激光辐照到探测器上的能量密度直至探测器损伤、破坏,得出了HgCdTe探测器的破坏阈值;利用一维半无限大模型计算了激光损伤探测器的破坏阈值,并与实验值进行了比较。分析表明,实验误差不仅来自于探测器不同的材料性质,而且与光斑的大小,探测器的制作工艺等多种因素有关;分析了不同脉宽的激光脉冲对破坏阈值的影响,得出了合理的破坏阈值。     

High efficient UV-A photodetectors based on monodispersed ligand-capped TiO2 nanocrystals and polyfluorene hybrids

Monodispersed ligand-capped TiO₂ nanocrystals are synthesized by a low temperature solvothermal method using oleic acid (OA) as the capping agent. The single layer hybrid films based on the OA-capped TiO₂ nanocrystals and poly(9,9-dihexylfluorene) (PFH) are prepared by solution processing at room temperature and characterized by atomic force microscopy, UV-vis absorption and photoluminescence spectra. The hybrid film is applied in the fabrication of nanostructured UV-A photodetector (320-420 nm) by sandwiching it between two electrodes to form bulk heterojunction. The high ultraviolet signal-to-noise ratio of 3 orders of magnitude with short response time less than 200 ms can be achieved for the device. Furthermore, the device shows drastic changes in current under a wide range of UV irradiation with a linear relationship between them. The thermal behavior of the device is also discussed. The high photosensitivity in the UV-A range and the low-cost endow them with potential for environmental and biological uses.     

Photomultiplication in Disordered Unipolar Organic Materials

Photomultiplication in conventional inorganic semiconductors has been known and used for decades, the underlying mechanism being multiplication by impact ionization triggered by hot carriers. Since neither carrier heating by an electric field nor avalanche multiplication are possible in strongly disordered organic solids, charge multiplication seems to be highly unlikely in these materials. However, here the photomultiplication observed in the bulk of a unipolar disordered organic semiconductor is reported. The proportion of extracted carriers to incident photons is experimentally determined to be in excess of 3000 % in a single‐layer device of the air‐stable, n‐type organic semiconductor F₁₆CuPc (Pc: phthalocyanine). This effect is explained in terms of exciton quenching by localized charges, the subsequent promotion of these detrapped charges to the high‐mobility energy band of the density‐of‐states (DOS) distribution, and subsequent slow equilibration within this broad intrinsic DOS. Such a mechanism allows multiple replenishment of the optically released charge by mobile carriers injected from an Ohmic electrode. Also shown is photomultiplication in double‐layer devices composed of layers of donor and acceptor small‐molecule materials. This result implies that, apart from exciton dissociation at a donor/acceptor interface, exciton energy transfer to trapped carriers is a complementary photoconductivity process in organic solar cells. This new insight paves the way to cheap, highly efficient organic photodetectors on flexible substrates for numerous applications.     

SMA同轴封装高速光电探测器

采用自制ＳＭＡ同轴管壳和普通ＴＯ－１８管壳对同型同批的ＩｎＧａＡｓＰＩＮ光电探测器芯片进行了封装，并用自建测试系统对其Ｃ－Ｖ特性和瞬态特性进行了测试比较，结果表明：与普通ＴＯ－１８管壳封装相比，ＳＭＡ同轴管壳封装器件电容减少了约０．４ｐＦ，上升时间ｔｒ由８５ｐｓ减至２５ｐｓ以下，半高全宽ＦＷＨＭ由２１０ｐｓ减至８５ｐｓ，等效－３ｄＢ带宽增至６ＧＨｚ以上，瞬态特性显著改善。     

New Compenated Method to the Phase for a Bulk Optic Faraday Current Sensor

A new method to reduce the reflection-induced phase between the two ortho-gonal components of the linearly polarized light after the reflections is presented.This kind of sensor haad essier to fabricate and adjust than that whose internal reflection is at critical angle.     

Photoresponse Properties of CdSe Single‐Nanoribbon Photodetectors

Photodetectors are fabricated from individual single‐crystal CdSe nanoribbons, and the photoresponse properties of the devices are studied systematically. The photodetector shows a high sensitivity towards excitation wavelength with a sharp cut‐off at 710 nm, corresponding to the bandgap of CdSe. The device exhibits a high photo‐to‐dark current ratio of five orders of magnitude at 650 nm, and can function with excellent stability, reproducibility, and high response speed (< 1 ms) in a wide range of switching frequency (up to 300 Hz). The photocurrent of the device shows a power‐law dependence on light intensity. This finding together with the analysis of the light intensity‐dependent response speed reveals the existence of various traps at different energy levels (shallow and deep) in the bandgap. Coating with a thin SiO₂ isolating layer increases the photocurrent but decreases the response speed of the CdSe nanoribbon, which is attributed to reduction of recombination centers on ribbon surface.