Owing to their ease of fabrication, low cost, and high flexibility, organic materials have attracted great interests in photodetector (PD) applications. However, suffering from large dark current, small photocurrent, low on–off ratio, and low sensitivity, performances of bare organic‐based PDs are not satisfactory. Integrating organic materials with other novel semiconductor materials offers an opportunity to overcome these drawbacks. Here, a lateral hybrid organic/lead sulfide (PbS) quantum dot bilayer PD is designed and fabricated, which significantly suppresses the dark current and enhances the photocurrent, leading to improved light detecting capability. Meanwhile, the bilayer PD can be made on a flexible polyimide substrate.

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We study the role of the dimer structure of light-harvesting complex II (LH2) in excitation transfer from the LH2 [without a reaction center (RC)] to the LH1 (surrounding the RC) or from the LH2 to another LH2. The excited and unexcited states of a bacteriochlorophyll (BChl) are modeled by a quasispin. In the framework of quantum open system theory, we represent the excitation transfer as the total leakage of the LH2 system and then calculate the transfer efficiency and average transfer time. For different initial states with various quantum superposition properties, we study how the dimerization of the B850 BChl ring can enhance the transfer efficiency and shorten the average transfer time.

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long carrier diffusion lengths, [9,10] and low deep-state defects. [11,12] Owing to their exciting photovoltaic applications, their promising potential in photodetection is drawing growing interest. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Yang and co-workers first fabricated a vertical perovskite photodetector, [13] which demonstrated excellent light detecting capability. Lateral photodetectors are easy to make, and more importantly, their intrinsic gain mechanism can lead to very high photosensitivity. [30] Thereby many efforts have been devoted to developing such lateral devices. For single-layer perovskite devices reported, [14][15][16][17] relatively high detectivity (≈10 12 Jones) and short rise/decay time (dozens of milliseconds) were realized, but this is always associated with low on/ off ratios and poor electrical instabilities (induced by ion migration). To meet such challenge, bilayer devices are designed: perovskite film responsible for light absorption and another material film responsible for carriers transport. Significant enhancement in photoresponsivity has been achieved. [18][19][20][21][22][23][24] However, the reported bilayer devices usually employed high-conductive 2D layer to function as main photocarrier transport channel, and this leads to certain detrimental defects. For example, the graphene/perovskite bilayer devices exhibit very low on/off ratio of smaller than 2, [18][19][20][21] and the transition metal sulfides (WS 2 , MoS 2 )/perovskite bilayer devices have very long rise/decay time of a few seconds. [22,23] Also, it should be noted that graphene and the transition metal sulfides are usually deposited by complex and costly process, such as chemical vapor deposition, mechanical exfoliation, and hence is not suitable for large-area fabrication. Solutionprocessed MoS 2 [24] or organic [25,26] /CH 3 CH 3 PbI 3 photodetectors have been fabricated, but their performances are still limited by low on/off ratios of <500. Here we employed TiO 2 nanocrystal (NC) film to transport photocarrier. The designed TiO 2 NC/perovskite bilayer photodetector exhibits high overall performance with on/off ratio of 4000, photodetectivity of 1.85 × 10 12 Jones, and rise/decay time of 0.49/0.56 s. Figure 1a presents the schematic structure of the TiO 2 NC/ perovskite bilayer photodetector fabricated on a glass substrate. First, the TiO 2 NC film was spin coated on the glass substrate, and then Al electrodes were thermally evaporated on the TiO 2 NC film with help of an interdigital mask, resulting in a channel length of 80 µm and a channel width of 8800 µm. The perovskite film (CH 3 NH 3 PbI 3 ) was then spin coated on the TiO 2 NC film, completing the device fabrication (details Owing to their attractive performance in photovoltaic devices, organolead halide perovskite materials have attracted enormous interest for photodetector applications. However, current perovskite-based photodetectors mainly rely on high-conductive 2D materials such as graphene or transition metal sulfi...

A new family of functionalized second-order nonlinear optical polyimides has been developed. The key step in synthesizing these polymers was the syntheses of diamino NLO chromophores, which was accomplished by utilizing the Mitsunobu reaction. The polyimides were obtained from the corresponding poly(amic acids) which exhibited good solubility in aprotic polar solvents, permitting device processing. High glass transition temperatures were obtained in these polyimides, rendering a high stability in dipole orientation at elevated temperatures. The second harmonic generation signals exhibited no decay at room temperature or at 90 °C. A long term stability at 170-180 °C was observed.