Enhanced performance of an inverted‐type polymer solar cell is reported by controlling the surface energy of a zinc oxide (ZnO) buffer layer, on which a photoactive layer composed of a polymer:fullerene‐derivative bulk heterojunction is formed. With the approach based on a mixed self‐assembled monolayer, the surface energy of the ZnO buffer layer can be controlled between 40 mN m−1 and 70 mN m−1 with negligible changes in its work function. For the given range of surface energy the power conversion efficiency increases from 3.27% to 3.70% through enhanced photocurrents. The optimized morphology obtained by surface energy control results in the enhanced photocurrent and transmission electron microscopy analysis verifies the correlation between the surface energy and the phase morphology of the bulk heterojunction. These results demonstrate that surface energy control is an effective method for further improving the performance of polymer solar cells, with potentially important implications for other organic devices containing an interface between a blended organic active layer and a buffer or an electrode layer.

Green-sensitive organic photodetectors (OPDs) with high sensitivity and spectral selectivity using boron subphthalocyanine chloride (SubPc) derivatives are reported. The OPDs composed of SubPc and dicyanovinyl terthiophene derivative (DCV3T) demonstrated the highest green-sensitivity with maximum external quantum efficiency (EQE) of 62.6 % at an applied voltage of -5 V, but wide full-width-at-half-maximum (FWHM) of 211 nm. The optimized performance considering spectral selectivity was achieved from the composition of N,N-dimethyl quinacridone (DMQA) and SubPc showing the high specific detectivity (D*) of 2.34 × 10(12) cm Hz(1/2)/W, the EQE value of 60.1% at -5 V, and narrow FWHM of 131 nm. In spite of the sharp absorption property of SubPc with the maximum wavelength (λmax) at 586 nm, the EQE spectrum showed favorable green-sensitivity characterized by smooth waveform with λmax at 560 nm, which is induced from the high reflectance of SubPc centered at 605 nm. The photoresponsivity of the OPD devices was found to be consistent with their absorptance. Optimized DMQA/SubPc device showed the lowest value of blue crosstalk (0.42) and moderate red crosstalk (0.37), suggesting its promising application as a green-sensitive OPD.

There are growing opportunities and demands for image sensors that produce higher-resolution images, even in low-light conditions. Increasing the light input areas through 3D architecture within the same pixel size can be an effective solution to address this issue. Organic photodiodes (OPDs) that possess wavelength selectivity can allow for advancements in this regard. Here, we report on novel push-pull D-π-A dyes specially designed for Gaussian-shaped, narrow-band absorption and the high photoelectric conversion. These p-type organic dyes work both as a color filter and as a source of photocurrents with linear and fast light responses, high sensitivity, and excellent stability, when combined with C60 to form bulk heterojunctions (BHJs). The effectiveness of the OPD composed of the active color filter was demonstrated by obtaining a full-color image using a camera that contained an organic/Si hybrid complementary metal-oxide-semiconductor (CMOS) color image sensor.

The precise control of morphology and orientation of block copolymers (BCPs) in thin films is crucial to fully exploit the potential of these materials for applications in nanotechnology such as nanolithographic templates for nanodevices, [1][2][3][4][5][6][7][8][9] nanoparticle patterning [10][11][12][13] and biological applications.[14]The control of block copolymer morphology is easily achieved by varying the molecular weight and the volume fraction of each block. The control of the orientation of block copolymer thin films is far more challenging as the BCP nanodomains spontaneously self-assemble into the configuration that minimizes the total free energy of the system. A block with a lower interfacial tension with a substrate preferentially wets the substrate whereas a block with a lower surface energy tends to locate at the surface exposed to air. These energetic fields exerted by the substrate and the free surface are strong enough to induce the parallel orientation of nanodomains. In order to establish the perpendicular orientation of a BCP film, which would lead to higher potentials for practical applications, the first approach would be to apply a perpendicular external or internal field that overcomes the surface fields. Electrical field [15][16][17] and solvent evaporation field [18][19][20][21] have been successfully introduced and critically tested. Another method consists of minimizing the difference in interfacial tensions between each block and the substrate by adjusting the surface energy of the substrate. [22][23][24][25][26][27][28] This surface state is referred to as the substrate neutrality, which has been achieved by the deposition of self-assembled monolayers [24][25][26] or copolymer brushes on the substrate. [20][21][22][23] In this case, the BCP film adopts the perpendicular orientation from the bottom interface or substrate toward the surface exposed to air. For thicker BCP films, the perpendicular orientation can not propagate all the way to the upper part of the film, and the final morphology is mixed, consisting of perpendicularly oriented domains at the bottom and parallel oriented domains in the upper part of the film. [23,[28][29][30] In this communication, we report on a new approach to induce the perpendicular orientation from the top of BCP films toward the bottom substrate. Our concept is based on the basic properties of surfactants that naturally locate at any interfaces to tailor the surface properties of a material. We demonstrate that the addition of a low molecular weight surfactant, oleic acid (hereafter denoted as OA), in present case can easily create the energetically neutral conditions at the top of the polystyrene-block-poly(methylmethacylate) (PS-b-PMMA) diblock copolymer thin films, resulting in the desired perpendicular orientation. Figure 1 demonstrates the remarkable efficiency of OA to induce the perpendicular orientation of BCP films. Figure 1a corresponds to the reference atomic force microscopy (AFM) height image of a 52k-52k lamellae structured PS-b-PMMA...