The rapid growth of organic–inorganic hybrid perovskite materials (such as methylammonium lead triiodide, MAPbI3) in photoelectric applications has prompted investigations of novel strategies to improve photodetection performance. Although a few surface nanofabrication methods have been applied to texture perovskite thin films to enhance light trapping, it remains challenging to pattern large-area periodic perovskite nanoarrays in a tunable and scalable manner. In this work, we report a facile and low-cost approach to fabricate large-area SiO2/Si nanopyramids arrays through nanosphere lithography. These nanopyramids arrays are used to pattern MAPbI3 thin films. We find that the introduction of nanopyramid arrays enhances the light intensity within the perovskite film, which is confirmed by light absorption tests and optical simulations. As a result, the photodetectors based on MAPbI3 with nanopyramid structures show excellent responsivity of 28.8 ± 1.0 A/W and detectivity of (3.5 ± 0.1) × 1011 Jones at 650 nm. The photoresponse of the photodetector to pulsed light is highly stable and reproducible, with rise and decay times of ∼0.7 and 1.1 ms, respectively. They also have a broader light sensitivity range from ultraviolet to infrared light, i.e., 340 nm to 1100 nm, compared to those without nanostructures. Finally, we demonstrate a prototype image sensor using these photodetector arrays.

Spectrally selective narrowband photodetection is critical for near‐infrared (NIR) imaging applications, such as for communicationand night‐vision utilities. It is a long‐standing challenge for detectors based on silicon, to achieve narrowband photodetection without integrating any optical filters. Here, this work demonstrates a NIR nanograting Si/organic (PBDBT‐DTBT:BTP‐4F) heterojunction photodetector (PD), which for the first time obtains the full‐width‐at‐half‐maximum (FWHM) of only 26 nm and fast response of 74 µs at 895 nm. The response peak can be successfully tailored from 895 to 977 nm. The sharp and narrow response NIR peak is inherently attributed to the coherent overlapping between the NIR transmission spectrum of organic layer and diffraction enhanced absorption peak of patterned nanograting Si substrates. The finite difference time domain (FDTD) physics calculation confirms the resonant enhancement peaks, which is well consistent with the experiment results. Meanwhile, the relative characterization indicates that the introduction of the organic film can promote carrier transfer and charge collection, facilitating efficient photocurrent generation. This new device design strategy opens up a new window in developing low‐cost sensitive NIR narrowband detection.

Seismic anisotropy exists in various type of strata and should be considered in seismic imaging schemes. Seismic imaging algorithms based on isotropic assumption neglect the impacts of anisotropy on seismic data, which causes migration artifact and waveform distortion. To correct the effects of anisotropy on seismic wave propagation, we propose an imaging algorithm that performs least-squares reverse time migration in vertical transversely isotropic acoustic media. We derive the following operators to implement this algorithm, the de-migration operator, its adjoint migration operator and the corresponding gradient. However, an inaccurate estimated source wavelet will introduce the error in the seismic simulation, and thus increase the mismatch between observed and synthetic data for least-squares reverse time migration. In addition, the noises, especially the noises with abnormal amplitudes in the seismic data, damage the inversion convergence and reduce the imaging resolution. To improve the image quality, we propose to use convolved wavefields between observed and synthetic data so that such mismatch can be independent of the source wavelets. Also, we employ the student's t-distribution instead of L2 norm in our inversion scheme to better handle the seismic noise. Its implementation only modifies the gradient of the conventional least square reverse time migration scheme. Our numerical tests show a clear improvement using our proposed imaging algorithm when compared with the conventional isotropic migration scheme for the anisotropic data. Also, the synthetic examples demonstrate the feasibility and effectiveness of our proposed source-independent algorithm using the student's t-distribution.