The electronic structure and optical absorption spectra of polymer APFO₃, [70]PCBM/APFO₃ and [60]PCBM/APFO₃, were studied with density functional theory (DFT), and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT). Visualized charge difference density analysis can be used to label the charge density redistribution for individual fullerene and fullerene/polymer complexes. The results of current work indicate that there is a difference between [60]PCBM and [70]PCBM, and a new charge transfer process is observed. Meanwhile, for the fullerene/polymer complex, all calculations of the twenty excited states were analyzed to reveal all possible charge transfer processes in depth. We also estimated the electronic coupling matrix, reorganization and Gibbs free energy to further calculate the rates of the charge transfer and the recombination. Our results give a clear picture of the structure, absorption spectra, charge transfer (CT) process and its influencing factors, and provide a theoretical guideline for designing further photoactive layers of solar cells.

Plant recognition has great potential in forestry research and management. A new method combined back propagation neural network and radial basis function neural network to identify tree species using a few features and samples. The process was carried out in three steps: image pretreatment, feature extraction, and leaf recognition. In the image pretreatment processing, an image segmentation method based on hue, saturation and value color space and connected component labeling was presented, which can obtain the complete leaf image without veins and background. The BP-RBF hybrid neural network was used to test the influence of shape and texture on species recognition. The recognition accuracy of different classifiers was used to compare classification performance. The accuracy of the BP-RBF hybrid neural network using nine dimensional features was 96.2%, highest among all the classifiers.

Accurate identification of apple leaf diseases is of great significance for improving apple yield. The lesion area of the apple leaf disease image is small and vulnerable to background interference, which easily leads to low recognition accuracy. To solve this problem, a lightweight bilinear convolutional neural network (CNN) model named BLSENet based on attention mechanism is designed. The model consists of two subnetworks, and each subnetwork is embedded with a Squeeze-and-Excitation (SE) module. By using the feature extraction ability of the two subnetworks and combining the bilinear feature CONCAT operation, the multiscale features of the image are obtained. Compared with the unimproved model LeNet-5 (84.63%), BLSENet has higher accuracy in the test set, which indicates that SE module and bilinear feature fusion have a positive effect on the performance of the model, and BLSENet has the ability to identify apple leaf diseases. The model has achieved the expected goal and can provide technical support for accurate identification and real-time monitoring of apple disease images.

The ground state geometry, optical and charge transport properties of benzodifurandione-based PPV (BDPPV) have been studied with density functional theory methods. Firstly, the frontier molecular orbitals, energy gap (Δ_H–L), ionization potentials (IP) and electron affinities (EA), optical absorption spectra of BDPPV were obtained in the framework of DFT and TD-DFT. Reorganization energy and charge transfer integral were estimated to calculate the drift mobility. Thereafter, we further studied the effect of sulfur atoms substitution and external electric fields on the spectra response and charge transport properties. The calculated results showed that for BDPPV, the drift mobility of electrons is higher than that of the holes due to the strong charge coupling strength. The substitution of oxygen by sulfur atoms has a significant influence on the bond length, dihedral angle and the energy levels of the frontier molecular orbitals; at the same time, the absorption wavelengths can be effectively adjusted by controlling the numbers and sites of substituted sulfur atoms. When two pairs sulfur atoms were introduced (such as Su4), it exhibits a good optical response and improves the charge transport ability, suggesting that molecules with two pairs sulfur atoms substituted could be an optimal candidate for optic-electron materials.