This paper investigates the mechanism of light-soaking effects in inverted organic photovoltaic devices with zinc oxide and aluminum doped ZnO electron transport layers, which is important for development of low-cost and stable solar cells.

With a new polycarbonate-film-based dry transfer method, we successfully fabricated twisted stacked black phosphorus. Optical characterization showed the overlapping area had special optical response, and high-frequency Raman spectroscopy showed unexpected blue shifts in Ag 1 and Ag 2 modes. Density functional theory (DFT) calculations confirmed these blue shifts in twisted bilayer black phosphorus, and revealed significant interlayer coupling effects. Charge distribution calculations indicated other interactions beyond van der Waals force may exist in twisted bilayer black phosphorus. This finding may cast some insight on phonon modulation effect and give some potential applications such as optical filters and infrared photodetectors.

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A new solid solution system, Pb(Mg (1-x/2) Mn (x/2) W 1/2 )O 3 , is formed by replacing Mg 2+ with Mn 2+ in the Pb(Mg 1/2 W 1/2 ) O 3 complex perovskite. The solid solution remains in the orthorhombic Pmcn symmetry up to x = 0.1. It is observed that for such a chemical modification, the surface of the grain changes significantly. A stepped surface nanostructure appears in the Mn-substituted perovskite. Detailed surface morphology of the stepped patterns was revealed by atomic force microscopy (AFM), which determined that the interlayer step height varies from 2.3 to 8.3 nm. Analyse by XRD, SEM, EDX, and AFM suggest that the nature of the stepped surface structure may be the result of etching rather than spiral growth or twodimensional nucleation as it was previously believed.

This work presents our latest results for conventional and inverted organic photovoltaic (OPV) devices based on polymers such as poly(3-hexylthiophene) (P3HT) and poly[N-9”-hepta-decanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole) (PCDTBT) blended with fullerene derivatives such as [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) and PC71BM. It is observed that by controlling the morphology of acceptor and donor domains in the BHJ photoactive films higher power conversion efficiency (PCE) and performance for OPV devices can be achieved, with the best efficiencies demonstrated for the P3HT:PC61BM and PCDTBT:PC71BM devices exceeding 4% and 7%, respectively. Here, the interplay between fabrication processes and the performance of the devices is investigated to achieve optimum PCE, short-circuit current and open-circuit voltage for the OPV devices. In addition to contact and BHJ films, a flexible solar cell requires a flexible transparent conductor (TC). We report our results for conductive electrospun nanofiber based TCs as replacements for the brittle indium tin oxide (ITO) used for solar cells on glass substrates. These novel nanofiber TC web and their associated flexible substrates act as new platforms for fabrication of low cost, flexible solar cells. Performance of the TC is compared to other novel TCs in terms of transparency, sheet resistance and flexibility. The performance of the nanofiber TC webs is manifested in OPV devices that employ these TCs as the transparent electrode and demonstrate comparable performance to the devices using ITO electrodes. This work demonstrates the significance of novel materials and deposition technologies for enabling efficient and stable OPV devices for roll-to-roll manufacturing on flexible substrates.

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