Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.

Effective management of the insulating ligands is prerequisite for achieving good electrical coupling between colloidal quantum dots (CQDs) and, thus, highperformance solar cells. Here, we developed a rationally designed post-synthetic process for effective control of ligand density on organic-inorganic hybrid formamidinium lead triiodide (FAPbI 3) perovskite CQDs. The resulting FAPbI 3 CQD solar cells demonstrated power-conversion efficiency of 8.38% with stability superior to that of bulk FAPbI 3 devices.

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The creation of new organic-inorganic phototransistors with high and broad spectral photosensitivity is reported. The extended charge transport and photoconductivity between the layers in the bilayer structure results in a notable detectivity of over 10(12) Jones and a linear dynamic range of over 100 dB at a broad spectral bandwidth across the UV-NIR range. Furthermore, the considerably reduced persistent photocurrent effect of In-Ga-Zn-O (IGZO)-based hybrid phototransistors is first demonstrated via an organic-inorganic bilayer approach.

Van der Waals growth of GaAs on silicon using a two‐dimensional layered material, graphene, as a lattice mismatch/thermal expansion coefficient mismatch relieving buffer layer is presented. Two‐dimensional growth of GaAs thin films on graphene is a potential route towards heteroepitaxial integration of GaAs on silicon in the developing field of silicon photonics. Hetero‐layered GaAs is deposited by molecular beam epitaxy on graphene/silicon at growth temperatures ranging from 350 °C to 600 °C under a constant arsenic flux. Samples are characterized by plan‐view scanning electron microscopy, atomic force microscopy, Raman microscopy, and X‐ray diffraction. The low energy of the graphene surface and the GaAs/graphene interface is overcome through an optimized growth technique to obtain an atomically smooth low­ temperature GaAs nucleation layer. However, the low adsorption and migration energies of gallium and arsenic atoms on graphene result in cluster‐growth mode during crystallization of GaAs films at an elevated temperature. In this paper, we present the first example of an ultrasmooth morphology for GaAs films with a strong (111) oriented fiber‐texture on graphene/silicon using quasi van der Waals epitaxy, making it a remarkable step towards an eventual demonstration of the epitaxial growth of GaAs by this approach for heterogeneous integration.