The manipulation of crystal orientation from the thermodynamic equilibrium states is desired in layered hybrid perovskite films to direct charge transport and enhance the perovskite devices performance. Here we report a templated growth mechanism of layered perovskites from 3D-like perovskites which can be a general design rule to align layered perovskites along the out-of-plane direction in films made by both spin-coating and scalable blading process. The method involves suppressing the nucleation of both layered and 3D perovskites inside the perovskite solution using additional ammonium halide salts, which forces the film formation starts from solution surface. The fast drying of solvent at liquid surface leaves 3D-like perovskites which surprisingly templates the growth of layered perovskites, enabled by the periodic corner-sharing octahedra networks on the surface of 3D-like perovskites. This discovery provides deep insights into the nucleation behavior of octahedra-array-based perovskite materials, representing a general strategy to manipulate the orientation of layered perovskites.

Highly efficient planar heterojunction (PHJ) perovskite solar cells (PSCs) with a structure of ITO/ PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al were fabricated by a low-temperature solution process. As employed silica-coated gold (Au@SiO 2 ) nanorods at the interface between the hole transport layer PEDOT:PSS and the active layer CH 3 NH 3 PbI 3 , the average power conversion efficiency (PCE) showed over 40% enhancement, of which the average PCE was improved from 10.9% for PHJ-PSCs without Au@SiO 2 to 15.6% for PHJ-PSCs with Au@SiO 2 , and the champion one up to 17.6% was achieved. Both experiment and simulation results proved that prominent efficiency enhancement comes from the localized surface plasmon resonance of Au@SiO 2 nanorods which could improve the incident light trapping as well as improve the transport and collection of charge carrier, resulting in the enhancement in device parameters. The results suggest that metal nanorods, e.g., Au@SiO 2 , could be employed to fabricate highefficiency and low-cost PHJ-PSCs.

Highly efficient and reproducible cesium (Cs) doped triple cation (Cs, methylammonium (MA) and formamidinium (FA)) lead trihalide perovskite planar heterojunction (PHJ) solar cells are fabricated via low-temperature process with a simple architecture of ITO/SnO 2 /Perovskite/Spiro-OMeTAD/ Ag, of which the power conversion efficiency (PCE) up to 20.51% with negligible hysteresis and a steady output PCE of 20.22% can be achieved. Cs-intercalation is useful for forming high-quality Cs-doped triple cation perovskite films with larger gains and band gap as compared with perovskite films without Cs doping, leading to impressively enhanced photoluminescence lifetime and open circuit voltage (V oc ). Meanwhile, incorporating Cs þ into perovskite structure can result in lower charge-extraction time and prolonged charge-recombination lifetime, which are advantageous to improve the device performance. More importantly, Cs-doped triple cation PHJ perovskite solar cells (PSCs) exhibit better stability. They could maintain about 80% original PCE even exposed to air environments (humidity %40%) for over 500 hr without any encapsulation, while similar ones without Csdoping only maintain about 60% original PCE. The research work demonstrates that triple or multiple cation mixture is an effective strategy for structuring highly-efficient and stable PHJ-PSCs via low-temperature process, which may accelerate the commercialization of PSCs fabricated via large-scale printing techniques.

Ultrasmall black phosphorus quantum dots (BPQDs) serve as the near-infrared light absorber and charge transfer layer in the photocathode of a bifacial n-type dye sensitized solar cell. Wideband light absorption and ≈20% enhancement in the light-to-electron efficiency are accomplished due to the fast carrier transfer and complementary light absorption by the BPQDs demonstrating that BP has large potential in photovoltaics.

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