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One major drawback that prevents the largescale practical implementation of perovskites is their susceptibility to performance degradation in humid environments. Here, we achieved uniform, stable perovskite films within a polyvinylpyrrolidone (PVP) polymer frame via mild solution processing in ambient air with over 60% relative humidity. In addition to facilitating film formation, the hydrophobic PVP served to protect the perovskite grains from atmospheric moisture. Use of PVP, coupled with optimization of the deposition parameters, provided for compact, smooth, pinhole-free perovskite films that when incorporated into a photovoltaic device exhibited highly reproducible efficiencies in the range of up to 17%. In the absence of encapsulation, the devices exhibited stable performance characteristics during exposure to humid ambient air for 600 h. Furthermore, on flexible substrates, the 8 wt % PVP−perovskite samples provided for device efficiencies of ca. 15%. The devices retained ca. 73% of their efficiency after bending 1000 times with a bending radius of 0.5 cm.

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Using a hydrophobic coating over a CH3NH3PbI3 absorbing layer can prevent perovskite solar cells from erosion due to humidity in the air.

TiO2 microspheres assembled by single crystalline rutile TiO2 nanorods were synthesized by one-pot solvothermal treatment at 180 °C based on an aqueous-organic mixture solution containing n-hexane, distilled water, titanium n-butoxide and hydrochloric acid. The spheres had a radiative structure from the center, and their diameters were controlled in the range from 1 to 5 μm by adjusting the volume of the reactant water. Nitrogen adsorption-desorption isotherms showed that all the as-prepared microspheres had relatively high specific surface areas of about 50 m(2) g(-1). The 1 μm sized TiO2 nanorod microspheres were fabricated as a scattering overlayer in DSSCs, leading to a remarkable improvement in the power conversion efficiency: 8.22% of the bi-layer DSSCs versus 7.00% for the reference cell made of a single-layer film prepared from nanocrystalline TiO2. Such improvement was mainly attributed to the enhanced light harvesting and dye loading brought by the effective scattering centers.

No abstract

Tin dioxide (SnO 2 ) has emerged as an effective electron transport layer (ETL) in perovskite solar cells because of its good chemical stability, low annealing temperature, and relatively high electron mobility. However, the defect sites derived from the lowtemperature solution process inevitably affect the device performance. Here, we report cesium carbonate (Cs 2 CO 3 ) as a modifier to improve the electronic property of the SnO 2 ETL and passivate the defects at the perovskite/SnO 2 interface. It is found that Cs 2 CO 3 modification could reduce the roughness and improve the surface wettability of the SnO 2 film, resulting in much larger perovskite grains. In addition, the Cs 2 CO 3 treatment leads to a lower film work function, which effectively accelerates the electron transfer and inhibits the carrier recombination. As a consequence, the low-temperature-processed Cs 2 CO 3treated SnO 2 enables a significantly enhanced power conversion efficiency of 19.5% in comparison with 15.6% of the pristine device. Moreover, the hysteresis of the devices is obviously suppressed because of the optimization of both perovskites and perovskite/SnO 2 interfaces.

CuInS2 quantum-dot sensitized TiO2 photoanodes with In2S3 buffer layer were in situ prepared via chemical bath deposition of In2S3, where the Cd-free In2S3 layer then reacted with TiO2/CuxS which employed a facile SILAR process to deposit CuxS quantum dots on TiO2 film, followed by a covering process with ZnS layer. Polysulfide electrolyte and Cu2S on FTO glass counter electrode were used to provide higher photovoltaic performance of the constructed devices. The characteristics of the quantum dots sensitized solar cells were studied in more detail by optical measurements, photocurrent-voltage performance measurements, and impedance spectroscopy. On the basis of optimal CuxS SILAR cycles, the best photovoltaic performance with power conversion efficiency (η) of 1.62% (Jsc = 6.49 mA cm(-2), Voc = 0.50 V, FF = 0.50) under full one-sun illumination was achieved by using Cu2S counter electrode. Cu2S-FTO electrode exhibits superior electrocatalytic ability for the polysulfide redox reactions relative to that of Pt-FTO electrode.