RESUMEN
In this work, the photovoltaic performance and stability of perovskite solar cells (PSCs) based on a dopant-free hole transport layer (HTL) are efficiently improved by inserting a two-dimensional (2D) interfacial layer. The benzyl ammonium lead iodide (BA2PbI4) 2D perovskite is used as an interfacial layer between the 3D CH3NH3PbI3 perovskite and two moisture-resistant dopant-free HTLs including poly[[2,3-bis(3-octyloxyphenyl)-5,8-quinoxalinediyl]-2,5-thiophenediyl] (TQ1) and poly(3-hexylthiophene) (P3HT). TQ1 with a facile synthesis procedure has a higher moisture resistivity compared to P3HT which can improve the stability of PSCs. The 2D BA2PbI4 perovskite with a less-volatile bulkier organic cation efficiently passivates the defects at the perovskite/HTL interface, leading to 11.95% and 15.04% efficiency for the modified TQ1 and P3HT based cells, respectively. For a better understanding, the structural, optical, and electrical properties of PSCs comprising P3HT and TQ1 HTLs with and without interface modification are studied. The interface modified PSCs show slower open-circuit voltage decay and longer carrier lifetimes compared to unmodified cells. In addition, impedance spectroscopy reveals lower charge transport resistance and higher recombination resistance for the modified devices, which could be associated with the modification of the interface between the 3D CH3NH3PbI3 perovskite and HTL caused by the 2D interfacial layer. Also after aging under ambient conditions for about 800 hours, the modified PCSs retain more than 80% of their initial PCEs. These results give us the hope of achieving simpler, cheaper, and more stable PSCs with dopant-free HTLs through 2D interfacial layers, which have great potential for commercialization.
RESUMEN
Two-dimensional (2D) transition metal dichalcogenides are promising candidates of photodetectors where they are commonly grown parallel to the substrate due to their 2D characteristics in micrometer scales from exfoliation of bulk crystals or through high temperature chemical vapor deposition (CVD) methods. In this study, semi-hexagonal vertical nanosheets of SnS2 layered have been fabricated on FTO substrate without using Sn source through CVD method at relatively low temperature (500 °C). Due to exceptional band alignment of triple cation lead perovskite (TCLP) with semi-hexagonal SnS2 nanosheets, an improved photodetector has been fabricated. This type of photodetectors fabricated through lithography-free and electrodes metallization free approach with remarkable fast response (20.7 µs/31.4 µs as rising /falling times), showed high photoresponsivity, external quantum efficiency and detectivity of 1.84 AW-1, 513% and 1.69 × 1011, respectively under illumination of incident light with wavelength of 445 nm. The stability of the photodetectors has been studied utilizing a protective PMMA layer on the perovskite layer in 100% humidity. The introduced growth and fabrication process of the planar photodetector, including one/two dimensional interface through the edges/basal planes of layered materials with perovskite film, paves a way for the large scale, cost-effective and high-performance optoelectronic devices.
RESUMEN
Antisolvent crystallization is known as an effective approach for the deposition of pinhole-free solution-processed perovskite layers for high-performance solar cells. Here, we introduce a modified antisolvent dripping method by adding tetra ethyl orthosilicate (TEOS) into chlorobenzene as a conventional antisolvent. Through TEOS modification, perovskite solar cells show efficiencies as high as 16% with more than 85% retention after 290 h storage at ambient conditions in comparison to 20% in pristine cells. This significant enhancement in efficiency and stability mainly related to the decrement of the density of surface defects, which is confirmed by considerably enhanced photoluminescence of perovskite layers. Also, electrochemical impedance spectroscopy results show lower charge recombination at interfaces in modified cells. Regarding the obtained results, our modified antisolvent approach is a simple and promising route to prepare high-quality perovskite layers for solar cell applications.
RESUMEN
Here we investigate the effect of seed layer deposition on electron-transport parameters of chemical-bath-deposited (CBD) CdSe quantum dot sensitized solar cells (QDSCs). Fill factors were systematically improved to more than 0.6 through reduced recombination after seed layer deposition. Considering the beneficial effects of seed layer deposition, noticeably higher efficiency values were systematically obtained in cells with the seed layer (2-3.19%) in comparison to cells without a seed layer (0.03-0.46%) depending on the TiO2 photoanode particle size. Electron-transport parameters in cells, including chemical capacitance, recombination resistance, the diffusion coefficient, electron life time and small perturbation diffusion lengths of electrons were examined by modeling the experimental impedance spectroscopy data. We showed that a seed layer enhanced recombination resistance in cells, while the photoanode conduction band position was not affected. Higher diffusion lengths of electrons were obtained after seed layer deposition, correlated to the reduced electron recombination rate by redox electrolyte through seed layer deposition. As a general conclusion we report that while the seed layer generally is deposited to increase light absorption, at the same time this could be applied in order to systematically enhance charge-transport properties in cells and it has a clear application in the optimization of QDSC performance.
RESUMEN
TiO(2) hollow fibers with high surface area were manufactured by a simple synthesis method, using natural cellulose fibers as template. The effective light scattering properties of the hollow fibers, originating from their micron size, were observed by diffuse reflectance spectroscopy. In spite of the micrometric length of the TiO(2) hollow fibers, the walls were highly porous and high surface area (78.2 m(2) g(-1)) was obtained by the BET method. TiO(2) hollow fibers alone and mixed with other TiO(2) pastes were sensitized with CdSe quantum dots (QDs) by Successive Ionic Layer Adsorption and Reaction (SILAR) and integrated as a photoanode in quantum dot sensitized solar cells (QDSCs). High power conversion efficiency was obtained, 3.24% (V(oc) = 503 mV, J(sc) = 11.92 mA cm(-2), FF = 0.54), and a clear correspondence of the cell performance with the photoanode structure was observed. The unique properties of these fibers: high surface area, effective light scattering, hollow structure to facile electrolyte diffusion and the rather high efficiencies obtained here suggest that hollow fibers can be introduced as promising nanostructures to make highly efficient quantum dot sensitized solar cells.