Yafeng Deng,Zhanhong Ma,Fengzhang Ren,Guangxin Wang
An innovative two-step method perfectly prepared TCLs with different thicknesses, and then the TNA films based on TCLs were successfully prepared. The effects of different thicknesses of TCLs on the morphology and photoelectrochemical performance of TNA films were investigated. The results indicated that TCLs with appropriate thickness could effectively improve the morphology and photoelectrochemical performance of TNA films. Compared with the TNA films based on TCL5, TCL10 and TCL30, the TNA film based on TCL20 exhibited more ideal and comprehensive photoelectrochemical performance. Moreover, dye-sensitized solar cells (DSSCs) based on this TNA film achieved the highest Jsc (10.2054 mA cm−2), Voc (0.5737 V), PCE (3.3%) and Pout (3.31 mW cm−2).
An anatase TiO 2 sol containing ultrafine TiO 2 crystallites (ca. 5 nm) was used to fabricate the dye-sensitized solar cells (DSSCs) with a compact layer, which was prepared by the peptization–hydrothermal method using the CF 3 COOH as peptizing agent. The dried sol was calcined at 300 °C for 1 h to eliminate the organics over the surface of TiO 2 and increase the crystallite size of the TiO 2 nanocrystals (the special surface area of the calcined TiO 2 decreased from 224.7 to 94.9 m 2 /g); and then it was used to prepare the paste for the porous layer of DSSCs. The compact layer was prepared by the diluted sol through the layer-by-layer (LBL) self assembly technique to control its thickness. The compact films derived from LBL self assembly method not only prevented the charge recombination at the conductor substrate/electrolyte interface but also improved the adhesion between the porous layer and the conductive layer on the substrate, which increased the number of the effective electron pathways with the short distance of the porous layer and consequently resulted in a better electrical contact. The photoelectron conversion efficiency of the DSSCs with the LBL films had increased apparently. In particular, a 12-layer TiO 2 /PSS LBL film of the DSSC led to a 24.5% increase in the photoelectron conversion efficiency from 5.93 to 7.38%.
A series of perovskite-based solar cells were fabricated wherein a compact layer (CL) of TiO 2 of varying thickness (0–390 nm) was introduced by spray pyrolysis deposition between fluorine-doped tin oxide (FTO) electrode and TiO 2 nanoparticle layer in perovskite-based solar cells. Investigations of the CL thickness-dependent current density–voltage ( J–V ) characteristics, dark current, and open circuit voltage ( V oc ) decays showed a similar trend for thickness dependence. A CL thickness of 90 nm afforded the perovskite-based solar cell with the maximum power conversion efficiency ( η , 3.17%). Furthermore, two additional devices, perovskite-based solar cell omitting hole transporting materials layer and cell without the TiO 2 nanoparticles, were designed and fabricated to study the influence of the CL thickness on different electron transport paths in perovskite-based solar cells. Solar cells devoid of TiO 2 nanoparticles, but with perovskite and organic hole-transport materials (HTMs), exhibited sustained improvement in photovoltaic performances with increase in the thickness of CL, which is in contrast to the behavior of classical perovskite-based solar cell and common solid state solar cell which showed optimal photovoltaic performances when the thickness of CL is 90 nm. These observations suggested that TiO 2 nanoparticles play a significant role in electron transport in perovskite-based solar cells.
Multifunctional and ultrathin tin oxide (SnO 2 ) compact layer is modified by europium ion doped ytterbium fluoride (YbF 3 :Eu 3+ ), which is first designed and fabricated by a facile spin-coating method for the dye-sensitized solar cell (DSSC). The device with SnO 2 /YbF 3 :Eu 3+ compact layer exhibits enhanced long-term stability and photoelectric conversion efficiency (PCE) compared to those of the device without compact layer. The enhanced long-term stability is due to the SnO 2 /YbF 3 :Eu 3+ compact layer can transform ultraviolet (UV) light into visible light to mitigate dye degradation . The enhanced PCE is associated with the reduced recombination rate of electrons, the enhanced short-wavelength light response, and the high transparency of the compact layer. Moreover, the novel strategy of preparation SnO 2 /YbF 3 :Eu 3+ compact layer is an universal method to adjust rare-earth species to achieve up- or down-conversion functions, and the multifunctional compact layer can be widely applied in the photovoltaic device .
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