The performance of perovskite solar cell (PSC) is highly sensitive to deposition conditions, the substrate, humidity, and the efficiency of solvent extraction. However, the physical mechanism involved in the observed changes of efficiency with different deposition conditions has not been elucidated yet. In this work, PSCs were fabricated by the antisolvent deposition (AD) and recently proposed air-extraction antisolvent (AAD) process. Impedance analysis and J-V curve fitting were used to analyze the photogeneration, charge transportation, recombination, and leakage properties of PSCs. It can be elucidated that the improvement in morphology of perovskite film promoted by AAD method leads to increase in light absorption, reduction in recombination sites, and interstitial defects, thus enhancing the short-circuit current density, open-circuit voltage, and fill factor. This study will open up doors for further improvement of device and help in understanding its physical mechanism and its relation to the deposition methods.

We for the first time report the incorporation of cobalt into a mesoporous TiO electrode for application in perovskite solar cells (PSCs). The Co-doped PSC exhibits excellent optoelectronic properties; we explain the improvements by passivation of electronic trap or sub-band-gap states arising due to the oxygen vacancies in pristine TiO, enabling faster electron transport and collection. A simple postannealing treatment is used to prepare the cobalt-doped mesoporous electrode; UV-visible spectroscopy, X-ray photoemission spectroscopy, space charge-limited current, photoluminescence, and electrochemical impedance measurements confirm the incorporation of cobalt, enhanced conductivity, and the passivation effect induced in the TiO. An optimized doping concentration of 0.3 mol % results in the maximum power conversion efficiency of 18.16%, 21.7% higher than that of a similar cell with an undoped TiO electrode. Also, the device shows negligible hysteresis and higher stability, retaining 80.54% of the initial efficiency after 200 h.

While 2D/3D layered perovskites have been the object of comprehensive researches principally focused on increasing the long-term stability observed in 3D perovskites, significant opportunities are still open concerning the application of different kinds of cations which are outside the sphere of primary amines, which are the cations most usually applied. Our results demonstrate that the materials and the solar cells prepared with dipropylammonium iodide (DipI), a bulky secondary ammonium cation of small size, lead to obtaining not only efficient and thermodynamically stable materials but also robust towards heat stress. Time-resolved studies point out longer carrier´s lifetime for 2D/3D layered perovskites fabricated with this bulky cation than systems based on bulky primary ammonium cations, which allowed us to obtain PCE=12.51% (n=10), 15.78% (n=50) and 17.90% (n=90). We determine that the concentration of perovskite material after 240 min at 100° C is until 575% greater in the 2D/3D perovskite (n=10) than the observed in 3D perovskite films. The material stability also improves the thermal stability of the photovoltaic devices presenting an efficiency drop of just 4% for n=50 and n=10 after thermal annealing while the performance drop for reference 3D samples in the same conditions was of higher than 80%.

The procedure employed for the sensitization of mesoporous photoanodes affects strongly the final performance of sensitized devices, especially when semiconductor quantum dots and quantum rods are used as sensitizers. In this work the effect of three different sensitizing methods in the final cell performance was analyzed. The TiO 2 films were sensitized with CdS QDs grown by successive ionic layer adsorption and reaction, SILAR, and with CdSe quantum rods deposited by electrophoretic and pipetting methods. Several configurations of the sensitizers and combinations of sensitization methods were tested. 4% photoconversion efficiencies were obtained for TiO 2 electrodes sensitized with CdS and CdSe by electrophoretic and pipetting respectively, while for the sensitizer with both techniques the efficiency was 4.7%. This high efficiency is mainly due to the high fill factor (60%) and the photocurrents (13.1 mA/cm 2 ) obtained by the correct combination of near-infrared and visible light photoabsorption, the better CdSe QRs distribution in the TiO 2 film and a passivation of the TiO 2 nanocrystals. Electrochemical impedance measurements has been analyzed and discussed in detail providing a detailed analysis of recombination resistance and charge transport processes. These parameters have been correlated with the cell performance.

A multilayered semiconductor sensitizer structure composed of three differently sized CdSe quantum rods (QRs), labeled as Q530, Q575, Q590, were prepared and deposited on the surface of mesoporous TiO2 nanoparticles by electrophoretic deposition (EPD) for photovoltaic applications. By varying the arrangement of layers as well as the time of EPD, the photoconversion efficiency was improved from 2.0% with the single layer of CdSe QRs (TiO2/Q590/ZnS) to 2.9% for multilayers (TiO2/Q590Q575/ZnS). The optimal EPD time was shorter for the multilayered structures. The effect of CdS quantum dots (QDs) deposited by successive ionic layer adsorption and reaction (SILAR) was also investigated. The addition of CdS QDs resulted in the enhancement of efficiency to 4.1% for the configuration (TiO2/CdS/Q590Q575/ZnS), due to increased photocurrent and photovoltage. Based on detailed structural, optical, and photoelectrical studies, the increased photocurrent is attributed to broadened light absorption while the increased voltage is due to a shift in the relevant energy levels.

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