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describing charge transport are the carrier mobility, charge generation/extraction, and carrier lifetime observed in fully assembled, operating solar cells. [5] There are several well-known experimental approaches toward estimation of these parameters including time-of-flight (TOF) photoconductivity, [6] space charge limited current (SCLC), [7] field-effect transistor (FET), [8] and charge extraction by linearly increasing voltage (CELIV). [9,10] However, each of them is hindered by an array of limitations. In principle, most commonly utilized TOF photoconductivity measurement is operated in direct current mode and requires application of very thick film in order to provide surface photogeneration for reliable observation of charge transport features, as well as the transit time. In addition, light bias is kept very low, ensuring charge carrier concentration to be much lower than the charge stored on the electrodes, resulting in constant electric field across the measured sample. These prerequisites are difficult to meet in the case of efficient thin film perovskite-based solar cells, especially when planar architecture is taken into consideration, as these devices are generally sub 500 nm thick. On the other hand, SCLC technique also comes with a set of drawbacks reflected through relationship between injected charge and distribution of occupancy within localized states, leading to oversimplification of results in respect to trapping states, sample homogeneity, temperature dependence, as well as quality of contact between electrodes and semiconductor. [11] In the case of charge mobility, poor injection of faster carriers in cells with unbalanced transport often leads to overestimation of retrieved values. Alternatively, dark injection SCLC can be utilized to study very thin films in a fashion highly similar to TOF, with exception of voltage step being used for generation of charge carriers instead of a laser pulse. The charge mobility obtained from FET measurement depends on the type of electrodes, semiconductor-dielectric interface, and the charge carrier concentration. Moreover, device geometry used for FET measurements differs considerably from diode configuration, thus charge transport properties obtained from FET architecture may not reliably reflect charge transport behavior of diode structures. CELIV has been widely used as a reliable tool in characterization of organic solar cells, [12,13] relying on triangle voltage Photoinduced charge selective carrier extraction by linearly increasing voltage technique allows straightforward assessment of charge transport properties within planar and mesostructured perovskite solar cells with respect to light intensity and signal delay time. Charge sensitive device architecture is realized through implementation of insulating layer between the anode or cathode to prevent extraction of unwanted type of carriers. Resulting behavior of comparatively efficient mesoporous and planar solar cells exhibits well balanced charge transport with slight dependence of charge mobili...

PbI-enriched mixed perovskite film [FAMAPb(IBr)] has been widely studied due to its great potential in perovskite solar cell (PSC) applications. Herein, a FAMAPb(IBr) film has been fabricated with the temperature-dependent optical absorption spectra utilized to determine its exciton binding energy. A ∼13 meV exciton binding energy is estimated, and a near-unity fraction of free carriers out of the total photoexcitons has been obtained in the solar cell operating regime at equilibrium state. PSCs are fabricated with this mixed perovskite film, but a significant electron transport barrier at the TiO-perovskite interface limited their performance. CsCO and CsI are then utilized as functional enhancers with which to substantially balance the electron and hole transport and increase the carriers (both electrons and holes) mobilities in PSCs, resulting in much-improved solar-cell performance. The modified PSCs exhibit reproducible power conversion efficiency (PCE) values with little hysteresis effect in the J-V curves, achieving PCEs up to 19.5% for the CsCO-modified PSC and 20.6% when subsequently further doped with CsI.

Operational stability and structural integrity of a poly(triarylamine) hole transporter and methylammonium lead halide absorber are investigated upon exposure to UV stress.

Titanium dioxide (TiO) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO nanoparticle (NP) suspension solution. The resulting TiO NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO layer for FAMAPb(IBr) based perovskite solar cells (PSCs). By varying the TiO NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO NHS distribution densities. The optimized PSC employing TiO NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a J of 23.8 mA cm, a V of 1.14 V and a FF of 0.71. Furthermore, the PSC possesses a reproducible PCE value with little hysteresis in its current density-voltage (J-V) curves. The small perturbation transient photovoltage (TPV) measurement reveals a longer free carrier lifetime within the TiO NHS based PSC than that in the TiO NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO NHSs a promising electron transport material for efficient photovoltaic devices.

An engineering approach is implemented for the performance and stability enhancement of perovskite solar cells, through the incorporation of bismuth telluride flakes in the electron transport layer (ETL) and as an interlayer on top of the ETL.

Gelatin-polyvinylpyrrolidone (PVP) and gelatin-poly(vinyl alcohol) (PVA) mucoadhesive buccal films loaded with propranolol hydrochloride (PRH) were prepared by semi-solid extrusion 3D printing. The aim of this study was to evaluate the effects of the synthetic polymers PVP and PVA on thermal and mechanical properties and drug release profiles of gelatin-based films. The Fourier-transform infrared spectroscopy showed that hydrogen bonding between gelatin and PVP formed during printing. In the other blend, neither the esterification of PVA nor gelatin occurred. Differential scanning calorimetry revealed the presence of partial helical structures. In line with these results, the mechanical properties and drug release profiles were different for each blend. Formulation with gelatin-PVP and PRH showed higher tensile strength, hardness, and adhesive strength but slower drug release than formulation with gelatin-PVA and PRH. The in silico population simulations indicated increased drug bioavailability and decreased inter-individual variations in the resulting pharmacokinetic profiles compared to immediate-release tablets. Moreover, the simulation results suggested that reduced PRH daily dosing can be achieved with prolonged-release buccal films, which improves patient compliance.

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