Researchers developed a perovskite solar cell with high power-conversion efficiency (>20%) and intense electroluminescence yield (0.5%).

TiO 2 /FTO, the cross sectional scanning electron microscopy (SEM) image of which is shown in Fig. 1a. Employing this solar cell configuration, we achieve the best PCE of 21.6% with a PMMA concentration C PMMA =0.6mg/ml. The photovoltaic metrics of the device are as follows: short-circuit current density (J SC ) = 23.7 mA cm -2 , open circuit voltage (V OC ) = 1.14 V, and a fill factor (FF) = 0.78 (Fig. 1b). One of the devices was sent for certification to Newport Corporation PV Lab, an accredited PV testing laboratory, confirming a PCE of 21.02% (supplementary Fig.1 Fig. 3, Tab. 2a and 2b). The photovoltaic metrics of the PSCs fabricated from PTNG method varying C PMMA are summarized in Fig. 1c.Upon increasing the PMMA concentrations (C PMMA , mg/ml) in mixed chlorobenzene and toluene (volume ratio of cholorobenzene and toluene is 9:1) solution, the PCE first augments and subsequently decreases with a peak at C PMMA = 0.6. Upon increasing the C PMMA from 0 to 0.6 mg/ml, the V oc rises from 1.10V to 1.14 V, and the FF from 0.74 to 0.78. To further examine the crystal structure, we conducted thin layer X-ray diffraction (XRD) measurements for perovskite films deposited on m-TiO 2 /blTiO 2 /FTO substrates (Fig.3a). The peak at 12.5 o arises from the (001) lattice planes of hexagonal (2H polytype) PbI 2. The excess PbI 2 is believed to passivate surface defects, increasing the solar cell performance 13 . All the samples show the same trigonal perovskite phase with the dominant (111) lattice reflection. We speculate the (111) plane to exhibit the smallest surface energy because the majority of grains exhibit this orientation to minimize the total Gibbs free energy of the system. With increasing C PMMA , the (111) oriented grains grew faster by consuming neighboring non-oriented crystals, either by regular grain growth or grain attachment, as evidenced by the increased ratio between the (111) and (123) peak at 13.9 ° and 31.5° in the presence of PMMA. By taking the full width at half maximum (FWHM) of the (111) reflection, we calculate the crystallite size using Scherrer's equation. Their dimension increases from 41 to 55, 70, 94, and 112 nm by increasing C PMMA from 0 to 4mg/ml.We attribute the larger crystal sizes to the templating effect of PMMA on the crystal The X-ray photoelectron spectroscopy (XPS) in Fig. 3d shows Pb 4f spectra.There are two main peaks Pb 4f7/2 and Pb 4f5/2 at 138 and 142.8 eV, respectively.We attribute the two small peaks located at 136.4 and 141.3 eV to the presence of In conclusion, we introduce a new method for preparing high-electronic quality perovskite films and implement it for the fabrication of PSC with excellent performance their certified PCE attaining 21 %. Further development of the method will enable further performance gains. Acknowledgement:

Metal halide perovskite solar cells (PSCs) currently attract enormous research interest because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication costs, but their practical development is hampered by difficulties in achieving high performance with large-size devices. We devised a simple vacuum flash-assisted solution processing method to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas. This enabled us to fabricate solar cells with an aperture area exceeding 1 square centimeter, a maximum efficiency of 20.5%, and a certified PCE of 19.6%. By contrast, the best certified PCE to date is 15.6% for PSCs of similar size. We demonstrate that the reproducibility of the method is excellent and that the cells show virtually no hysteresis. Our approach enables the realization of highly efficient large-area PSCs for practical deployment.

We report a pump−probe spectroscopy study of electron injection rates in dye-sensitized solar cell (DSSC) devices. We examine the case of working devices employing an N719 ruthenium sensitizer and an iodide electrolyte. Electron injection is found to occur mainly on a sub-100 fs time scale, followed by a slower component with a lifetime of 26.9 ps, in accordance with previous reports on model samples. The amplitude of this latter component varies with electrolyte composition from 25 to 9%. The appearance of slower components in the electron injection dynamics may be attributed to an aggregated or weakly bound state of the surface-adsorbed N719 sensitizer. Further measurements are reported varying the cell light bias and load conditions, revealing no influence on electron injection dynamics. No other electron injection event is found to occur up to 1 ns. These results show no evidence for a slowdown of electron injection under working conditions compared to model systems for the electrolytes examined in this study. SECTION: Kinetics and Dynamics D ye-sensitized solar cells (DSSCs) can efficiently convert solar radiation into electricity by means of a molecular or quantum dot light harvester anchored on a wide-band-gap mesoporous semiconductor film. Electron injection from the photoexcited light harvester into the conduction band of the semiconductor, typically TiO 2 , is the first reaction in the photoconversion process.

Employing a mesoscopic titania photoanode whose bilayer structure was judiciously selected to fit the optoelectronic characteristics of the Ru-based heteroleptic complex Na-cis-Ru(4,4'-(5-hexyltiophen-2-yl)-2,2'-bipyridine)(4-carboxylic-acid-4'-carboxylate-2,2'-bipyridine)(thiocyanate)(2), coded as C101, we investigated the effect of temperature for dye adsorption on the photovoltaic performance of dye-sensitized solar cells (DSCs). We found a significant efficiency enhancement upon lowering the temperature applied during the sensitizer uptake from solution. When the dye adsorption was performed at 4 °C, the photovoltaic performance parameters measured under standard reporting conditions (AM1.5 G sunlight at 1000 W/m(2) intensity and 25 °C), i.e., the open circuit voltage (V(oc)), the short circuit photocurrent density (J(sc)), the fill factor (FF), and consequently the power conversion efficiency (PCE), improved in comparison to cells stained at 20 and 60 °C. Results from electrochemical impedance spectroscopy (EIS) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) show that the self-assembled layer of C101 formed at lower temperature impairs the back-electron transfer from the TiO(2) conduction band to the triiodide ions in the electrolyte more strongly than the film produced at 60 °C. Profiting from the favorable influence that the low-temperature dye uptake exerts on photovoltaic performance, we have realized DSCs showing a power conversion efficiency of 11.5%.