Capacitance spectroscopy of thin film formamidinium lead iodide based perovskite solar cells

This work concerns the interpretation of capacitance spectroscopy results in perovskite based solar cells. Based on the deep level transient spectroscopy and admittance spectroscopy results, we present arguments that the observable signals in perovskite based solar cells come from anion migration rather than being a response from deep trap energy levels. The ion migration parameters, such as activation energy and ion concentration, are calculated and compared to theoretical values for different migration paths of ions in perovskites. Those parameters evolve with time, reflecting in the degradation of the cells, which we propose to link with a change in the anion migration path in perovskit

Bilayer Hybrid Solar Cells Based on Triphenylamine−Thienylenevinylene Dye and TiO2

Photoinduced energy conversion from multilayers of organic dye on dense TiO2 films was investigated in bilayer hybrid solar cells. Dye layers of varying thicknesses were prepared by spin-casting the star-shaped dye [tris(dicyano-vinyl-2-thienyl)phenyl]amine (1) from solutions onto dense TiO2 on conducting glass substrates. A spin-cast layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and graphite powder was used for contacting the devices. Excitons generated in the dye multilayer contribute to the power conversion efficiency, reaching a maximum of ca. 0.3% at a dye layer thickness of ca. 8 nm for the devices described herein. For dye layers exceeding 5 nm, the cell performance becomes limited by the exciton diffusion length LED and the hole mobility in the organic layer. Using dye multilayers is a viable way to increase light harvesting in solid-state dye-sensitized solar cells

Exciton enhanced dye sensitized solar cells

Date du colloque&nbsp;: 05/2009</p

Temperature Dependent Crystallization Mechanisms of Methylammonium Lead Iodide Perovskite From Different Solvents

Hybrid perovskites are a novel type of semiconductors that show great potential for solution processed optoelectronic devices. For all applications, the device performance is determined by the quality of the solution processed perovskite thin films. During solution processing, the interaction of solvent with precursor molecules often leads to the formation of solvate intermediate phases that may diverge the crystallization pathway from simple solvent evaporation to a multi step formation process. We here investigate the crystallization of methylammonium lead iodide MAPbI 3 from a range of commonly utilized solvents, namely dimethyl sulfoxide DMSO , N,N dimethylformamide DMF , N methylpyrrolidone NMP , and gamma butyrolactone GBL at different temperatures ranging from 40 C to gt;100 C by in situ grazing incidence wide angle X ray scattering GIWAXS measurements. For all solvents but GBL, we clearly observe the formation of solvate intermediate phases at moderate processing temperatures. With increasing temperatures, an increasing fraction of the MAPbI 3 perovskite phase is observed to form directly. From the temperature dependence of the phase formation and phase decomposition rates, the activation energy to form the MAPbI 3 perovskite phase from the solvate phases are determined as a quantitative metric for the binding strength of the solvent within the solvate intermediate phases and we observe a trend of DMSO gt; DMF gt; NMP gt; GBL. These results enable prediction of processing temperatures at which solvent molecules can be effectively remove

One pot synthesis of a stable and cost effective silver particle free ink for inkjet printed flexible electronics

Silver particle free inks display immense superiority and potential over silver nanoparticle based inks in the aspect of synthesis, flexibility and low temperature processing, which has attracted considerable research interest as an alternative for fabricating conductive structures in recent years. Although recent research on silver particle free inks has led to beneficial results, there are still some drawbacks some of the inks are chemically unstable and hence are not suitable for industrial inkjet printing process, although they have good conductivity; while others are cheap in terms of raw material costs but are complicated to make due to the complex synthetic route or using hazardous procedures, or are not compatible with inkjet printing. Therefore, it will be advantageous to develop a stable, cheap and inkjet printable silver particle free ink using a simple synthetic procedure. Alcohols are favorable solvents for silver particle free inks that can provide the ink with essential fluid properties for inkjet printing. However, they have some negative effects on the ink performance due to their physicochemical properties, which should be avoided. In this work, a simple do it yourself silver particle free ink is presented, which shows high chemical stability, low cost and good printability. The ink is formulated via a simple silver oxalate precursor route in alcohols. The fluid property, thermal property, stability and electrical performance of the inks based on different alcohols were investigated and optimized to obtain the final ink for printing on glass and flexible polyimide substrates. The printed Ag features yielded a resistivity of 15.46 amp; 956; amp; 937; cm at a sintering temperature of 180 C, which is equivalent to 10 times bulk silver. Based on a comprehensive assessment, we can offer a low cost, easy to make, reliable and highly competitive ink for flexible printed electronic

Large area inkjet printed metal halide perovskite LEDs enabled by gas flow assisted drying and crystallization

We demonstrate the upscaling of inkjet printed metal halide perovskite light emitting diodes. To achieve this, the drying process, critical for controlling the crystallization of the perovskite layer, was optimized with an airblade like slit nozzle in a gas flow assisted vacuum drying step. This yields large, continuous perovskite layers in light emitting diodes with an active area up to 1600 mm

Finally, inkjet printed metal halide perovskite LEDs utilizing seed crystal templating of salty PEDOT PSS

Solution processable metal halide perovskites are increasingly implemented in perovskite based light emitting diodes PeLEDs . Especially green PeLEDs based on methylammonium lead bromide MAPbBr3 composites exhibit impressive optoelectronic properties, while allowing processing by low cost and upscalable printing methods. In this study, we have investigated the influence of potassium chloride KCl blended into the common hole injection material poly 3,4 ethylenedioxythiophene polystyrene sulfonate PEDOT PSS to boost PeLED device performance. The inclusion of KCl firstly results in a change in morphology of the PEDOT PSS layer, which then acts as a template during deposition of the perovskite layer. A MAPbBr3 polyethylene glycol PEG composite was used, which does not require the deposition of an anti solvent droplet to induce preferential perovskite crystallization and is therefore suitable for spin coating and scalable inkjet printing processes. PeLEDs utilizing the KCl induced templating effect on a planar PEDOT PSS MAPbBr3 PEG architecture show improved performance, predominantly due to improved crystallization. PeLEDs incorporating spin coated perovskite layers yield a 40 fold increase in luminance 8000 cd m 2 while the turn on voltage decreases to 2.5 V. KCl modified PEDOT PSS contact layers enabled the realization of inkjet printed PeLEDs with luminance increased by a factor of 20 at a maximum of 4000 cd m 2 and a turn on voltage of 2.5 V. This work paves the way for inkjet printed perovskite light emitting devices for a wide variety of low cost and customizable application

Gas flow assisted vacuum drying Identification of a novel process for attaining high quality perovskite films

Controlling the nucleation and crystal growth in solution processed metal halide perovskite MHP thin films is the pivotal point in fabricating homogenous and pinhole free films. Using scalable coating and printing techniques, vacuum and gas flow assisted drying processes turn out to be the most promising methods to induce nucleation and crystallization. Yet, the exact interplay and nature of these processes are unclear. In our work, we optically monitor these processes in situ. For the first time, we can show that a controlled venting of the vacuum chamber and the use of a subsequent gas flow are key to achieve homogenous nucleation. Utilizing this gas flow assisted vacuum drying process, we find that regular, optically dense and pinhole free MHP layers can be fabricated via inkjet printing, which yield solar cells with a power conversion efficiency of 16 , as compared to 4.5 for vacuum dryin

Contribution from a hole-conducting dye to the photocurrent in solid-state dye-sensitized solar cells

The hole transporting medium in solid-state dye-sensitized solar cells can be utilized to harvest sunlight. Herein we demonstrate that a triphenylamine-based dye, used as hole-transporting medium, contributes to the photocurrent in a squaraine-sensitized solid-state dye-sensitized solar cell. Steady-state photoluminescence measurements have been used to distinguish between electron transfer and energy transfer processes leading to energy conversion upon light absorption in the hole-transporting dye

Perfluorinated Self Assembled Monolayers Enhance the Stability and Efficiency of Inverted Perovskite Solar Cells

Perovskite solar cells are among the most exciting photovoltaic systems as they combine low recombination losses, ease of fabrication, and high spectral tunability. The Achilles heel of this technology is the device stability due to the ionic nature of the perovskite crystal, rendering it highly hygroscopic, and the extensive diffusion of ions especially at increased temperatures. Herein, we demonstrate the application of a simple solution-processed perfluorinated self-assembled monolayer (p-SAM) that not only enhances the solar cell efficiency, but also improves the stability of the perovskite absorber and, in turn, the solar cell under increased temperature or humid conditions. The p-i-n-type perovskite devices employing these SAMs exhibited power conversion efficiencies surpassing 21%. Notably, the best performing devices are stable under standardized maximum power point operation at 85 °C in inert atmosphere (ISOS-L-2) for more than 250 h and exhibit superior humidity resilience, maintaining ∼95% device performance even if stored in humid air in ambient conditions over months (∼3000 h, ISOS-D-1). Our work, therefore, demonstrates a strategy towards efficient and stable perovskite solar cells with easily deposited functional interlayers