Tamara Merckx

Interconnection Optimization for Highly Efficient Perovskite Modules

This paper reports on the analysis and comparison of mechanical and laser patterning in the fabrication of perovskite thin-film photovoltaic modules. Besides stability, device upscaling and module fabrication is akey challenge for the commercialization of perovskite photovoltaics. Here, the focus is on the optimization of the P2 interconnection that represents the electrical connection between serially connected cells in a module. The specific contact resistivity for P2 interconnection is determined by using an enhanced transmission line method. Mechanical or laser patterning are used to fabricate 4 cm2 modules with aperture area efficiencies of up to 15.3% and geometrical fill factors as high as 94%. With the application of a simulation program with an integrated circuit emphasis-based electrical device model, the interconnection losses are quantified, and optimal designs for perovskite modules are presented.

Reconsidering figures of merit for performance and stability of perovskite photovoltaics

The development of hybrid organic-inorganic halide perovskite solar cells (PSCs) that combine high performance and operational stability is vital for implementing this technology. Recently, reversible improvement and degradation of PSC efficiency have been reported under illumination-darkness cycling. Quantifying the performance and stability of cells exhibiting significant diurnal performance variations is challenging. We report the outdoor stability measurements of two types of devices showing either reversible photo-degradation or reversible efficiency improvement under sunlight. Instead of the initial (or stabilized) efficiency and T80 as the figures of merit for the performance and stability of such devices, we propose using the value of the energy output generated during the first day of exposure and the time needed to reach its 20% drop, respectively. The latter accounts for both the long-term irreversible degradation and the reversible diurnal efficiency variation and does not depend on the type of process prevailing in a given perovskite cell.

Outdoor Measurement and Modeling of Perovskite Module Temperatures

Abstract Photovoltaic cells and modules are exposed to partially rapid changing environmental parameters that influence the device temperature. The evolution of the device temperature of a perovskite module of 225 cm2 area is presented during a period of 25 days under central European conditions. The temperature of the glass–glass packaged perovskite solar module is directly measured at the back contact by a thermocouple. The device is exposed to ambient temperatures from 3 to 34 °C up to solar irradiation levels exceeding 1300 W m−2. The highest recorded module temperature is 61 °C under constant high irradiation levels. Under strong fluctuations of the global solar irradiance, temperature gradients of more than 3 K min−1 with total changes of more than 20 K are measured. Based on the experimental data, a dynamic iterative model is developed for the module temperature evolution in dependence on ambient temperature and solar irradiation. Furthermore, specific thermal device properties that enable an extrapolation of the module response beyond the measured parameter space can be determined. With this set of parameters, it can be predicted that the temperature of the perovskite layer in thin‐film photovoltaic devices is exceeding 70 °C under realistic outdoor conditions. Additionally, perovskite module temperatures can be calculated in final applications.

Blade coating of diketopyrrolopyrrole based organic photovoltaics from non-halogenated solvent systems

The need for scalable and environmentally friendly deposition of organic semiconductors is mounting, as lab-scale solution processed organic photovoltaic (OPV) devices have been certified with 10.8% efficiency. The replacement of toxic halogenated solvents is a priority in the commercialization of solution processed OPV. Here we introduce several solvent systems based on thiophene, tetraline, 1,2,4-trimethylbenzene, xylene, and anisole for the blade coating of diketopyrrolopyrrole-based polymer: fullerene OPV devices. These devices attain 6.1% efficiency, greater than the commonly used chloroform:ortho-dichlorobenzene solvent systems for the same polymers, and without involving the post-deposition annealing treatments nor additives typically implemented for non-halogenated inks. Furthermore, the solubility of the material was investigated with Hansen Solubility Parameters, and coatability on a variety of substrates was probed via contact angle measurements. This work enables a new non-halogenated solvent route for the scalable fabrication of organic electronics.