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We present a comprehensive approach to the characterization and modeling of photovoltaic metal-halide perovskite single junction devices and perovskite-silicon tandem solar cells. The framework is based on 1D opto-electronic device simulation in steady-state and transient modes as well as frequency domain including specific features of the perovskite materials such as mobile ions, combined with a broad variety of device characterization experiments. As a salient feature, advanced optimization algorithms are used for reliable parameter extraction and opto-electronic device optimization purposes in both single junction and tandem solar cell architectures.

We discuss the numerical optimization of organic and hybrid multijunction solar cell devices, using an integrated optoelectronic device simulation approach that captures the essential properties of the complex multilayer structures, such as, light scattering at both macroscopic and rough thin film textures, resonator effects in coherent stacks, and the impact of organic interface properties for the design of efficient recombination layers. The optimization capabilities of the numerical device simulation framework are illustrated on the examples of textured perovskite-silicon and all-organic tandem solar cells.

We present an optical model implemented in the commercial software SETFOS 4.6 for simulating perovskite/silicon monolithic tandem solar cells that exploit light scattering structures. In a first step we validate the model with experimental data of tandem solar cells that either use front- or rear-side textures and extract the internal quantum efficiency of the methyl-ammonium lead iodide (MALI) perovskite sub-cell. In a next step, the software is used to investigate the potential of different device architectures featuring a monolithic integration between the perovskite and silicon sub-cells and exploiting rear- as well as front-side textures for improved light harvesting. We find that, considering the available contact materials, the p-i-n solar cell architecture is the most promising with respect to achievable photocurrent for both flat and textured wafers. Finally, cesium-formamidinium-based perovskite materials with several bandgaps were synthetized, optically characterized and their potential in a tandem device was quantified by simulations. For the simulated layer stack and among the tested materials with bandgaps of 1.7 and 1.6 eV, the one with 1.6 eV bandgap was found to be the most promising, with a potential of reaching a power conversion efficiency of 31%. In order to achieve higher efficiencies using higher band-gap materials, parasitic absorptance in the blue spectral range should be further reduced.

This paper pertains to the analysis of natural balancing properties of an N-cell modular multilevel converter under phase-shifted pulse width modulation control schemes. The key enabling feature for the natural balancing analysis is a set of linear transformations of the input space and state space of the overall system. In the transformed space, we use frequency domain methods to describe the self-balancing properties of the converter. The crux of our proposal is showing that all the cell capacitor voltages converge exponentially fast to a common level; hence achieving natural balancing. The accuracy of the transformed model is verified through comparison with a detailed time-domain simulation of the original system.

Natural balancing of the flying capacitor converter is activated when the converter is operating with phase shifted carrier PWM and the carriers are exactly interleaved. The mechanism is stable and has many benefits but the dynamic response can be slow. In this paper a novel active balancing approach, based on the application of an off-line optimized phase shift of the individual carriers during the re-balancing regime, will be introduced and discussed.