Pavel Hrzina

Photocurrent Spectroscopy of Perovskite Layers and Solar Cells: A Sensitive Probe of Material Degradation

Optical absorptance spectroscopy of polycrystalline CH3NH3PbI3 films usually indicates the presence of a PbI2 phase, either as a preparation residue or due to film degradation, but gives no insight on how this may affect electrical properties. Here, we apply photocurrent spectroscopy to both perovskite solar cells and coplanar-contacted layers at various stages of degradation. In both cases, we find that the presence of a PbI2 phase restricts charge-carrier transport, suggesting that PbI2 encapsulates CH3NH3PbI3 grains. We also find that PbI2 injects holes into the CH3NH3PbI3 grains, increasing the apparent photosensitivity of PbI2. This phenomenon, known as modulation doping, is absent in the photocurrent spectra of solar cells, where holes and electrons have to be collected in pairs. This interpretation provides insights into the photogeneration and carrier transport in dual-phase perovskites.

Using measurement of AC parameters for CIGS PV modules degradation studying

There are many diagnostic methods for PV modules parameters determination used. Most of them are based on measurement of static parameters, but therefore exist also measurement methods for AC parameters such a capacitance or impedance determination. In the paper is described Time Domain Reflectometry method which can be used for differentiation of PV modules with same static plate values. Different AC parameters can cause dissimilar behavior in alternating fields leading to premature degradation.

Parameters of the magnetic core and parasitic structure in RF SMPS circuit

This article describes the system for measurement of parasitic parameters of designed SMPS (switched mode power supply) structures operating at frequencies of hundreds of kHz. The method uses a comparison between simulation results and practical measurement. For simulation the most popular circuit simulators as PSPICE, PSIM, SIMULINK can be applied