The aim of this work is to investigate the degradation of perovskite solar cells (PSCs) by means of impedance spectroscopy, a highly sensitive characterization technique used to establish the electrical response of a device in a nondestructive manner. In this paper, PSCs with two different electron transport layers (ETLs) are studied: PSCs with undoped SnO₂ as an ETL are compared to PSCs with an ETL composed of graphene-doped SnO₂ (G-SnO₂). Experimental data were collected immediately after fabrication and after one week, monitoring both impedance spectroscopy and dark current-voltage (I-V) curves. It was observed that, in the case of the undoped PSCs, the degradation of the solar cells affected both the AC behavior of the devices, modifying the associated Nyquist plots, and the DC behavior, observable from the dark I-V measurements. Conversely, the solar cells with G-SnO₂ showed no variation. Considering the Nyquist plots, a quantitative analysis was performed by comparing the parameters of a proper equivalent circuit model. The results were coherent with those achieved in the DC analysis, thus proving that the analysis of impedance spectra, supported with dark I-V curves, allows one to gain a deeper knowledge of the degradation phenomena of perovskite solar cells. This study opens the door for further improvement of these devices through a better understanding of their electrical behavior.

In this work, front contacts for graphene-based solar cells are made by means of colloidal graphite instead of gold. The performance is characterized by exploiting impedance spectroscopy and is compared to the standard gold contact technology. Impedance data are analysed through equivalent circuit representation in terms of lumped parameters, suitable to describe the complex impedance in the frequency range considered in the experiments. Using this approach, capacitance–voltage of the considered graphene–silicon solar cell is found and the barrier height forming at the graphene–silicon interface is extracted.

In this article, the effect of graphene/silicon Schottky junction solar cells (G/Si SJSCs) encapsulation is investigated in terms of capacitance–voltage ( C – V ) curves in the forward bias region. Capacitance behavior can give accurate information on interface properties, especially when it is considered at positive voltage. The detection of a double peak on such curve is related to nonuniform interface properties at the graphene/silicon interface. To passivate the interface, G/Si SJSCs have been exposed to HNO $_{\text{3}}$ vapors and the effectiveness of HNO $_{\text{3}}$ doping has been exploited as well as its volatility, assessing the need for encapsulation. C – V curves collected over time from doped unencapsulated G/Si SJSCs clearly exhibited a modification of capacitance behavior, revealing a fading of doping beneficial effects over a week. On the contrary, C – V curves acquired from encapsulated samples evidence that capacitance behavior did not modify over time.