Degradation Analysis of Encapsulated and Nonencapsulated TiO2/PTB7:PC70BM/V2O5 Solar Cells under Ambient Conditions via Impedance Spectroscopy

Inverted organic cells are promising devices for sustainable and low-cost future electric generation. In this work, we present the degradation mechanisms studied in ITO/TiO2/PTB7:PC70BM/V2O5/Ag inverted organic solar cells (iOSCs) by impedance spectroscopy (IS). Measurements were performed on encapsulated (controlled environment) and nonencapsulated (ambient condition) cells following their temporal evolution under AM1.5 illumination for several voltage biases. From the impedance spectra, analyzed in terms of resistive/capacitive equivalent circuits, we were able to identify that the most sensitive layers inside of the device are contact layers. According with presented, IS technique is useful for determining the materials that have more influence on the degradation of organic solar cells. We demonstrate that IS is a powerful technique to identify the limiting mechanisms and to establish the limiting materials inside of the iOSCs.