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

Abstract

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/TiO 2 /PTB7:PC 70 BM/V 2 O 5 /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.

Three Destinies of Solution-Processable Polymer Light-Emitting Diodes under Long-Time Operation

“…Impedance spectroscopy allows to obtain information about the changes in the interfaces caused by the degradation of the device during electrical operation [20]. IS allows to effectively monitor the changes in the electrical parameters of organic devices over time, caused by the action of water or oxygen molecules [21]. The increase in impedance is so great that the data cannot be plotted on one graph (Figure 6a-c, mind the scale).…”

Photostability Study of Inverted Polymer Solar Cells Under AM 1.5G and LED Illumination via Impedance Spectroscopy

“…It can be seen that all plots over the degradation time show typical arc behavior, indicates that the equivalent 3RC circuit model is suitable for these spectra. Moreover, the diameter of arc increases as the aging time increases, suggesting an increased bulk resistance of PTB7-Th:PC 70 BM devices [29]. It is worth noting that the diameter of the arc is directly related to the value of the resistance.…”

“…Different optoelectronic techniques are used to monitor degradation and gain insights into degradation mechanisms within the device [27], [28]. Impedance spectroscopy (IS) in particular can measure the complex dielectric properties of the material by perturbing a small frequency-modulated (AC) signal on the direct current (DC) bias voltage in terms of frequency spectrum [29]. The extracted frequency-dependent impedance can be interpreted in terms of the equivalent circuits model with resistive/capacitive (RC) elements to describe the internal process of PSCs occurring at different time scales during the degradation [30].…”

Effects of Annealing Temperature on the Performance of Organic Solar Cells Based on Polymer: Non-Fullerene Using V2O5 as HTL

“…6a. The RC elements (R i C i ; i = 1, 2 and 3) can be correlated to the different layers involved in the charge-transferring process (TiO x , bulk, and V 2 O 5 ), by calculating their theoretical capacitance as we report elsewhere [49]. Table 2 summarizes the values of RC elements for TiO x , bulk, and V 2 O 5 layer used to fitting the IS spectra of Type A4 and Type B4 devices at 3 different bias voltages.…”