Reducing ultraviolet-induced open-circuit voltage loss in inverted organic solar cells by maintaining charge selectivity of the electron collection contact using polyethylenimine

Significant Photostability Enhancement of Inverted Organic Solar Cells by Inserting an N-Annulated Perylene Diimide (PDIN-H) between the ZnO Electron Extraction Layer and the Organic Active Layer

“…In the cells with ZnO, this qualitative match along with the increase in dark reverse current suggests that a combination of two interrelated phenomena, the reduction in the contact selectivity through shunting and changes in recombination mechanisms/rates, accounts for a significant part of photodegradation in these cells, consistent with previous reports. 31,41 In contrast, the stable trend of the ideality factor along with the low reverse current of the OSCs with ZnO/PDIN-H demonstrates that these cells maintain their rectifying behavior and recombination mechanism/rate upon prolonged irradiation.…”

“…Unlike in the cells with ZnO, the reverse current does not increase in the cells with ZnO/PDIN-H during the whole UV exposure. It has been demonstrated that an increase in the dark reverse current upon UV exposure occurs primarily from the loss of the charge selectivity of the contacts. , Because under reverse voltage, the ITO is held at a more positive potential relative to the Al electrode, an increase in the current reflects an increase in either hole injection through the ITO/EEL contact or electron injection through the MoO 3 /Al contact. Since apart from the EELs, the OSCs are structurally identical, the difference in reverse current must be associated with the EELs and arises from increased hole injection over time in the ZnO EEL case, pointing to a deterioration in the hole-blocking nature of the ITO/EEL contact.…”

The Use of Green‐Solvent Processable Molecules with Large Dipole Moments in the Electron Extraction Layer of Inverted Organic Solar Cells as a Universal Route for Enhancing Stability

“…ZnO sol-gel was prepared in the same way reported previously, resulting in a 30 nm thick film. [24,25] For DM-EELs preparation, 10 mg of Histidine (Millipore-Sigma) was dissolved in 10 mL of ethanol:DI-water (1:1) mixture and was stirred at 400 rpm for 1 h. For coating, the solution was filtered through a 0.22 µm polypropylene before spin coating at 5000 rpm for 60 s and annealing at 110 °C for 10 min. Sarcosine processing was similar to Histidine, apart from being dissolved in a 1-Propanol:DIwater (1:1) mixture.…”

“…[21][22][23] Recently, we and others have found that exposure of ZnO EELs to UV irradiation (in the solar spectrum) leads to a loss in their electron-selectivity and that the phenomenon plays a major role in the low photostability of OSCs. [21][22][23][24][25] Some approaches have been proposed to overcome this UV-induced degradation, such as applying UV treatments to the ZnO layer before active layer deposition, [26] adding a bilayer EEL, [25] or doping the ZnO layer. [20,27] These methods, however, increase the manufacturing complexity and cost.…”

“…We recently found that using polyethyleneimine as a large dipole moment electron extraction layer (DM-EEL) can lead to photostability enhancement in OSCs. [24] Therefore, in this work, we systematically study the stability behavior of OSCs with other green-solvent processable DM-EELs and investigate their influence on UV-induced electron-selectivity reduction. The latter being a primary failure mechanism in the case of OSCs with a ZnO EEL.…”