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

Abstract

AbstractEmploying a large dipole interlayer has recently been one of the most captivating interfacial engineering approaches in organic solar cells (OSCs). In this work, the effect of using green‐solvent processable molecules with large dipole moments as electron extraction layers (DM‐EELs) on OSCs’ stability is investigated. The inverted OSCs are based on two donor–acceptor systems, with histidine and sarcosine as representative DM‐EELs and with ZnO as a control EEL. Stability results illustrate that while the dominant degradation mechanism depends on the donor–acceptor system (photoinduced degradation vs temporal degradation), using DM‐EELs substantially suppresses degradation and enhances stability in both cases. The voltage‐dependent ideality factor characteristics show that the DM‐EEL OSCs exhibit minimal recombination mechanism changes even after UV exposure. By contrast, ZnO cells are limited by significant shunt formation and UV‐induced surface recombination. Low‐temperature measurements verify that unlike the indium tin oxide (ITO)/ZnO contact, the ITO/DM‐EEL contact is not affected by trap states or work function variations. As a result, the ITO/DM‐EEL contact maintains its electron‐selectivity and resists UV‐induced surface recombination observed in the ZnO cells. The results show that using green‐solvent processable materials with large dipole moments as EELs can provide a universal route for enhancing the stability of inverted OSCs.