Achieving 10.5% efficiency for inverted polymer solar cells by modifying the ZnO cathode interlayer with phenols

Abstract

Interfacial engineering is crucial to improve photovoltaic performance. In this work, a single-junction inverted polymer solar cell (IPSC) is fabricated where the ZnO cathode interlayer (CIL) is modified with phenols (both on the ZnO surface and in blend). By using this strategy, power conversion efficiency (PCE) can be remarkably enhanced to 10.5% with PTB7-Th:PC₇₁BM as the active layer, which is an ∼22% increase compared to that of a control device (8.59%) without modification. Meanwhile, the long-term stability of the modified device is also improved relevant to the control one. The improvement of device performance and stability was attributed to the better contact with the active layer, decreased work function, increased electron transport and reduced series resistance, induced by the dehydration between phenols and hydroxyl groups on the ZnO surface certified by in situ Fourier transform infrared spectroscopy.