Cathode Interlayer Engineering for Efficient Organic Solar Cells under Solar Illumination and Light-Emitting Diode Lamp

Abstract

Organic solar cells (OSCs) have become a potential energy source for indoor light harvesting in recent years as they have witnessed a record power conversion efficiency (PCE) of over 30% under indoor lights. Among various strategies, interlayer engineering is one of the important factors in improving the performance of OSCs. Here, we reported an efficient OSC based on PM6:Y6 photoactive layer showing an excellent PCE of ~22% and ~14% under light-emitting diode (LED, 1000-lx) and 1-sun (AM1.5 G) conditions, respectively. The performance of OSCs was optimized by systematically investigating the optical, electrochemical, and morphological characteristics of three different cathode interlayers (CILs) named as: PEIE, ZnO, and ZnO/PEIE (bilayer). The high transmittance (~90%), suitable work function (~4.1 eV), and improved surface morphology (RMS: 2.61 nm) of the bilayer CIL contributes in improving the performance of OSCs. In addition, the suppressed charge recombination and improved charge carrier transport are attributed to high shunt resistance and appropriate energy levels alignment between photoactive layer and bilayer CIL. The findings in the study might provide guidelines for designing novel interlayers in the development of efficient OSCs for different illumination conditions.