Single-Crystalline Structure Assisted Revealing the Critical Factors for the Properties of All-Small-Molecule Organic Solar Cells

Abstract

All-small-molecule organic solar cells have attracted great interests due to their well-defined molecular structures and suitability for investigating the relationship between the structure and properties. Herein, two small-molecule donors (SMDs) based on DTBDT core with chlorine atoms and alkylsilyl side chains, namely, ZR-Si3 and ZR-Si4, are synthesized and their respective photovoltaic properties by blending them with IDIC-4Cl and Y6 are studied. The power conversion efficiency (PCE) based on IDIC-4Cl is higher than that of Y6 systems due to low driving force between the donors and Y6. Although the two IDIC-4Cl systems have similar morphology, the PCE of 10.10% is attained based on ZR-Si4, which is higher than that of ZR-Si3-based devices (8.12%). To obtain an in-depth insight into the structure and performance relationship, single crystals of two SMDs and acceptors are obtained successfully. The shortest π−π stacking distance of 3.43 Å and a transport channel between the layers are observed for ZR-Si4, which is beneficial for getting better performance.