Presentation Information
[8a-S202-2]Structural Analysis of bulk heterojunction of non-fullerene solar cells
〇Shin Inamoto1, Chizuru Asahara1, Daichi Shirakura1, Masahiro Kunisu1, Wakako Hara1 (1.Toray Research Center)
Keywords:
solar cell,organic photovoltaics,electron microscope
This study investigates the bulk heterojunction structure of organic photovoltaic (OPV) devices using PM6 as the donor and Y6 as the non-fullerene acceptor. To visualize the donor–acceptor phase separation, differential phase contrast scanning transmission electron microscopy (DPC STEM) was used. This technique maps local electric fields and reconstructs electrostatic potential images, offering significantly higher contrast than conventional TEM, enabling clear visualization of organic material structures. Additionally, time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray absorption fine structure (XAFS) analysis were used to evaluate depth profiles and molecular orientation, respectively. Thin films were prepared by spin-coating PM6:Y6 solutions using either chloroform (CF) or dichlorobenzene (DCB) as solvents. DPC STEM revealed distinct phase separation in both samples, with larger domain sizes observed in DCB-based films. TOF-SIMS showed uniform vertical distribution in CF samples, while DCB samples exhibited non-uniformity. XAFS indicated molecular orientation only in DCB samples. These differences are attributed to the varying evaporation rates of the solvents, affecting the kinetics of phase separation and molecular ordering.