Enhanced efficiency of inverted bulk heterojunction solar cells with embedded silica nanoparticles

Incorporation of nanoparticles in the active layer is one of the possible approaches to improve the efficiency of bulk heterojunction organic solar cells (BHJ OSCs). Here, we have synthesized silica nanoparticles (SiO
₂
NPs) using the modified stober method and studied the dispersion of various concentrations of SiO
₂
NPs in poly (3-hexylthiophene), [6, 6]-phenyl C
₆₁
-butyric acid methyl ester (P3HT: PCBM) blend. It was found that the inverted geometry device with concentration of 2 wt% of SiO
₂
NPs and having the structure ITO/ZnO (NPs)/P3HT: PCBM: SiO
₂
NPs/MoO
₃
/Al shows a maximum efficiency of 1.95 %, which is more than 32 % larger compared to devices without SiO
₂
NPs. UV-Vis absorption measurements suggest that the incorporation of SiO
₂
NPs into a P3HT: PCBM blend improves the absorption. This absorption enhancement, supported also by finite difference time domain (FDTD) calculations of Mie scattering, results in the observed efficiency improvement.