Effect of Various Structures on the Efficiency of Organic Solar Cells

Small molecule organic solar cell with an optimized structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (10nm)/CuPc: C60 mixed (20nm)/fullerene (C60) (20nm)/bathocuproine (BCP) (10nm)/Al) was fabricated. With optimizing the hybrid planar-mixed molecular heterojunction (PM-HJ) from the double layer heterojunction (HJ) and the bulk heterojunction (BHJ), the short-circuit current density (Jsc) increased from 3.09 to 5.11mA/cm2, the open-circuit voltage (Voc) increased from 0.40 to 0.47V, and the power conversion efficiency (ηp) increased from 0.66 to 1.28% under 100mW/cm2 AM1.5G illumination. These improvements were attributed to reach the optimal balance among the light absorption efficiency, the exciton dissociation efficiency and the carrier collection efficiency of the device, resulting in enhancement of Jsc without affecting the value of fill factor (FF) and the reduction of the dark current. Furthermore a decrease of dark current is caused to the higher Voc.