Structural modification and conductivity enhancement of NiCl2 incorporated P3HT: PC60BM based organic photoactive layer

Abstract

High planar defect and poor crystalline structure in P3HT has limited the device performance of organic photovoltaic. To date, surface modification on the P3HT molecular structure has been introduced to improve its intrinsic properties. In this project, different volume percent of NiCl2 were incorporated into the P3HT:PC60BM film using a wet chemical approach. The effects on the structural, electrical, and optical properties of the active material after the metal halide incorporation were elucidated. Among the samples, 20 vol% NiCl2 sample presented the highest C–C intra-ring in raman analysis, which signifies the formation of long conjugate P3HT chain that contributes to a stronger electron phonon coupling and promotes a charge transfer from CC bonds. After the active layer was incorporated with 20 vol% NiCl2, the surface roughness of the film decreased from (13.8 ± 2.6) nm to (4.2 ± 1.5) nm as compared to pristine P3HT:PC60BM film. The photoabsorbance and electrical conductivity of 20 vol% NiCl2 sample also increased by 1.8 fold and 47%, respectively. The presence of NiCl2 can serve as a surface passivator in P3HT interface which eventually reduces the electron organisation energy and increases the charge transport ability in active layer. This novel finding can serve as an alternative to improve the device performance of P3HT-based active material organic solar cells.