The Study of Crystallization of Polyfluorene and Fullerene Derivatives in Semiconducting Layer of Organic Solar Cells

摘要

This research was focused on the effect of solid crystallization additive namely 1,4-dichlorobenzene (PDCB) in the 1:2 (w/w) active layer of benzothiadiazole/thiophene-based copolymers (PFTBzTT) to [6,6]-phenyl-C_(61) butyric acid methyl ester (PCBM) on the morphology and performance of bulk heterojunction (BHJ) organic solar cells. The active layer was deposited by spin-coating with chloroform solutions by different PDCB additive concentrations from 0-52 mg/ml. The inclusion of additive into the polymer solution was able to improve the performance of BHJ solar cells. The maximum power conversion efficiency (PCE) of 0.84% achieved for a cell with PDCB concentration of 36 mg/ml after annealing at 180 °C for 20 min. The XRD and TEM techniques used to analyse the crystal structure and morphology of the thin films. From these results were found that PDCB additive presented higher level of PCBM crystal structure by more aggregation of PCBM and a larger extent of phase separation than those of the films without additive. The AFM results demonstrated that the optimum PDCB concentration and annealing process helped PCBM aggregated into micron sized crystal rods.