Effect of Crystallinity on the Performance of P3HT/PC70BM/n Dodecylthiol Polymer Solar Cells

Abstract

In this research, ndodecylthiol was added to P3HT/PC70BM polymer solar cells (PSCs) to improve the crystallinity of P3HT and enhance the phase separation of P3HT/PC70BM. Crystallinity of P3HT:PC70BM doped with 0–5% by volume of ndodecylthiol was measured using Xray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. Both methods showed improvement in crystallinity, which resulted in improving the power conversion efficiency (PCE) of polymer solar cells by 33%. In addition, annealing at 150 آ°C for 30 min showed further improvement in crystallinity with ndodecylthiol concentration up to 2%. The highest power conversion efficiency of 3.21% was achieved with polymer crystallites size L of 11.2 nm, after annealing at 150 آ°C for 30 min under a vacuum atmosphere. The smaller crystallite size suggests a shorter path of the charge carriers between P3HT backbones, which could be beneficial to getting a higher short circuit current in the devices made with the additive. Kinetics study of P3HT:PC70BM crystallinity using Avrami model showed a faster crystallization rate (1/t0.5) at higher temperatures.