Microwave-assisted sol-gel synthesis of P3HT-ZnO: Sm3+, Yb3+: Study of structure, morphology, optical and electrical conductivity for organic solar cells application

Abstract

ZnO nanorods were synthesized using microwave-assisted sol-gel method. 1-Thioglycerol (TG) was used as a capping agent during the synthesis process. XRD results revealed that ZnO nanorods have hexagonal wurtzite structure despite being capped or doped. UV–Vis and PL showed that ZnO nanorods capped with 0.2 M concentration of TG have the highest absorption efficiency and emission intensity, respectively. Upon doping with samarium (Sm3+) and ytterbium (Yb3+), ZnO:3% Sm3+, 5% Yb3+ sample had the highest PL intensity. Therefore, this sample was incorporated into pristine poly(3-hexylthiophene) (P3HT)-conjugated polymer and systematically the effects on the structure, morphology, optical and electrical conductivity were investigated. The PL intensity was significantly quenched by the sample P3HT-ZnO:3% Sm3+, 5% Yb3+ at the ratio of 1:5 (P3HT: ZnO), indicating a charge transfer between donor and acceptor materials. FESEM showed the transformation of morphology from nanoflakes (uncapped ZnO) to nanorods (0.2 TG capped). XPS showed a shift to higher binding energy which may be due to the presence of absorbed light or moisture from the atmosphere. FTIR confirmed the ZnO and P3HT vibration modes and current-voltage (I–V) measurements showed an improved electrical conductivity for P3HT-ZnO:3% Sm3+, 5% Yb3+ (1:5).