An Alternative Route Towards Monodisperse CdS Quantum Dots For Solar Cells

Quantum dots (QDs) are becoming one kind of hot materials in the field of thefundamental and application research due to their good dispersion, high crystallization andsize dependent optical properties. Quantum dot based solar cells have drawn a lot ofattention because of the possibility of the power conversion efficiency beyond thetraditional Si based solar cells of28%. There are tons of reports regarding QDs’ syntheses.Nowadays, the typical state of the art methods for high quality QDs include theorganometallic approach, its alternative one pot approach, and some others, but the mostexperimentals of the above methods either contain poisonous solvents or employexpensiveoriginal materials.These obstruct the large-scale syntheses of QDs. Therefore, itis important to develop one environmentfriendly method to synthesize the large-scale QDswith low cost.Here, we attempt a benign solution approach to synthesize CdS QDs with large-scale.Meanwhile, as-obtained CdS QDs are applied in the hybrid solar cells as one example forthe synthese. The main achievements are listed as followings:1. We develop a green synthetic method using cost-effective commercial0#dieselas reaction solvent at200centigrade. In this approach, Cadmium oxide is used as Cdresource, S power as S resource, OA as the ligand. A strong absorption peak near325nm,which was attributed to magic-size nanoclusters(MSCs) of CdS as the reactionintermediaries, developed at an early stage of the synthesis of regular CdS QDs.2. MonodisperseCdS quantum dots (QDs) are synthesized by thermal decompositionof organic complexes. The prepared CdS QDs have a good dispersion and highcrystallization. After the CdS QDs are doped into poly(3-hexylthiophene)(P3HT) and1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61(PCBM) blends as an active layer forhybrid solar cells (HSCs), the HSCs achieve about25%increase of power conversionefficiency in comparison with no CdS QDs doping of the reference device, Jsc=7.23 mA/cm2, Voc=0.61V, FF=57%. The good cell performance is mainly attributed to theincreased short-circuit current density arising from the absorption enhancement in thewavelength range of350~550nm by introducing the synthesized CdS QDs into the P3HT:PCBM active layer.