This paper presents a novel water-based ZnO precursor stabilized with labile NH3, which allows the spinning of coat crystalline ZnO thin films at a temperature below 200 oC. Thin film transistors (TFTs) and diode-type quantum dot solar cells (QD SCs) were fabricated with ZnO as electron conduction layer. In the QD SCs, a p-type 1,2-ethylenedithiol treated PbS QDs with a bandgap of eV, was spin-coated on top of ZnO layer by a layer-by-layer solid state ligand exchange process. | VNU Journal of Science: Natural Sciences and Technology, Vol. 34, No. 3 (2018) 116-122 Low-Temperature ZnO Thin Film and Its Application in PbS Quantum Dot Solar Cells Mai Xuan Dzung1,*, Hoang Quang Bac1, Dinh Thi Cham1, Le Quang Trung1, Nguyen Trong Tung2, Duong Ngoc Huyen2, Mai Van Tuan2,3, Le Dinh Trong4 1 Department of Chemistry, Hanoi Pedagogical University 2, 32 Nguyen Van Linh, Phuc Yen, Vinh Phuc 2 School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi 3 Faculty of Natural Sciences, Electric Power University, 235 Hoang Quoc Viet, Hanoi 4 Department of Physics, Hanoi Pedagogical University 2, 32 Nguyen Van Linh, Phuc Yen, Vinh Phuc Received 04 October 2017 Revised 10 September 2018; Accepted 10 September 2018 Abstract: Zinc oxide (ZnO) has been widely deployed as electron conducting layer in emerging photovoltaics including quantum dot, perovskite and organic solar cells. Reducing the curing temperature of ZnO layer to below 200 oC is an essential requirement to reduce the cell fabrication cost enabled by large-scale processes such as ink-jet printing, spin coating or roll-roll printing. This paper presents a novel water-based ZnO precursor stabilized with labile NH3, which allows the spinning of coat crystalline ZnO thin films at a temperature below 200 oC. Thin film transistors (TFTs) and diode-type quantum dot solar cells (QD SCs) were fabricated with ZnO as electron conduction layer. In the QD SCs, a p-type 1,2-ethylenedithiol treated PbS QDs with a bandgap of eV, was spin-coated on top of ZnO layer by a layer-by-layer solid state ligand exchange process. Electron mobility of ZnO was about cm2V-1s-1 as determined from TFT measurements. Power conversion efficiency of solar cells: FTO/ZnO/PbS/Au-Ag was under irradiation conditions. The possibility of deposition of ZnO at low temperatures plays an important role in producing low-cost electronic and optoelectronic devices. Keywords: ZnO, .