Low-Temperature ZnO Thin Film and Its Application in PbS Quantum Dot Solar Cells

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 1.4 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 0.1 cm²V^-1s^-1 as determined from TFT measurements. Power conversion efficiency of solar cells: FTO/ZnO/PbS/Au-Ag was 3.0% under AM1.5 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, low-temperature, quantum dot solar cell, TFTs

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