Abstract

Highly crystalline NiO_X usually requires high annealing temperature (>300 °C) which is incompatible with flexible substrate and might consume high amount of energy. Herein, we demonstrate a facile emulsion process to synthesize highly crystalline, low temperature deposition (<150 °C) and solution processable NiO_x nanoparticles (NPs) as a hole transport layer for the perovskite solar cells (PVSCs). A novel surfactant of tetramethylammonium hydroxide (TMAOH) was used to react with Ni(NO₃)₂ to form Ni(OH)₂ nanoparticles (NPs). The micelles of TMAOH act as a nano-reactor containing OH⁻ anion. The Ni⁺ cation enters into the nano-reactor to form Ni(OH)₂ NPs inside the reactor with controlled particle size. The Ni(OH)₂ NPs prepared by emulsion process are further calcined to form NiO_X NPs with the particle size of 8.28 ± 2.64 nm (EP-NiO_X). The smaller size of EP-NiO_X NPs results in a good dispersibility and an excellent stability of NPs suspension, which can be used to fabricate uniform NiO_X film without any aggregates. A power conversion efficiency (PCE) of 18.85% can be achieved using this EP-NiO_X film, as compared with 16.68% using the NiO_X NPs synthesized from the chemical precipitation method (CPM-NiO_X). Moreover, a flexible PVSCs with a PCE of 14.28% can be fabricated using the EP-NiO_X film. Except for the device performance, the quality of the EP-NiO_X film shows a good batch-to-batch uniformity, resulting in an excellent reproducibility of PVSCs. This work has a potential for the development of a large-scale production of PVSCs with a high energy conservation.

Citations

Authors (11)