200-nm long TiO2 nanorod arrays for efficient solid-state PbS quantum dot-sensitized solar cells

To ensure the infiltration of spiro-OMeTAD into the quantum dot-sensitized photoanode and to consider the limit of the hole diffusion length in the spiro-OMeTAD layer, a rutile TiO2 nanorod array with a length of 200 nm, a diameter of 20 nm and an areal density of 720 mu m(-2) was successfully prepared using a hydrothermal method with an aqueous-grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 degrees C for 75 min. PbS quantum dots were deposited by a spin coating-assisted successive ionic layer adsorption and reaction (spin-SILAR), and all solid-state PbS quantum dot-sensitized TiO2 nanorod array solar cells were fabricated using spiro-OMeTAD as electrolytes. The results revealed that the average crystal size of PbS quantum dots was similar to 7.8 nm using Pb(NO3)(2) as the lead source and remain unchanged with the increase of the number of spin-SILAR cycles. The all solid-state PbS quantum dot-sensitized TiO2 nanorod array solar cells with spin-SILAR cycle numbers of 20, 30 and 40 achieved the photoelectric conversion efficiencies of 3.74%, 4.12% and 3.11%, respectively, under AM 1.5 G illumination (100 mW/cm(2)). (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.