•Preparation of TiO2 nanorod arrays with the length of 600 nm, diameter of 20 nm.•The compact PbS QD thin film and short-length TiO2 nanorod array were combined.•EDT addition improved PbS nanoparticle coverage and photovoltaic performance.•The compact PbS QD thin film sensitized solar cell achieved the PCE of 4.10%.Considering the balance of the hole diffusion length and the loading quantity of quantum-dots, the rutile TiO2 nanorod array with the length of 600 nm, the diameter of 20 nm, and the areal density of 500 μm−2 is successfully prepared by the hydrothermal method using the aqueous grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 °C for 105 min. The compact PbS quantum-dot thin film on the TiO2 nanorod array is firstly obtained by the spin-coating-assisted successive ionic layer absorption and reaction with using 1,2-ethanedithiol (EDT). The result reveals that the strong interaction between lead and EDT is very important to control the crystallite size of PbS quantum-dots and obtain the compact PbS quantum-dot thin film on the TiO2 nanorod array. The all solid-state sensitized solar cell with the combination of the short-length, high-density TiO2 nanorod array and the compact PbS quantum-dot thin film achieves the photoelectric conversion efficiency of 4.10%, along with an open-circuit voltage of 0.52 V, a short-circuit photocurrent density of 13.56 mA cm−2 and a fill factor of 0.58.The TiO2 nanorod array with the length of 600 nm, the diameter of 20 nm, the areal density of 500 μm−2 was successfully prepared. The compact PbS quantum-dot thin film was firstly obtained on the TiO2 nanorod array by spin-coating-assisted successive ionic layer absorption and reaction with using 1,2-ethanedithiol. The photoelectric conversion efficiency (PCE) of the compact PbS quantum-dot thin film sensitized solar cells achieved 4.10% using spiro-OMeTAD as a hole transporting layer, while the PCE of the PbS quantum-dot sensitized solar cells was only 0.54%.Download high-res image (113KB)Download full-size image

To improve the electron injection efficiency from PbS quantum dots to TiO2 nanorods and prevent the direct contact of spiro-OMeTAD and TiO2 nanorods, a compact PbS quantum-dot thin film can be successfully obtained on TiO2 nanorod arrays 360 nm in length by repeated spin coating of Pb(Ac)2, Na2S and 1,2-ethanedithiol solution in a step-by-step process. The corresponding solid-state quantum-dot-sensitized solar cells are fabricated using a novel structured FTO/compact PbS quantum-dot thin film sensitized TiO2 nanorod array/spiro-OMeTAD/Au that achieves a photoelectric conversion efficiency of 3.57% under AM 1.5 G illumination (100 mW cm−2), which represents a high value among all-solid-state PbS quantum-dot-sensitized TiO2 nanorod array solar cells.

•Preparation of TiO2 nanorod array with length of 70 nm and density of 1000 µm−2.•Influence of annealing temperatures on the -OH content of TiO2 nanorod arrays.•Preparation of over-500 nm-thickness CH3NH3PbI3−xBrx absorber layer.•Combination of short-length TiO2 nanorod array and high-thickness perovskite layer.•The best and average PCE with TiO2 array of 15.93% and 13.41±2.52% at 50–54% RH.The TiO2 nanorod arrays with the length of 70 nm, the diameter of 20 nm, and the areal density of 1000 µm−2 were firstly prepared by the hydrothermal method using the aqueous grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 °C for 60 min. Over-500 nm-thickness CH3NH3PbI3−xBrx absorber layers were successfully obtained by sequential deposition routes using 1.7 M PbI2·DMSO complex precursor solution and 0.465 M isopropanol solution of the methylammonium halide mixture with the molar ratio of CH3NH3I/CH3NH3Br=85/15. The perovskite solar cells based on the TiO2 nanorod array and 560 nm-thickness CH3NH3PbI3−xBrx absorber layer exhibited the best photoelectric conversion efficiency (PCE) of 15.93%, while the corresponding planar perovskite solar cells without the TiO2 nanorod array and with 530 nm-thickness CH3NH3PbI3−xBrx absorber layer gave the best PCE of 12.82% at the relative humidity of 50–54%.The TiO2 nanorod arrays with the length of 70 nm, the diameter of 20 nm, and the areal density of 1000 µm−2 were prepared by the hydrothermal method using the aqueous grown solution of 38 mM titanium isopropoxide and 6 M hydrochloric acid at 170 °C for 60 min. The optimal annealing temperature of TiO2 nanorod arrays was 450 °C. The perovskite solar cells based on the TiO2 nanorod array and 560 nm-thickness CH3NH3PbI3−xBrx absorber layer exhibited the best photoelectric conversion efficiency (PCE) of 15.93% and the average PCE of 13.41±2.52%, while the corresponding planar perovskite solar cells without the TiO2 nanorod array and with 530 nm-thickness CH3NH3PbI3−xBrx absorber layer gave the best PCE of 12.82% and the average PCE of 10.54±2.28% at the relative humidity of 50–54%.Download high-res image (307KB)Download full-size image