Preparation Of Compact PbS Quantum-dot Thin Films And Tin Sulfide Thin Films And Their Application In Solar Cells

As important Ⅳ-Ⅵ semiconductor, PbS and tin sulfide have a good good application in solar cell. In this thesis, The compact PbS quantum-dot thin film was successfully prepared by the combination of TiO₂ nanorod arrays and using 1,2-ethanedithiol（EDT） in the procedure of the spin-coating-assisted successive ionic layer absorption and reaction（SILAR）. The solar cells with the novel structure of FTO/compact PbS quantum-dot thin film sensitized TiO₂ nanorod arrays/spiro-OMeTAD/Au were assembled. The PbS quantum-dot thin film sensitized TiO₂ nanorod array was obtained by the spin-coating-assisted SILAR. The influence of the spin-coating-assisted SILAR cycle times and the EDT introduce on the deposition process of PbS QD was evaluated. The compact PbS quantum-dot thin film on the TiO₂ nanorod array with different microstructure was obtained by the spin-coating-assisted SILAR. The influence of the microstructure of TiO₂ nanorod array on the photovoltaic performance of all solid-state compact PbS quantum-dot thin film sensitized solar cells was evaluated. TiO₂ nanorod arrays were successfully prepared on TiO₂ compact layers by the hydrothermal method using titanium isopropoxide as titanium source at 170 ℃.SnS and SnS₂ thin films were prepared by spin-coating-pyrolysis method using the methanol solution containing SnCl₂·2H₂O, SnCl₄·5H₂0 and thiourea as the precursor solution. The chemical composition,crystal structure, optical property and surface morphology of the SnS and SnS₂ thin films prepared at different pyrolysis temperature was investigated.The results revealed that 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 at 170 ℃ for 105 min. The deposition process of PbS QDs on the TiO₂ nanorod array with using EDT was obviously different from that without using EDT. the PbS QD were tightly connected together to form the compact and fully-covering PbS QD thin film with using EDT（the spin-coating-assisted SILAR cycle times of 20）, and the average crystallite size of PbS QDs was 7.8 nm. corresponding solid-state PbS QD thin film sensitized solar cells achieved the photoelectric conversion efficiency （PCE） of 4.10%. The crystallite sizes of the PbS QD on the surface of TiO₂ nanorod array deposited at the spin-coating-assisted SILAR cycle times of 10, 20, 30 were 10.9 nm, 12.9 nm and 15.0 nm. And corresponding solid-state PbS QDs thin film sensitized solar cells achieved the PCE of 0.77%, 0.54% and 0.23%, respectively. The length, diameter and areal density of Ti02 nanorod arrays with the growth time of 75 min, 100 min and 120 min were 290 nm, 15 nm and 710 μm-2, 540 nm, 20 nm and 530μm-2, 1040 nm, 24 nm and 300 μm-2. the average crystal sizes of PbS QDs prepared on TiO₂ nanorod arrays with the lengths of 290 nm, 540 nm and 1040 nm were all 7.8 nm.The corresponding solar cells with the TiO₂ nanorod array length of 290 nm, 540 nm,1040 nm achieved PCE of 2.02%, 4.81% and 1.95%, respectively. The appropriate pyrolysis temperature and time were 320 ℃, 10 min of SnS and 260℃, 2min of SnS₂.The atomic ratios of Sn/S for SnS thin films was 1:0.99, the prepared SnS thin films with the sheet-appearance were well crystallized. The atomic ratios of Sn/S for for SnS₂ and were 1:1.98, the prepared SnS₂ thin films with good crystallinity were uniform and porous.