In this see more study, a facile, two-step wet chemical synthesis process at low temperature was applied to vertically grown TiO2 nano-branched arrays on F:SnO2 conductive glass (FTO). By varying the growth time, the length of nanobranches was optimized to provide a larger area for deposition of CdS quantum dots. Using the successive ionic layer adsorption and reaction (SILAR) method, CdS quantum dots were deposited on the surface of TiO2 nano-branched arrays to make a photoanode for quantum dot solar cells. The efficiency of the solar cells varied as the growth time of TiO2 nanobranches changed. A light-to-electricity conversion efficiency of 0.95% was recorded for

solar cells based on an optimized nano-branched array, indicating an increase of 138% compared to that of solar cells based on unbranched arrays. Methods Growth of single-crystalline rutile TiO2 nano-branched arrays by facile, two-step wet chemical synthesis process The TiO2 nanorod arrays were obtained using the following hydrothermal methods: 50 mL of deionized water was mixed with 40 mL of concentrated hydrochloric acid. After stirring at ambient temperature for 5 min, 400 μL of titanium tetrachloride was added to the

mixture. SRT1720 order The feedstock prepared above was injected into a stainless steel autoclave with a Teflon lining. The FTO substrates were ultrasonically cleaned for 10 min in a mixed solution of deionized water, acetone, and 2-propanol with volume ratios of 1:1:1 and were placed at an angle against the Teflon liner wall with the conducting side facing down. The hydrothermal synthesis was performed by placing the autoclave in an oven and keeping it at 180°C for 2 h. After synthesis, the autoclave was cooled to room temperature under flowing water, and the FTO substrates were taken out, washed extensively with deionized water, and dried in the open air. The TiO2

nanobranches were grown by immersing the TiO2 nanorod arrays PFKL prepared above in a bottle filled with an aqueous solution of 0.2 M TiCl4. The bottle was sealed and kept at a constant temperature of 25°C for 6 to 24 h. Finally, the TiO2 nano-branched arrays on FTO were rinsed with ethanol and air-dried at 50°C. After synthesis, the nano-branched arrays were annealed under 450°C for 30 min. Deposition of CdS quantum dots using successive ionic layer adsorption and reaction method In a typical SILAR deposition cycle, Cd2+ ions were deposited from a 0.05 M Cd(NO3)2 ethanol solution; the sulfide source was 0.05 M Na2S in methanol/water (1:1, v/v). The conductive FTO glass, pre-grown with TiO2 nano-branched arrays, was dipped into the Cd(NO3)2 ethanol solution for 2 min, then dipped into a Na2S solution for another 5 min. This entire SILAR process was repeated to obtain the optimal thickness of CdS quantum dots.