Ni‐doped TiO ₂ / TiO ₂ homojunction photoanodes for efficient dye‐sensitized solar cells

Abstract

The development of novel bilayer photoanodes plays an essential role in dyesensitized solar cell (DSSC) applications to fabricate efficient devices. Herein, a novel homojunction photoanode consisting of undoped and Ni-doped TiO 2 layers with trace amounts of Ni dopant (0.5% at.) was prepared. After a systematic study on photoconversion efficiency that changes with tuning the location of the doped layer, an in-depth understanding was obtained regarding the physical mechanism of the coupling of structural, optical and electrical properties. We demonstrated that the doped layer can be utilized for highperformance DSSCs by employing a homojunction photoanode consisting of an upper-layer of Ni-doped TiO 2 and a lower-layer of undoped TiO 2 to dramatically increase the photoconversion efficiency. We monitored that the light absorption ability of the dye-loaded photoanodes strongly improved with the bilayer (Ni-doped TiO 2 /TiO 2 ), leading to a higher short circuit current. From impedance spectroscopy (Mott-Schottky plots), compared to both undoped and the doped single-layer analogues, a greater shift to more negative flat band potential was noticed for the bilayer and, therefore, a higher open-circuit voltage was achieved. From electrochemical impedance spectroscopy analysis, it was found that chemical capacitance decreases, while recombination resistance increases after Ni incorporation in the photoanode. They were associated with a reduction in the number of immobile electrons trapped by defect states. A relatively longer electron lifetime of 10.18 ms and diffusion length of 63.2 μ m were obtained for the device assembled with the homojunction (Ni-doped TiO 2 /TiO 2 ). The PCE (6.08%) of the device assembled with the bilayer was superior to its single-layer analogue (4.13%), owing to its enhanced light harvesting capability, proper band alignment, improved injection ability, fast electron transport and better collection efficiency. Our results shed light on important characteristics of a homojunction photoanode, which can be considered for future studies and applications.

A Joint Theoretical and Experimental Study on a Tetrazole‐Anchored BODIPY‐Based Dye at the Surface of TiO2 for Dye‐Sensitized Solar Cell Applications

“…The series contact resistance indicated by R s , the charge‐transfer resistance between the counter electrode and the TiO 2 indicated by R 1 , and the resistance value of the TiO 2 /dye/electrolyte indicated by R 2 in the equivalent model are all shown at the initial point of the intercepts with the real axis. [ 70,71 ] The R s values almost remain the same. As shown in Table 6 , the R 1 value for the BODIPY‐loaded device of 85.9 Ω is greater compared to N719 of 6.1 Ω.…”

“…[ 72 ] A relatively higher value of HOMO level of the present dye guarantees a larger value of driving force for dye generation. [ 68–71 ] Even though the difference between LUMO level and E c of TiO 2 is appreciable for the dye, J sc value stays behind that of other dyes. [ 68–71 ] This might be attributed to weak light absorption ability of the dye.…”

“…[ 68–71 ] Even though the difference between LUMO level and E c of TiO 2 is appreciable for the dye, J sc value stays behind that of other dyes. [ 68–71 ] This might be attributed to weak light absorption ability of the dye. V oc is also associated with energy level of electrolyte.…”

Mechanistic Understanding in Manipulating Energetics of TiO2 for Photocatalysis

“…One way to further boost the photoelectrochemical performance of doped TiO 2 is to produce heterojunction between doped and undoped TiO 2 , which was demonstrated to suppress charge recombination rate and provide fast charge transport for Ni-doped TiO 2 . 206 A composite catalyst of Cu 3 Pg-C 3 N 4 nano-heterojunctions 207 with TiO 2 can produce synergistic effects in photocatalytic H 2 generation. Multilayer p-n and n-n heterojunctions are effective methods to enhance photocatalysis, as they have built-in electric and/or magnetic fields.…”

Experimental investigation of spin coating acceleration effect on the DSSC performance

“…These structures are given as photoanode (PA) coated with a mesoporous TiO 2 nanoparticles, a molecular dye that absorbs the sunlight, electrolyte solution that creates a conducive atmosphere for the movement of electrons and a counter electrode (CE) which is platinum coated catalyst. Given that, a great deal of investigation has been done on each component/layer independently to enhance the DSSCs' performance metrics [4]. The component of a DSSC that really determines how effectively light is harvested is called a dye sensitizer.…”