Ultrathin ALD coating on TiO2 photoanodes with enhanced quantum dot loading and charge collection in quantum dots sensitized solar cells

Abstract

TiO2 nanocrystals are widely used in photoanodes for quantum dot solar cells (QDSCs) owing to their chemical stability and suitable energy band structure. However, surface defects and grain boundaries of TiO2 nanocrystals photoanodes allow high surface charge recombination, which limits the performance of QDSCs. In this work, an ultrathin TiO2 layer is introduced to the surface of TiO2 photoanodes by atomic layer deposition (ALD). The ultrathin layer not only reduces the surface defects of TiO2 nanoparticles and strengthens the connection between adjacent nanoparticles to suppress the charge recombination for improving the electron collection efficiency (ηcc), but also increases the surface energy of photoanodes to load more quantum dots (QDs) for enhancing the light harvesting efficiency (LHE). As a result, the solar cell based on CdS/CdSe QDs with ALD treatment exhibits an efficiency of 5.07% that is much higher than that of the cells without modification (4.03%).

Controlled growth of Cu3Se2 nanosheets array counter electrode for quantum dots sensitized solar cell through ion exchange

“…4b shows that the internal photo-to-current efficiency spectrum (IPCE) of the solar cells investigated the changes in Jsc. The IPCE value of Cu3Se2 based solar cell was increased on the full light harvesting ranges of CdS/CdSe quantum dots [39], from 300 to 687 nm. The integral current density was improved from 9.02 to 10.21 mA cm −2 [40], which was basically matched with the Jsc.…”

Enhanced light harvesting and electron collection in quantum dot sensitized solar cells by TiO2 passivation on ZnO nanorod arrays

“…It is known that the driving force for electron injection from QDs to the ZnO conduction band is determined by the Fermi level between ZnO and QDs [8]. Here, the enhancement of the Voc indicates the upward of the Fermi level of ZnO/QDs, which leads to a decreased electron injection driving force, and thereby, a reduced Φinj is obtained [34]. Thus, we can conclude that the enhancement in ηcc owing to the incorporation of TiO2 helps to improve Jsc.…”

“…The effect of TiO2 NPs modification on the dynamic processes of electron transport and recombination of QDSCs was investigated in our study by IMPS and EIS [34,36]. As discussed above, the performance of the solar cells based on ZnO NAs decorated with TiO2 NPs is superior to the performance of those without TiO2 NPs modification.…”

Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the synergetic effect of NaYF4:Er3+/Yb3+ and g-C3N4

“…In particular, the properties of materials such as excellent light scattering, fast electron transport and large specific surface area play an important role in enhancing the light conversion efficiency of DSSCs [9,10]. In order to enhance the photoelectric conversion efficiency of a DSSC, researchers have designed different architectures of TiO2 nanocrystalline films, such as doping of metal and nonmetal elements, surface modifications, and combination with narrow band gap semiconductors [11][12][13]. In addition, the conduction and valence bands of the rare earth (RE) ion modified TiO2 nanoparticles have higher potentials than those of unmodified TiO2 nanoparticles due to the participation of RE ions in the hybridization orbital of TiO2, which can reduce the probability of recombination of excited electrons and holes to increase the short-circuit current during the operation of the DSSCs.…”