A binary hybrid composite of g-C3N4 and ZnO is introduced as a photoanodic material in QDSSC devices and ∼70% improvement in power conversion efficiency is achieved.
Hexagon shaped mesoporous zinc oxide nanodisks (ZnO NDs) with exposed ±{0001} polar facets have been synthesized by using ethyl cellulose (EC) and cetrimonium bromide (CTAB) as the capping and structure directing agents. We have characterized ZnO NDs using analytical techniques, such as powder X-ray diffraction (PXRD), diffuse reflectance UV-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analysis and proposed a plausible mechanism for the formation of ZnO NDs. EC molecules form a colloidal solution in a 1-butanol:water (3:1) solvent system having a negative zeta potential (ζ ≈ -32 mV) value which can inhibit CTAB assisted c-axis growth of ZnO crystal and encourage the formation of ZnO NDs. In the control reactions carried out in presence of only CTAB and only EC, formation of hexagonal ZnO nanorods (NRs) and ZnO nanosheets (NSs) composed of numerous ZnO nanoparticles are observed, respectively. Photovoltaic properties of ZnO NDs as compared to ZnO NRs, ZnO NSs, and conventional ZnO nanoparticles (NPs) are investigated by co-sensitizing with CdS/CdSe quantum dots (QDs). An ∼35% increase in power conversion efficiency (PCE, η) is observed in ZnO NDs (η ≈ 4.86%) as compared to ZnO NPs (η ≈ 3.14%) while the values of PCE for ZnO NR and ZnO NS based devices are found to be ∼2.52% and ∼1.64%, respectively. Enhanced photovoltaic performance of the ZnO NDs based solar cell is attributed to an efficient charge separation and collection, boosted by the exposed ±(0001) facets apart from the single crystalline nature, better light-scattering effects, and high BET surface area for sensitizer particle adsorption. Electrochemical impedance spectroscopy (EIS) analysis further reveals that the charge recombination resistance and photoinduced electron lifetime are substantially higher in the ZnO ND based device than in ZnO NR, ZnO NP, and ZnO NS based devices, which demonstrates a slower electron-hole (e(-)-h(+)) recombination rate and faster charge migration through the single crystalline ZnO NDs.
Herein, we report a power conversion efficiency of 3.71% using mesoporous SnO2 in combination with 2D MgO nanosheets, sensitized by a metal free carbazole dye.
Finding
the material characteristics satisfying most of the photovoltaic
conditions is difficult. In contrast, utilization of foreign materials
that can contribute to light harvesting and charge transfers in the
devices is now desirable/thought-provoking. Herein, a binary hybrid
photoanode utilizing nano-amassed micron-sized mesoporous zinc oxide
hollow spheres (meso-ZnO HS) in conjunction with SnO
2
nanoparticles
(NPs), i.e., SnO
2
NP_ZnO HS (for an optimized weight ratio
(8:2)), displayed a nearly ∼4-fold increase in the efficiency
(η) compared to that of bare SnO
2
nanoparticle device.
Enhanced device efficacy in the composite photoanode-based device
can be accredited to the dual function of nano-amassed meso-ZnO HS.
Nano-amassed micron-sized ZnO HS embedded in the photoanode can increase
the light-harnessing capability without sacrificing the surface area
as well as optical confinement of light by multiple reflections within
its cavity and enhanced light-scattering effects. Electrochemical
impedance spectroscopy analysis revealed an extended lifetime of electron
(τ
e
) and a higher value of
R
ct2
at the working electrode/dye/redox mediator interface,
indicating a minimum photoinduced electron interception. The open-circuit
voltage decay reveals a slower recombination kinetics of photogenerated
electrons, supporting our claim that the nano-ammased meso-ZnO HS
can serve as an energy barrier to the photoinjected electrons to retard
the back-transfer to the electrolyte. Moreover, the improvement in
the fill factors of the composite-based devices is endorsed to the
facile penetration of the electrolyte through the pores of nano-amassed
meso-ZnO HS, which increases the regeneration probability of oxidized
dyes.
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