Qamar Wali

Multiporous nanofibers of SnO2 by electrospinning for high efficiency dye-sensitized solar cells

Various one-dimensional nano-morphologies, such as multiporous nanofibers (MPNFs), porous nanofibers (PNFs), and nanowires (NWs) of SnO2, are synthesized using electrospinning technique by controlling the tin precursor concentration. The MPNFs have ∼8-fold higher surface area compared to the other morphologies. Dye-sensitized solar cells (DSCs) were fabricated using these nanostructures as photoanodes and their performance was compared. The MPNFs surpass the performance of PNFs and NWs as well as conventional TiO2 paste. Record photoconversion efficiency (PCE) of ∼7.4% was realized in MPNFs DSCs, which was twice to that achieved using PNFs (∼3.5%). Furthermore, the MPNFs showed over >80% incident photon to current conversion efficiency (22% higher than that achieved by spherical P25 TiO2 particles) and also demonstrated ∼3 times longer electron lifetime and electron diffusion length. Owing to the possibility to produce large quantities using electrospinning technique, huge commercial potential of SnO2 nanostructures, and promising results achieved herein, the MPNFs are expected soon to be utilized in commercial devices.

Mesoporous titania-vertical nanorod films with interfacial engineering for high performance dye-sensitized solar cells

Working electrode (WE) fabrication offers significant challenges in terms of achieving high-efficiency dye-sensitized solar cells (DSCs). We have combined the beneficial effects of vertical nanorods grown on conducting glass substrate for charge transport and mesoporous particles for dye loading and have achieved a high photoconversion efficiency of (η) > 11% with an internal quantum efficiency of ∼93% in electrode films of thickness ∼7 ± 0.5 μm. Controlling the interface between the vertical nanorods and the mesoporous film is a crucial step in attaining high η. We identify three parameters, viz., large surface area of nanoparticles, increased light scattering of the nanorod-nanoparticle layer, and superior charge transport of nanorods, that simultaneously contribute to the improved photovoltaic performance of the WE developed.

Probing Electron Lifetime and Recombination Dynamics in Large Area Dye-Sensitized Solar Cells by Electrochemical Impedance Spectroscopy

A number of nanocrystalline, mesoporous large area (~0.2- 2 cm2) dye-sensitized solar cells (DSSCs) are probed by electrochemical impedance spectroscopy measurements to realize their carrier dynamics such as charge transport resistance (RCT), electron diffusion coefficient (Dη), and electron lifetime (τn) by applying an equivalent electrical model. The experimental upshots reveal that the electron lifetime relates with the device physical parameters which was neglected in previous studies. It is also found that the RCT relates negatively with the device area i.e. it decrease upon increasing photo-exposed area. The observed lowering of current density (JSC) over a series of experiments upon increasing the photoelectrode area is attributed to the decrease in RCT. The charge carriers upon injection into semiconductor layer find increased diffusion pathways and eventually recombine with the hole species when characterized by lower carrier lifetime. The thickness of the electrode film does not play an effective role indicating that the dynamics of larger area DSSCs differs largely from those of a single cell. The experimental results available indicate that a nearly complete collection of charge carriers is possible in large area modules provided the physical dimensions of photoelectrode area are considered. The results from the study hints future directions to build high efficiency DSSC modules and further asserts considering the diffusion length in two-dimensions while fabricating larger area cells.

Data of chemical analysis and electrical properties of SnO 2 -TiO 2 composite nanofibers

In this data article, we provide energy dispersive X-ray spectroscopy (EDX) spectra of the electrospun composite (SnO2-TiO2) nanowires with the elemental values measured in atomic and weight%. The linear sweep voltammetry data of composite and its component nanofibers are provided. The data collected in this article is directly related to our research article “Synergistic combination of electronic and electrical properties of SnO2 and TiO2 in a single SnO2-TiO2 composite nanowire for dye-sensitized solar cells” [1].