Summary
Dye-sensitized solar cell (DSSC) attracts immense interest in the last few decades due to its various attractive features such as low production cost, ease of fabrication and relatively high conversion efficiency, which make it a strong competitor to the conventional silicon-based solar cell. In DSSC, photo-anode performs two important functions, viz. governs the collection and transportation of photo-excited electrons from dye to external circuit as well as acts as a scaffold layer for dye adsorption. The photo-anode usually consists of wide band gap semiconducting metal oxides such as titanium dioxide (TiO2) and zinc oxide (ZnO) deposited on the transparent conducting oxide substrates. The morphology and composition of the semiconductor oxides have significant impact on the DSSC photovoltaic performance. Therefore, enormous research efforts have been undertaken to investigate the influences of photo-anode modifications on DSSC performance. The modifications can be classified into three categories, namely interfacial modification through the introduction of blocking and scattering layer, doping with non-metallic anions and metallic cations and replacing the conventional mesoporous semiconducting metal oxide films with one-dimensional or two-dimensional nanostructures. In the present review, the previously mentioned modifications on photo-anode are summarized based on the recent findings, with particular emphasis given to published works for the past 5 years. Copyright © 2017 John Wiley & Sons, Ltd.

Recent advances in photo‐anode for dye‐sensitized solar cells: a review

Compared with crystallized TiO2, amorphous Nb2O5 has been applied in planar perovskite solar cell as electron transportation layer because of its excellent optical transmittance, low temperature preparation process, and similar Femi level with TiO2. However, the electron transfer rate is still limited by its low electron mobility and surface defect via room-temperature deposition process. Herein, a novel double buffer layer of [6,6]-phenyl-C61- butyric acid methyl ester(PCBM)/ionic liquid([EMIM]PF6) has been inserted between perovskite and Nb2O5 film. The PCBM could passive the surface of Nb2O5 and improve electron extraction ability. The insert of [EMIM]PF6 could improve the hydrophilic of PCBM and decrease the dissolution of PCBM in DMF during spin-coat perovskite precursor solution. A relatively high open voltage (over 1.09 V) and conversion efficiency of 18.8% have been achieved by using a double buffer layer which is the highest PCE of Nb2O5 based perovskite solar cell to our best knowledge. The resu...

Interface Modification for Planar Perovskite Solar Cell Using Room-Temperature Deposited Nb2O5 as Electron Transportation Layer

Enhanced performance of carbon-based planar CsPbBr3 perovskite solar cells with room-temperature sputtered Nb2O5 electron transport layer

The power conversion efficiency (PCE) of TiO2-based dye-sensitized solar cells (DSSCs) could be enhanced by modification of photoanodes. The effective blocking layer addition, one-dimensional nanostructure architecture, and scattering material design are the most important approaches to provide the high PCE of DSSCs and are critically reviewed in this work. The blocking layer generated the energy barrier can suppress the recombination of an electron in photoanode. One-dimensional (1D) nanostructures of a nanorod, nanotube and nanowire, promote the enhanced electron transport of DSSCs. The PCE of 1D nanostructure based DSSCs can potentially be improved by incorporating high surface area TiO2 nanoparticles and constructing the multilayered 1D nanostructure arrays photoanodes. The scattering effect can be generated by mesoporous, core-shell and yolk-shell materials with the sizes architecture corresponding to the wavelength of incident light, enhancing the light harvesting. The high efficiency of TiO2-based photoanodes could be realized by optimizing the composition, size of materials, and thickness of photoanodes.

The way forward for the modification of dye-sensitized solar cell towards better power conversion efficiency

CdO nanonecklace: Effect of air annealing on performance of photo electrochemical cell

The prevention of back electron transfer by inserting an energy barrier layer at the interface of a photo-anode is an effective method for improving the photovoltaic parameters in dye sensitised solar cells (DSSCs). In this study, phase a modified Nb2O5 blocking layer was inserted at the fluorine doped tin oxide (FTO)/TiO2 interface via a Rf magnetron sputtering process. For a critical tunnelling distance of ∼40 nm, the crystalline Nb2O5 blocking layer improved the efficiency close to 7% and outperformed the amorphous blocking layer by about 68%. The longer electron lifetime observed in DSSCs containing an inhomogeneous Nb2O5 layer indicates that trapping/de-trapping impedes the discharge of electrons to the TiO2 band edge. The origin of the longer electron lifetime is explained by formulating a theory from photovoltage decay measurements.

Chandrasekharan Nair Omanaamma Sreekala

Papers

The role of crystallinity of the Nb2O5 blocking layer on the performance of dye-sensitized solar cells