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Carbon-based counter electrodes of dye-sensitized solar cells (DSSCs) such as carbon black-graphite composite (CB/Gr) have received unprecedented interest in recent years due to their ease of fabrication, good corrosion resistance, and low cost compared to platinum (Pt) electrodes. However, the poor surface adherence between the carbon counter electrodes (CE) and FTO substrate, low surface area, and poor inter-particle connection between the carbon materials have consistently become a major challenge. In order to overcome these issues, we have fabricated CB/Gr by incorporating binders of titanium (IV) isopropoxide (TTIP), and zirconium (IV) dioxide (ZrO2) as the counter electrodes for the DSSC. The performance of the CE is characterized by four-point probe conductivity measurement, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and current density voltage (J-V) characteristics. The results revealed that incorporating binders to the CB/Gr has improved the series resistance (RS) and charge transfer resistance (RCT), which enhances the short-circuit current density (JSC), fill factor (FF), and the power conversion efficiency (PCE) of the device. The TTIP binder in CB/Gr CE exhibited superior performance in DSSC is largely attributed to the formation of TiO2 in situ with small particle size of about 100 nm, leading to enhanced intimate contact between the carbon materials, high surface area, and better surface adherence between counter electrode and the FTO substrate. Our findings, thereby, offer the possibility to engineer and optimize the energy levels of CE in an effort to develop a high-performing DSSC counter electrode.

In this work, we investigate how Al and Mg doped mesoporous TiO2 layers can improve the power conversion efficiency (PCE) of perovskite solar cells (PSCs) with respect to undoped mesoporous TiO2. The PSC configuration used in this study consists of mesoscopic structure with CH3NH3PbI3 as the perovskite absorber. A PSC with optimized mol% of Al and Mg doped mesoporous TiO2 layers has been shown to achieve up to 22% higher efficiency than that of pure TiO2. While the Mg doping only enhances the open-circuit voltage (VOC), the Al doping effectively enhances the VOC, the short-circuit current density (JSC), and the fill factor (FF). The occupancy of the doped metals in the lattice is confirmed by XRD, EDX, and XPS. The Mg doping increases the band gap of TiO2 while the Al doping decreases it. The wide band gap in Mg doped TiO2 reduces the electron and hole recombination rate, thus increasing the JSC and VOC. By Al doping, deep trap sites in the TiO2 are eliminated, and this effectively reduces the recombination losses and in turn, increases the JSC. The enhanced electron-hole generation rate attributed to the decrease in the band gap of Al doped TiO2 also increases the JSC. In addition, there is an enhancement on the electron mobility by the presence of Al metal and this gives an increase in the FF. The results have demonstrated the possibility of improving the PCE of PSCs by fine tuning the band gap of mesoporous TiO2.

We have computationally designed and characterized a series of new organic D−π−A architected dyes that have originated from cyanidin, which is vastly available in nature, for effective sensitization of DSSCs with absorption spectra extending up to near infrared region. Cyanidin acts as the donor group while cyanoacrylic acid and thieno [3, 2-b] thiophene are employed as the acceptor and π-spacer, respectively. Sensitization performance, depending on the substituted position of the π-spacer-acceptor (π-A) combination on cyanidin molecule, is examined by the results of density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The calculated data of free energy change driving force ( Δ G inject ), electron regeneration driving force ( Δ G regen ), open circuit potential eV OC and light harvesting efficiency (LHE) suggest two preferred substitutions of π-A combination to cyanidin molecule that leads to an efficient DSSC. At LUMO the designed sensitizers have denser electron cloud towards acceptor group that leads to an efficient electron injection process. All π-A substitutions resulted a broader absorption spectrum with a redshift up to 2500 nm which is a significant improvement compared to the vast majority of reported sensitizers.

Doping is a method whereby small amounts of impurities are introduced into the lattice of a material and is employed for improving the efficiency of dye-sensitized solar cells (DSSCs) via modification of the semiconductor material. Co-doping, which involves doping with more than one type of impurity, is typically used over doping owing to its unique effects on the short-circuit current and open-circuit voltage; the different types of added impurities can exert a synergy effect in enhancing the performance of DSSCs. Of particular interest is the study of the effects of the ionic radii of co-dopants on the performance of DSSCs that is not well understood to date. Thus, in this paper, TiO 2 was co-doped with lanthanum and magnesium, calcium, or aluminium at respective contents of 0.5 mol%. The co-doped TiO 2 and pure TiO 2 powders were prepared by sol–gel. Mg-La co-doped TiO 2 -based DSSC displayed the highest efficiency ( i.e. , 6.60%) and Al-La co-doped TiO 2 -based DSSC displayed the lowest efficiency. Among the dopants studied herein, aluminium ion has the smallest ionic radius. Thus, aluminium ions could easily enter the lattice structure of TiO 2 , generating a high concentration of holes that led to the decrease of electron transport and photocurrent, hence lower DSSC efficiency.

An improvement in the efficiency of Ixora ( Ixora sp. (Rubiaceae)) floral dye sensitized solar cells (DSSCs) has been achieved by diminishing the pigment’s interactions. Liquid column chromatography (LCC) separated the dye components, namely aurone, pelargonidin, and derivatives of cyanidin & malvidin, showed improved photovoltaic performance when compared to cells sensitized by the original dye extract of Ixora. The LCC separated dye components were analyzed using UV–Vis, fluorescence and Fourier transform infrared (FTIR) spectroscopic studies. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and band gaps of the dyes were investigated. The DSSC prepared with the LCC separated dye showed energy conversion efficiencies (ECEs) ranging from 0.203% to 0.951%, whereas the original Ixora dye sensitized cell showed an ECE of 0.381%. Transient photovoltage (TPV) measurements and electrochemical impedance spectroscopy (EIS) were used to elucidate the photovoltaic parameters.