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Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO2/quantum dot (QD) sensitizer/electrolyte. Hence, blocking or suppressing the charge recombination is an essential requirement to elevate the QDSSC performance to the next level. To retard the charge recombination, herein, we propose the introduction of a SnO2 nanograss (NG) interlayer on the surface of TiO2 using the facile chemical bath deposition method. The SnO2 NG interlayer not only inhibits the interfacial recombination processes in QDSSCs but also enhances the light-harvesting capability in generating more excitons. Hence, the TiO2/SnO2 NG/CdS QDSSCs can achieve the power conversion efficiency of 3.15%, which is superior to that of a TiO2/CdS device (2.16%). Electrochemical impedance spectroscopy, open-circuit voltage decay and dark current analyses confirm that the recombination of charges at the photoanode/electrolyte interface is suppressed and the life time is improved by introducing the SnO2 NG interlayer between the TiO2 and CdS QD sensitizer.

Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO

An ideal counter electrode (CE) that is cost-effective and has high electrocatalytic activity, high performance stability, and a simple fabrication process is essential for quantum dot-sensitized solar cells (QDSSCs). We report a facile one-step chemical bath deposition method for the growth of an L-cysteine-dependent CuxS thin film on a fluorine-doped tin oxide substrate, which was used as a highly efficient CE for QDSSCs. SEM images revealed that the surface morphology of CuxS changed from nanoplatelets to nanosheets to nanospheres to nanoflowers based on the concentration of L-cysteine. Also, the concentration of L-cysteine in the formation of CuxS thin films is expected to play an important role in determining the phase of CuxS thin films (Cu2S, Cu1.75S, Cu1.12S and CuS). QDSSCs based on Cu1.12S nanosphere CEs possess a high power conversion efficiency of 5.88%, which is much higher than those of QDSSCs based on Cu2S nanoplatelets (5.10%), Cu1.75S nanosheets (5.32%), CuS nanoflowers (4.88%) and Pt (1.36%) CEs. Electrochemical measurements revealed that a Cu1.12S nanosphere CE has better electrocatalytic activity, which increases the rate of reduction of polysulfide in comparison to those of Cu2S nanoplatelets, Cu1.75S nanosheets, CuS nanoflowers and Pt CEs. A QDSSC also displayed superior stability in an operational state for over 20 h, which is a major challenge for CuxS CEs.

Hierarchical flower-like ZnO@MnCo2O4 nanosheets and dandelion-like MnCo2O4 were synthesized on nickel foam using a facile and cost-effective hydrothermal approach combined with a short post-annealing treatment. The surface properties, crystalline phase, and electrochemical properties of the flower-like and dandelion-like electrodes were studied by field emission scanning electron microscopy, X-ray diffraction, cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy. The flower-like ZnO@MnCo2O4 nanosheet electrode exhibited high specific capacitance of 631.2 F g−1 and a high energy density of 56.10 W h kg−1 at a current density of 1 A g−1, which is higher than that of the dandelion-like MnCo2O4 electrode (452.5 F g−1). Impressively, as an electrode material for supercapacitors, the flower-like ZnO@MnCo2O4 also shows exceptional cycling performance over 1000 charge/discharge cycles, indicating good long-term cycling stability. These results highlight the unique ZnO@MnCo2O4 electrode as a promising electrode for energy storage applications in supercapacitors.

An ideal counter electrode (CE), with high-level electrocatalytic activity, high performance stability, and applicable fabrication simplicity, is significant to convey the advantages of quantum-dot-sensitized solar cells (QDSSCs). We report CuS nanoplatelets that are cohered on a conductive FTO substrate using an inexpensive and facile one-step low-temperature chemical bath deposition technique with different concentrations of acetic acid and can be employed as CE without any post-treatments for QDSSCs. The acetic acid affects the morphology, density of nanostructure, thickness, and Cu vacancies with increased S composition of CuS. The TiO2/CdS/CdSe/ZnS QDSSC with the optimized CuS CE under one sun illumination (AM 1.5G, 100 mW cm−2) exhibits an energy conversion efficiency (η) of 5.15%, which is higher than that of a platinum (Pt) CE (1.25%). This enhancement is mainly attributed to the optimized CuS nanostructure, which exhibits a lower charge transfer resistance (7.89 Ω) at the interface of the CE/electrolyte and superior electrochemical catalytic ability. A preliminary stability test reveals that the CuS CE exhibits good stability with no degradation for 20 h. Therefore, the easily prepared CuS is very promising as a stable and efficient CE for QDSSCs.

Here for the first time, we demonstrate a novel Mn-doped CuS counter electrode via a facile chemical bath deposition, which exhibited an efficiency of 5.46% comparable to the solar cell based on the bare CuS electrode (4.29%) and Pt electrode (1.37%) under similar conditions.

The performance of quantum dot-sensitized solar cells (QDSSC) is restricted due to the insufficient electrocatalytic activity and stability of counter electrodes (CEs), which are critical but challenging issues. The exploration of CE catalysts to match the redox couples has become a feasible route in the pursuit of high power conversion efficiency, stability, and reduction of fabrication costs. Electrodes were made by the deposition of a PbS thin film on a fluorine-doped tin oxide substrate at various growth times by a facile one-step chemical bath deposition approach. They were used as a highly catalytic CE without any post-treatments for QDSSCs filled with aqueous sulfide/polysulfide (S2−/Sn2−) electrolyte. The morphology, thickness, crystal structure, composition, and optical properties are dependent on the growth time of PbS and were characterized by SEM, XRD, XPS, EDS, and UV-vis analysis. In addition to surface morphology, the increase in the atomic ratio of S in PbS plays a key role in increasing the electrocatalytic activity of the CE. These PbS nano-cubes were used as an effective CE material in QDSSCs to show high electrocatalytic activity for catalyzing the reduction of the polysulfide electrolyte, which contributes to significant improvement in the short current density and fill factor. The QDSSC with the optimized PbS CE exhibits a power conversion efficiency of 4.61%, which is much higher than that of Pt CE (1.34%). Furthermore, this PbS CE shows high and consistent electrocatalytic activity toward polysulfide reduction, which was confirmed by electrochemical measurements. This leads to improved photovoltaic performance and superior stability of the QDSSC.