Assemble of porous heterostructure thin film through CuS passivation for efficient electron transport in dye-sensitized solar cells

Three different modified solar cells have been passivated with copper sulfide (CuS) on a TiO2 electrode and manganese sulfide (γ-MnS) hexagonal as photon absorbers. The MnS were prepared using (a-c) bis(N-Piperl-N-p-anisildithiocarbamato)Manganese(II) Complexes Mn[N-Piper-N-p-Anisdtc] as (MnS_1), N-p-anisidinyldithiocarbamato Mn[N-p-anisdtc] as (MnS_2) and N-piperidinyldithiocarbamato Mn[N-piperdtc] as (MnS_3). The corresponding passivated films were denoted as CM-1, CM-2, and CM-3. The influence of passivation on the structural, optical, morphological, and photochemical properties of the prepared devices has been investigated. Raman spectra show that the combination of this heterostructure is triggered by the variation in particle size and surface effect, thus resulting in good electronic conductivity. The narrow band gaps could be attributed to good interaction between the passivative materials on the TiO2 surface. CM-2 cells, stability studies show that the cell is polarized and current flows due to electron migration across the electrolyte and interfaces at this steady state. The cyclic voltammetry (CV) curve for the CM-3 with the highest current density promotes the electrocatalytic activity of the assembled solar cell. The catalytic reactions are further confirmed by the interfacial electron lifetimes in the Bode plots and the impedance spectra. The current-voltage (J-V) analysis suggests that the electrons in the conduction band of TiO2/CuS recombine with the semiconductor quantum dots (QDs) and the iodolyte HI-30 electrolyte, resulting in 5.20-6.85% photo-conversions.

Improving the Conversion Ratio of QDSCs via the Passivation Effects of NiS

To revolutionize the photochemical efficiency of quantum dots sensitized solar cells (QDSSCs) devices, herein, a passivation of the cells with multilayer material has been developed for heterojunctions TiO2/NiS/MnS/HI-30/Pt devices. In this study, NiS and MnS were deposited on a photoanode for the first time as passivated photon absorbers at room temperature. The adoption of NiS as a passisvative layer could tailor the active surface area and improve the photochemical properties of the newly modified cells. The vibrational shifts obtained from the Raman spectra imply that the energy change is influenced by the surface effect, giving rise to better electronic conductivity. The electrochemical stability and durability test for the N/M-3 device slows down and remains at 8.88% of its initial current after 3500 s, as compared to the N/M-1 device at 7.20%. The disparity in charge recombination implies that both the outer and inner parts of the nanoporous material are involved in the photogeneration reaction. The hybridized N/M-3 cell device reveals the highest current density with a low potential onset, indicating that power conversion occurs more easily because photons tend to be adsorbed easily on the surface of the MnS. The Nyquist plot for N/M-1 and N/M-3 promotes the faster transport of electrolytic ions across the TiO2/NiS/MnS, providing a good interaction for the electrolyte. The I-J Value of 9.94% shows that the passivation with the NiS layer promotes electron transport and enhances the performance of the modified cells. The passivation of the TiO2 layer with NiS attains a better power conversion efficiency among the scant studies so far on the surface passivation of QDSCs.

Proficient One-Step Heat-Up Synthesis of Manganese Sulfide Quantum Dots for Solar Cell Applications

The necessity to develop renewable energy resources that are highly durable and flexible with superior energy density and capacitance ability has attracted considerable interest in the field of solar cell research. Semiconducting compound materials that are easily available, hazard-free and cost-effective are emerging as potential solutions to tackle this challenge. Herein, we present multiple molecular precursors used to grow manganese sulfide nanoparticles through a proficient one-step heat-up approach. For all of the tested samples, the X-ray diffraction peaks correspond to a γ-MnS hexagonal wurtzite structure. UV-Vis spectroscopy yielded absorption wavelengths of 359-420 nm and band-gap energies of 3.78-4.0 eV. Photoluminescence analysis shows characteristics of red and blue shift from 451-602 nm. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) reveal a narrow size distribution with nanosticks and large contact areas, which are critical for improved catalytic performance. The current study provides an improved pathway to a well-grown and uniform nanocrystal structure for applications in energy devices.

Enhanced light absorption and charge recombination control in quantum dot sensitized solar cells using tin doped cadmium sulfide quantum dots

The photovoltaic performance of quantum dot sensitized solar cells (QDSSCs) is limited due to charge recombination processes at the photoelectrode/electrolyte interfaces. We analyzed the effect of Sn⁴⁺ ion incorporation into CdS quantum dots (QDs) deposited onto TiO₂ substrates in terms of enhancing light absorption and retarding electron-hole recombination at the TiO₂/QDs/electrolyte interfaces. Sensitization involved depositing CdS QDs with different Sn⁴⁺ concentrations on the surface of TiO₂ using a facile and cost-effective successive ionic layer adsorption and reaction (SILAR) method. Optimized photovoltaic performance of Sn-CdS sensitized QDSSCs was explored using CuS counter electrodes (CEs) and a polysulfide electrolyte. Structural and optical studies of the photoanodes revealed that the gaps between CdS nanoparticles were partially filled by Sn⁴⁺ ions, which enhanced the light absorption of the solar cell device. Electrochemical impedance spectroscopy (EIS) and open circuit voltage decay (OCVD) tests suggested that Sn⁴⁺ ions can remarkably retard electron-hole recombination at the interfaces, stimulate electron injection into semiconductor QD layers, and provide long-term electron lifetime to the cells. We found that solar cells based on CdS photoanodes doped with 10% Sn⁴⁺ ions exhibited a superior power conversion efficiency (PCE) of 3.22%, open circuit voltage (Voc) of 0.593 V, fill factor (FF) of 0.561, and short-circuit current density (Jsc) of 9.68 mA cm^-2 under an air mass coefficient (AM) 1.5 G full sun illumination. These values were much higher than those of QDSSCs based on bare CdS photoanodes (PCE = 2.16%, Voc = 0.552 V, FF = 0.471, and Jsc = 8.31 mA cm^-2).

Carrier transport dynamics in Mn-doped CdSe quantum dot sensitized solar cells

In this work quantum dot sensitized solar cells (QDSSCs) were fabricated with CdSe and Mn-doped CdSe quantum dots (QDs) using the SILAR method. QDSSCs based on Mn-doped CdSe QDs exhibited improved incident photon-to-electron conversion efficiency. Carrier transport dynamics in the QDSSCs were studied using the intensity modulated photocurrent/photovoltage spectroscopy technique, from which transport and recombination time constants could be derived. Compared to CdSe QDSSCs, Mn-CdSe QDSSCs exhibited shorter transport time constant, longer recombination time constant, longer diffusion length, and higher charge collection efficiency. These observations suggested that Mn doping in CdSe QDs could benefit the performance of solar cells based on such nanostructures.

Shining a light on transition metal chalcogenides for sustainable photovoltaics

Transition metal chalcogenides are an important family of materials that have received significant interest in recent years as they have the potential for diverse applications ranging from use in electronics to industrial lubricants. One of their most exciting properties is the ability to generate electricity from incident light. In this perspective we will summarise and highlight the key results and challenges in this area and explain how transition metal chalcogenides are a good choice for future sustainable photovoltaics.

Improved photovoltaic performance of quantum dot-sensitized solar cells using multi-layered semiconductors with the effect of a ZnSe passivation layer

ZnSe was deposited on a TiO₂/PbS/CdS/CdSe photoanode, which was more efficient in reducing electron recombination in the QDSSCs.

Reduced recombination with an optimized barrier layer on TiO2 in PbS/CdS core shell quantum dot sensitized solar cells

A solar cell based on a double coating electrode (MgO/Al₂O₃) on TiO₂ yielded excellent performance with an efficiency (η) of 3.25%.

The effect of TiO2 nanoflowers as a compact layer for CdS quantum-dot sensitized solar cells with improved performance

Currently, TiO2 on a fluorine-doped tin oxide substrate is the most commonly used type of photoelectrode in high-efficiency quantum dot-sensitized solar cells (QDSSCs). The power conversion efficiency (PCE) of TiO2 photoelectrodes is limited because of higher charge recombination and lower QD loading on the TiO2 film. This article describes the effect of a TiO2 compact layer on a TiO2 film to enhance the performance of QDSSCs. TiO2 nanoparticles were coated on an FTO substrate by the doctor-blade method and then the TiO2 compact layer was successfully fabricated on the surface of the nanoparticles by a simple hydrothermal method. QDSSCs were made using these films as photoelectrodes with NiS counter electrodes. Under one sun illumination (AM 1.5 G, 100 mW cm(-2)), the QDSSCs showed PCEs of 2.19 and 2.93% for TCL1 and TCL2 based photoelectrodes, which are higher than the 1.33% value obtained with bare TiO2. The compact-layer-coated film electrodes provide a lower charge-transfer resistance and higher light harvesting. The compact layer on the TiO2 film is a more efficient photocatalyst than pure TiO2 film and physically separates the injected electrons in the TiO2 from the positively charged CdS QD/electrolyte.

The effect of manganese in a CdS/PbS colloidal quantum dot sensitized TiO2 solar cell to enhance its efficiency

The PbS/Mn-CdS electrode shows superior stability in a sulfide/polysulfide electrolyte with a power conversion efficiency (η) of 3.55%.