Efficient quantum dot sensitized solar cells via improved loading amount management

High light-harvesting efficiency and low interfacial charge transfer loss are essential for the fabrication of high-efficiency quantum dot-based solar cells(QDSCs). Increasing the thickness of mesoporous TiO2films can improve the loading of pre-synthesized QDs on the film and enhance the absorbance of photoanode, but commonly accompanied by the increase in the unfavorable charge recombination due to prolonged electron transmission paths. Herein, we systematically studied the influence of the balance between QD loading and TiO2film thickness on the performance of QDSCs. It is found that the relative thin photoanode prepared by the cationic surfactant-assisted multiple deposition procedure has achieved a high QD loading which is comparable to that of the thick photoanode commonly used. Under AM 1.5G illumination, Zn–Cu–In–Se and Zn–Cu–In–S based QDSCs with optimized 11.8 μm photoanodes show the PCE of 10.03% and 8.53%, respectively, which are comparable to the corresponding highest PCE of Zn–Cu–In–Se and Zn–Cu–In–S QDSCs(9.74% and 8.75%) with over 25.0 μm photoanodes. Similarly, an impressive PCE of 6.14% was obtained for the CdSe based QDSCs with a 4.1 μm photoanode, which is slightly lower than the best PCE(7.05%)of reference CdSe QDSCs with 18.1 μm photoanode.

CdS Quantum Dots-sensitized TiO_2 Nanotube Arrays for Solar Cells

CdS quantum dots（QDs） sensitized TiO2 nanotube arrays photoelectrodes were investigated for their photovoltaic performance of quantum dots-sensitized solar cells. The highly ordered TiO2 nanotube arrays（TNAs） were synthesized on Ti foils by anodic oxidation method. Then CdS quantum dots were deposited onto the TiO2 nanotube arrays by successive ionic layer absorption and reaction（SILAR） method to serve as the sensitizers. Cd（NO3）2 and Na2S were used as the precursor materials of Cd＋ and S2- ions, respectively. It is found that the CdS QDs sensitizer may significantly increase the light response of TiO2 nanotube arrays. With increasing CdS QDs deposition cycles, the visible light response increases. Maximum photocurrent was obtained for the QDs that have an absorption peak at about 500 nm. Under AM 1.5 G illuminations（100 mW cm^-2）, a 4.85 mA/cm^2 short circuit current density was achieved, and the maximium energy conversion efficiency of the asprepared CdS QDs-sensitized TNAs solar cells was obtained as high as 0.81% at five SILAR cycles.

Decrease of back recombination rate in CdS quantum dots sensitized solar cells using reduced graphene oxide

The photovoltaic performance of CdS quantum dots sensitized solar cells （QDSSCs） using the 0.2 wt% of reduced graphene oxide and TiO2 nanoparticles （RGO＋TiO2 nanocomposite） photoanode is investigated. CdS QDs are adsorbed onto RGO＋TiO2 nanocomposite films by the successive ionic layer adsorption and reaction （SILAR） technique for several cycles. The current density-voltage （J-V） characteristic curves of the assembled QDSSCs are measured at AM1.5 simulated sunlight. The optimal photovoltaic performance for CdS QDSSC was achieved for six SILAR cycles. Solar cells based on the RGO＋TiO2 nanocomposite photoanode achieve a 33% increase in conversion efficiency （η） compared with those based on plain TiO2 nanoparticle （NP） photoanodes. The electron back recombination rates decrease significantly for CdS QDSSCs based on RGO＋TiO2 nanocomposite photoanodes. The lifetime constant （τ） for CdS QDSSC based on the RGO＋TiO2 nanocomposite photoanode is at least one order of magnitude larger than that based on the bare TiO2NPs photoanode.

Design and mechanism insight on SiC quantum dots sensitized inverse opal TiO_(2) with superior photocatalytic activities under sunlight

The combination of SiC quantum dots sensitized inverse opal TiO_(2) photocatalyst is designed in this work and then applied in wastewater purification under simulated sunlight.From various spectroscopic techniques,it is found that electrons transfer directionally from SiC quantum dots to inverse opal TiO_(2),and the energy difference between their conduction/valence bands can reduce the recombination rate of photogenerated carriers and provide a pathway with low interfacial resistance for charge transfer inside the composite.As a result,a typical type-II mechanism is proved to dominate the photoinduced charge transfer process.Meanwhile,the composite achieves excellent photocatalytic performances(the highest apparent kinetic constant of 0.037 min^(-1)),which is 6.2 times(0.006 min^(-1))and 2.1 times(0.018 min^(-1))of the bare inverse opal TiO_(2) and commercial P25 photocatalysts.Therefore,the stability and non-toxicity of SiC quantum dots sensitized inverse opal TiO_(2) composite enables it with great potential in practical photocatalytic applications.

Boosting the efficiency of quantum dot–sensitized solar cells over 15%through light-harvesting enhancement

How to improve the capacity of light-harvesting is still an important point and essential strategy for the assembling of high-efficiency quantum dot–sensitized solar cells(QDSCs).A believable approach is to implant new light absorption materials into QDSCs to stimulate the charge transfer.Herein,the few-layer black phosphorus quantum dots(BPQDs)are synthesized by electrochemical intercalation technology using bulk BP as source.Then the obtained BPQDs are deposited onto the surface of Zn–Cu–In–S–Se(ZCISSe)QD-sensitized TiO2 substrate to serve as another light-harvesting material for the first time.The experimental results have shown that BPQDs can not only increase the absorption intensity by photoanode but also reduce unnecessary charge recombination processes at the interface of photoanode/electrolyte.Through optimizing the size and deposition process of BPQDs,the champion power conversion efficiency of ZCISSe QDSCs is increased to 15.66%(26.88 mA/cm2,Voc=0.816 V,fill factor[FF]=0.714)when compared with the original value of 14.11%(Jsc=25.41 mA/cm^(2),Voc=0.779 V,FF=0.713).

Optical properties and dynamic process in metal ions doped on CdSe quantum dots sensitized solar cells

In recent years, the nanostructure for solar cells have attracted considerable attention from scientists as a result of a promising candidate for low cost devices. In this work, quantum dots sensitized solar cells with effective performance based on a co-sensitized Cd S∕Cd Se：Mn2＋（or Cu2＋） nanocrystal, which was made by successive ionic layer absorption and reaction, are discussed. The optical, physical, chemical, and photovoltaic properties of quantum dots sensitized solar cells were sensitized to Mn2＋and Cu2＋dopants. Therefore, the short current（JSC）of the quantum dot sensitized solar cells is boosted dramatically from 12.351 mA∕cm2 for pure Cd Se nanoparticles to 18.990 mA∕cm2 for Mn2＋ions and 19.915 mA∕cm2 for Cu2＋ions. Actually, metal dopant extended the band gap of pure Cd Se nanoparticles, reduced recombination, enhanced the efficiency of devices, and improved the charge transfer and collection. In addition, Mn2＋and Cu2＋dopants rose to the level of the conduction band of pure Cd Se nanoparticles, which leads to the reduction of the charge recombination, enhances the lightharvesting efficiency, and improves the charge diffusion and collection. The results also were confirmed by the obtained experimental data of photoluminescence decay and electrochemical impedance spectroscopy.