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.

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).