Xiaoping Zou

Performance study of CdS/Co-Doped-CdSe quantum dot sensitized solar cells

In order to optimize the charge transfer path in quantum dot sensitized solar cells (QDSCs), we employed successive ionic layer adsorption and reaction method to dope CdSe with Co for fabricating CdS/Co-doped-CdSe QDSCs constructed with CdS/Co-doped-CdSe deposited on mesoscopic TiO2 film as photoanode, Pt counter electrode, and sulfide/polysulfide electrolyte. After Co doping, the bandgap of CdSe quantum dot decreases, and the conduction band and valence band all improve, forming a cascade energy level which is more conducive to charge transport inside the solar cell and reducing the recombination of electron-hole thus improving the photocurrent and ultimately improving the power conversion efficiency. This work has not been found in the literature.

Cu-Doped-CdS/In-Doped-CdS Cosensitized Quantum Dot Solar Cells

Cu-doped-CdS and In-doped-CdS cosensitized (Cu-doped-CdS/In-doped-CdS) quantum dot solar cells (QDSCs) are introduced here. Different cosensitized sequences, doping ratios, and the thickness (SILAR cycles) of Cu-doped-CdS and In-doped-CdS are discussed. Compared with undoped CdS QDSCs, the short circuit current density, UV-Vis absorption spectra, IPCE (monochromatic incident photon-to-electron conversion), open circuit voltage, and so on are all improved. The photoelectric conversion efficiency has obviously improved from 0.71% to 1.28%.

CdTeO 3 deposited mesoporous NiO photocathode for a solar cell

Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR) method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE) value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

Enhancement of electron transfer efficiency in solar cells based on PbS QD/N719 dye cosensitizers

Cosensitized solar cells (CSSCs) have recently become an active subject in the field of sensitized solar cells (SSCs) due to their increasing electronic utilization. However, because of the dye molecules, layer must be single, dye-SSCs cannot be co-sensitized with two different dyes to form two different molecules layer. But it is possible to be cosensitized with quantum dots (QDs) and dyes. Here we designed novel photoanode architecture, namely, PbS QDs and N719 dyes are used as co-sensitizers of the TiO2 mesoporous film. The experimental result shows that PbS QDs/N719 dyes co-sensitized structure can make PbS QDs and N719 dyes mutual improvement. Taking the advantage of PbS not only achieved higher transfer efficiency of photo-excited electron, but also achieved obviously wider range and higher intensity of absorption. The PbS QDs which have been deposited on the TiO2 film was coated by N719 dyes, which can effectively prevent PbS QDs from corroding by I-/I3-3 electrolyte and light. As we expected, the solar energy-conversion efficiency which is showed by CSSCs fabricated following these photoanodes is relatively higher than the PbS QDs or N719 dyes, single-sensitized solar cells under the illumination of one sun.

Heterovalent Cation Substitutional and Interstitial Doping in Semiconductor Sensitizers for Quantum Dot Cosensitized Solar Cell

Doped films of TiO2/PbS/CdS have been prepared by successive ionic layer adsorption and reaction (SILAR) method. Bi- and Ag-doped-PbS quantum dot (QD) were produced by admixing Bi3

Doped Heterojunction Used in Quantum Dot Sensitized Solar Cell

Incorporated foreign atoms into the quantum dots (QDs) used in heterojunction have always been a challenge for solar energy conversion. A foreign atom indium atom was incorporated into PbS/CdS QDs to prepare In-PbS/In-CdS heterojunction by successive ionic layer adsorption and reaction method which is a chemical method. Experimental results indicate that PbS or CdS has been doped with In by SILAR method; the concentration of PbS and CdS which was doped In atoms has no significantly increase or decrease. In addition, incorporating of Indium atoms has resulted in the lattice distortions or changes of PbS or CdS and improved the light harvest of heterojunction. Using this heterojunction, Pt counter electrode and polysulfide electrolyte, to fabricate quantum dot sensitized solar cells, the short circuit current density ballooned to 27.01 mA/cm2 from 13.61 mA/cm2 and the open circuit voltage was improved to 0.43 V from 0.37 V at the same time.

Effect of Annealing Process on CH3NH3PbI3-XClX Film Morphology of Planar Heterojunction Perovskite Solar Cells with Optimal Compact TiO2 Layer

The morphology of compact TiO2 film used as an electron-selective layer and perovskite film used as a light absorption layer in planar perovskite solar cells has a significant influence on the photovoltaic performance of the devices. In this paper, the spin coating speed of the compact TiO2 is investigated in order to get a high-quality film and the compact TiO2 film exhibits pinhole- and crack-free films treated by 2000 rpm for 60 s. Furthermore, the effect of annealing process, including annealing temperature and annealing program, on CH3NH3PbI3-XClX film morphology is studied. At the optimal annealing temperature of 100°C, the CH3NH3PbI3-XClX morphology fabricated by multistep slow annealing method has smaller grain boundaries and holes than that prepared by one-step direct annealing method, which results in the reduction of grain boundary recombination and the increase of Voc. With all optimal procedures, a planar fluorine-doped tin oxide (FTO) substrate/compact TiO2/CH3NH3PbI3-XClX/Spiro-MeOTAD/Au cell is prepared for an active area of 0.1 cm2. It has achieved a power conversion efficiency (PCE) of 14.64%, which is 80.3% higher than the reference cell (8.12% PCE) without optimal perovskite layer. We anticipate that the annealing process with optimal compact TiO2 layer would possibly become a promising method for future industrialization of planar perovskite solar cells.

Effect of Perovskite Film Preparation on Performance of Solar Cells

For the perovskite solar cells (PSCs), the performance of the PSCs has become the focus of the research by improving the crystallization and morphology of the perovskite absorption layer. In this thesis, based on the structure of mesoporous perovskite solar cells (MPSCs), we designed the experiments to improve the photovoltaic performance of the PSCs by improved processing technique, which mainly includes the following two aspects. Before spin-coating PbI2 solution, we control the substrate temperature to modify the crystal quality and morphology of perovskite films. On the other hand, before annealing, we keep PbI2 films for the different drying time at room temperature to optimize films morphology. In our trials, it was found that the substrate temperature is more important in determining the photovoltaic performance than drying time. These results indicate that the crystallization and morphology of perovskite films affect the absorption intensity and obviously influence the short circuit current density of MPSCs. Utilizing films prepared by mentioning two methods, MPSCs with maximum power conversion efficiency of over 4% were fabricated for the active area of 0.5 × 0.5 cm2.

Effect of Modulating Spin-Coating Rate of TiO2 Precursor for Mesoporous Layer on Hysteresis of Solar Cells with Polar CH3NH3PbI3 Perovskite Thin Film

Compared with the crystalline Si solar cells, the - characteristics of CH3NH3PbI3 perovskite solar cells are different under forward and reverse scan, and the CH3NH3PbI3 film exhibits some polarization properties. To explore those performances of the mesoporous TiO2 layer based perovskite solar cells, we focus on the effect of modulating the spin-coating rate of the TiO2 precursor for mesoporous layer on - hysteresis of solar cells with the polar film by - curves, atomic force microscopy topographic images, and piezoresponse force microscopy phase images. Firstly, the AFM images illustrate that the polarization behaviors exist and the deformation scale is large at the corresponding position when the DC bias voltage increases. Secondly, it is suggested that the polar films which applied the positive DC biases voltage show a tendency to 0° phase angle, while the polar films which applied the negative DC biases voltage show a tendency to −180° phase angle. Thirdly, a weak polar hysteresis loop relation for CH3NH3PbI3 film was observed. Finally, the hysteresis index for the 1500 rpm mesostructured solar cell shows relatively low - hysteresis compared with the 3000 rpm mesostructured and the planar-structured solar cell. Our experimental results bring novel routes for reducing the hysteresis and investigating the polar nature for CH3NH3PbI3 material.

Effect of Codoping Cl Anion and 5-AVA Cation on Performance of Large-Area Perovskite Solar Cells with Double-Mesoporous Layers

For the perovskite solar cells (PSCs), the performance of the PSCs has become the focus of the research by improving the quality of the perovskite absorption layer. So far, the performance of the large-area PSCs is lower than that of small-area PSCs. In the paper, the experiments were designed to improve the photovoltaic performance of the large-area PSCs by improved processing technique. Here we investigated the optoelectronic properties of the prototypical CH3NH3PbI3 (MAPbI3) further modulated by introducing other extrinsic ions (specifically codoped Cl− and 5-AVA