Performance Optimization Of Novel Solar Cells By Au-nanoparticles And Scattering Of Microspheres

To find and utilize clean and renewable energy is one of the major tasks that human beings need to complete in the 21st century.Solar energy is a competitive clean renewable energy source.New types of solar cells represented by dye-sensitized solar cells(DSSCs)and perovskite solar cells(PSCs)bring new hope and opportunity to alleviate the energy problem faced by human beings.In this paper,functional nano-materials are incorporated into the photoanodes of DSSCs via doping modification and structural optimization to enhance the performance of DSSCs.Based on the study of DSSCs,PSCs are preliminarily explored.The main contents are summarized as follows:1)Composite photoanode films with hierarchical TiO2 microspheres(TMSs)are prepared and incorporated into photoanodes to form novel DSSCs.The influence of different TMS concentrations and gradient structures on the performance of photoanodes and DSSCs are studied.The results indicated that the optimal properties were obtained in the cell with the introduction of 33wt%TMSs.The maximum short circuit current density(Jsc)and photoelectric conversion efficiency(PCE)of this cell are 14.90 mA cm-2 and 6.57%,respectively.Maintaining the overall concentration of TMSs as the optimal one,different kinds of multi-layer photoanodes with different gradient structures were designed.The results indicated that the optimal gradient-ascent architecture of DSSC exhibits the maximum Jsc of 16.49 mA cm-2 and PCE of 7.01%,higher than those of the uniform multi-layer DSSC by 10.7%and 6.7%,and notably higher than those of the conventional DSSC without TMSs by 21.8%and 21.1%,respectively.The main reasons for the significant performance improvements of DSSCs are that the optimal-concentra-tion-gradient-ascent and multi-layer-arrangement structure of the microspheres in photoanodes increases dye absorption,and microsphere scattering can maximally localize incident light within the photoanode films,thus significantly increasing the utilization of the incident light and the Jsc and PCE of DSSCs.2)The Au nanoparticle sandwiched double spheric-shells of SiO2@Au@TiO2(SAT)microspheres are synthesized.The SAT microspheres are incorporated with different concentrations into the photoanode films to form the composite structure of photoanodes.Studies indicate that the composite structure with SAT microspheres can markedly enhance the scattering and harvesting ability of incident light,and increase the lifetime of carrier.The maximum Jsc,of 17.0 mA·cm-2 and PCE of 7.14%are obtained in the DSSC with optimal SAT microspheres doping rate of 2.25wt%.Compared with the conventional DSSC with TiO2 photoanodes,the Jsc and PCE are improved by 15.7%and 21.2%,respectively.These significant enhancements in the performance of DSSCs are attributed to the localized surface plasmon resonance(LSPR)effect of the AuNPs that can improve light absorption and stimulate photogenerated carriers,and the excellent light scattering and reflection of the SAT microspheres to increase the harvesting rate of incident light.This demonstrates the synergetic complementary effect between the light scattering of the double spheric-shell microspheres and the LSPR effect of Au NPs.3)Based on the research of TMS optional concentrations and structure optimization,the above SAT microspheres are introduced into the photoanodes of DSSC with various gradient structure.The results indicate that the concentration-gradient-ascent distribution of the SAT microspheres can significantly enhance the light scattering and harvesting capability of photoanodes.The DSSCs using the photoanodes with the optimal SAT gradient-ascent structure achieve the maximum Jsc of 17.7 mA cm-2 and PCE of 7.75%,remarkably higher than those of conventional DSSCs by 23.7%and 28.0%.The main reasons include:the good light scattering and reflection effect of the SAT microspheres can effectively increase the optical path of incident light to improve the light harvesting ability;the LSPR effect of the Au NPs can increase light absorption and produce more photo-generated carriers;The concentration-gradient-ascent distribution of the SAT microspheres can make incident light be continuously enhanced and fully scattered and maximally localized within the photoanode films to be absorbed by dye as much as possible and converted into photo-generated electronics.4)Based on the research approach of DSSCs,Au nanorod core-shell structure(AuNRs@SiO2)is introduced into mesoporous layer of PSCs to improve the optical absorption property of PSCs.The effect of different AuNRs@SiO2 concentrations on the performance of carbon-based free-hole transport lay,er of PSCs is studied.The results show that the Jsc,open circuit voltage(Voc)and PCE of the PSCs increase firstly and then decrease with the increase of the amount of AuNRs@SiO2.The PCE,Jsc and Voc of the PSC with 3.0%AuNRs@SiO2 reach the maximum values of 13.02%,21.05 mA cm-2 and 970 mV,respectively,higher than those of the traditional PSCs without AuNRs@SiO2 incorporation by 26%,14.4%and 3%,respectively.