Enhancement Of Photovoltaic Performance Of SiNW/PEDOT:PSS Hybrid Solar Cells

In order to meet the growing energy demand and response to the problem of climate change and environmental pollution,solar power,as an inexhaustible?clean and green energy,has received considerable attention and intensive research.Solar cells,as an important means of solar energy utilization,achieved great development in the past decades.The silicon/PEDOT:PSS hybrid solar cell provides the possibility of making a kind of solar cells with low cost and high efficiency,because this kind of solar cell has not only the organic solar cell's advantages of low cost and easy processing,but also the excellent photoelectric properties of inorganic semiconductors.However,the lower efficiency of the hybrid solar cells at the present stage is the major problem which hinders its mass production.The main subject of this thesis is to research the modified performance of hybrid solar cell from the following two aspects:First,via introducing the materials which can increase the absorption of solar light in the SiNW/PEDOT:PSS hybrid solar cells,we enhanced the optical absorption and improved the photoelectric performance of the device.Second,via regulating the length and morphology of silicon nanowires,we optimized the performance of the SiNW/PEDOT:PSS hybrid solar cells.Based on the above,we etched the silicon nanowires by the metal assisted etching method,and fabricated a series of hybrid solar cell.The major work can be summarized as below:1?We synthesized the uniformly sized Cadmiun Telluride quantum dots(CdTe QDs)by aqueous phase method.The UV3600 spectrophotmeter and photoluminescence instrument were used to observe the obsorption and the photoluminescence(PL)spectrum of CdTe QDs.The result showed that the CdTe QDs absorbed the shorter wavelength sunlight(300?500 nn)and emited the longer wavelength light(500?600 nm).Compared to the EQE of the silicon nanowire hybrid solar cells,the PL spectra of the CdTe QDs ovelap with the maximum spectral response region of the SiNW hybrid solar cell.It is possible that the down-shifting effect in the near-UV region of CdTe QDs will increase the optical absorption of hybrid solar cells.We introduced an intermediate Cadmium telluride quantum dots(CdTe QDs)layer between the organic with silicon nanowires of hybrid solar cells and fabricated SiNW/CdTeQD/PEDOT:PSS hybrid solar cells.We fabricated three devices with different density of CdTe QDs layer,the different density of CdTe QDs were gained by controlling the cycles of the spin-coating.The optimal value for spin-coating cycles is 6,at which solar cell displays the following performance:short circuit current density(Jsc),open circuit voltage(Voc),fill factor(FF)and power conversion efficiency(PCE)are 26.8mA/cm2,511mV,44%and 6.1%,respectively.Finaly,we also fabricated the SiNW/CdTeQD/PEDOT:PSS hybrid solar cells via spin-coating CdTe QDs on the surface of PEDOTP:SS polymer and the SiNW/PEDOT:PSS:CdTeQD hybrid solar cells using spin-coating the mixture of CdTe QDs and PEDOTP:SS polymer on the surface of SiNWs.The result showed that the SiNW/CdTeQD/PEDOT:PSS hybrid solar cells had the optimal photovoltaic performance.2?Gold nanospheres and nanorods were synthesized by sodium citrate reduction method and seed growth method,respectively.Transmission electron microscope(TEM)were used to observe the morphology of gold nanoparticles.The diameter of gold nanospheres is about 15nm,the size of gold nanorods is 20nm in diameter and 50nm in length.The performance of the SINW/PEDOT:PSS hybrid solar cell introduced in gold nanoparticles was measured.Though the surface plasmon resonance of gold nanoparticles wasn't observed in the hybrid solar cells,the Voc and FF of the hybrid solar cells were enhanced when gold nanoparticles were spin-coated between the SiNW and PEDOT:PSS polymer.The PCE of the hybrid solar cell with gold nanospheres and gold nanorods increased from 6.7%to 8.0%and 8.4%,respectively.The Jsc increased to 31.2 mA/cm2 when PEDOT:PSS polymer were mixed with gold nanorods.3?The silicon were etched different time with an etchant consisting of 5M/L HF acid and 0.02M/L AgNO3 in room temperature,and silicon nanowires with different length were fabricated.We measured the performance of hybrid solar cells with different silicon nanowire length and gained the optimal length of silicon nanowires.The optimal length of silicon nanowires is 0.23?m,at which SiNW/PEDOT:PSS hybrid solar cell displays the following performance:Jsc,Voc,FF and PCE are 30.1mA/cm2,569mV,55%and 9.3%,respectively.The optical absorption of silicon nanowires with different lengths was simulated using the finite difference time domain(FDTD)method.The result of simulation concided well with that of experiment.Finally,we studied the impact on the morphology of silicon nanowires with etchant solutions of different concentration.The TEM images showed that the silicon nanowire etched with diluted solution were disconnected with each other,the silicon nanowire etched with high concentration solution were uniform and connected.We also measured the photovoltaic performance of SiNW/PEDOT:PSS hybrid solar cells which were fabricated with the silicon nanowires etched by solution of different concentrations.The result showed that the performance of solar cells were improved when the silicon nanowires were more independent and sparse.The Jsc has a significant enhancement,from 30.1mA/cm2 to 33.2mA/cm2,increased by 10.6%.The Voc and FF of the hybrid solar cells with different morphology of silicon nanowires have no significant change.As a result,the PCE of the cell increases from 9.3%to 9.8%.