Improved Photovoltaic Performance Of Silicon Nanoholes/ PEDOT:PSS Hybrid Heterojunction Solar Cells

With the social development and human progress, energy shortages have become increasingly serious. When conventional fossil energy can’t meet our needs gradually, scientists have to turn research to alternative renewable energy. Silicon is the most widely used material for solar cells due to its abundance, non-toxicity, reliability and mature fabrication process. At present, the high cost of the silicon solar cells is the major problem which hinders its mass application. The emerging of silicon-organic hybrid heterojunction solar cells not only combined the organic solar cells’ advantages of low cost and easy processing, but also has the excellent photoelectric properties of inorganic solar cells has drawn great interests. Such as Si/PEDOT:PSS heterojunction solar cells. It can be formed by low-cost all solution method at low temperature, through several years of development, it has achieved a record power conversion efficiency of 13.8%. In order to improve the power conversion efficiency of Si/PEDOT:PSS solar cells and cut costs, Silicon nanostructures has been used in hybrid solar cells. Silicon nanostructures including silicon nanowires, pyramids and nanoholes with excellent light absorption properties which can greatly reduce the consumption of silicon materials. The nanostructures also exhibit the advantages to offer larger junction area and more effective separation pathways for charge carriers. So, based on above, in this letter, we investigated how to improve the light absorption and power conversion efficiency of silicon nanoholes/PEDOT:PSS hybrid solar cells. The major work can be summarized as below:1. Silver nanoparticles were synthesized by sodium reduction method, Silicon nanoholes /PEDOT:PSS nanocomposite films were fabricated by Ag nanoparticles assisted electroless etching (EE) method. SEM was used to observe the morphology of samples, the silicon nanoholes were formed in good condition and Ag nanoparticles were embedded in the nanoholes. After exploring the silicon nanoholes in the air to make the surface form SiOx-Si bonds, PEDOT:PSS was spin-coated on the film to fabricated solar cells. As the result, the performance of solar cells based on silicon nanoholes was better than plane silicon, the short-circuit current density exhibited an enhancement of 75%, the power conversion efficiency was increased from 1.1% to 2.4%. After passivating the surface of silicon nanoholes, the highest PCE reaches a record of 5.5% in comparison to 4.8% from the reference counterpart, the short-circuit current density was enhanced from 23.6mA/cm2 to 26.1 mA/cm2.2. Gold nanoparticles were synthesized by sodium reduction method, TEM image shows the average diameter of Au nanoparticles was 50nm. We used Shimadzu UV-3600 spectrophotometer to measure and calculate the absorbance spectrum of Au and Ag nanoparticles. We found that the absorption peak of Au and Ag nanoparticles is near 530nm and 460nm. PEDOT:PSS blended with Au nanoparticles were spin-coated on the surface of Si nanoholes to fabricated nanocomposite films. Through the light absorption spectrum of samples, the best mass ratio of Au nanoparticles is 0.5wt%. The localized surface plasmon resonance (LSPR) effect caused by Au and Ag nanoparticles can extend the absorption peak of samples. The EQE values of the solar cells with Au nanoparticles are higher than that of the samples without Au nanoparticles in the spectral region of 600nm-1000nm. The PCE of the solar cells incorporating Au nanoparticles increased from 5.5% to 6.1%, exhibited an enhancement of 27%, compared with that of the solar cells without Au nanoparticles. So, introduced metal nanoparticles with different localized surface plasmon resonance absorption peak into solar cells is better to power conversion efficiency.We think, the improved efficiency was attributed to localized surface plasmon resonance triggered by metal nanoparticles and surface modification of Si nanoholes.