Hybrid Organic-inorganic Solar Cell Based On Silicon Nanowire Array And Conjugated Molecules

In recent years, due to the petroleum extinction and environmental pollutionproblem, photovoltaics (PV) have become a most pursued renewable energy technology.At present, crystallized silicon photovoltaics have hold more than80%market sharebecause of their non-toxic, abundant raw materials and the long-term stability.However，the cost of cell is still too high limiting its widespread use. In order to reducethe cell cost, oranic-inorganic hybrid solar cell based on silicon nanowire arrayarchitecture (SiNWs) and conjugated moleculas are investigated.In the traditional high efficient planar silicon cells, in order to ensure collection ofthe photogenerated charge carriers, minority-carrier diffusion length needs to becompatible with the ultra long absorption optical depth (up to200μm), which isassociated with the indirect band gap semiconductor properties, therefore highlypurified crystalline as well as thick absorption sheet is required. Comparing with theplanar silicon cells, hybrid radial heterojunction solar cells based on SiNWs andconjugated moleculas have several advantages. First, the radical junction based onSiNWs which shows excellent light harvesting capability and efficient charge-carrierextraction can reduce the amount as well as the purify of silicon used in the cell. Second,the hybrid heterojunctions take advantage of the solution-based processes of conjugatedmoleculas, which simplify the fabrication processes and reduce the manufacturing costof the cell.The main subject of this work is to fabricate the low-cost and high-efficiency PVcells composed of SiNWs and conjugated moleculas. Here, the SiNWs are fabricated bythe metal-assisted solution etching method and passivated by methylation. The majorwork can be summarized as follows:1、Photoelectrochemical (PEC) cells based on different Si electrodes and ionicliquid (IL) are fabricated. The X-ray photoelectron spectrum measurement and thestability measurement of the cell shows that methylation and IL can protect the silicon from oxidation. The moderate efficiency and the excellent stability of the PEC celldemonstrate that the cell may have the potential of practical use.2、Heterojunction solar cells based on SiNWs and Spiro-OMeTAD are fabricatedby a simple solution method. The devices with radial junction show excellent efficiencyof~10.0%. By comparing the performance of the device with core-shell structure to thatof the device with the embedded one as well as the planar one, the necessity of radialjunction with core-shell structure is outlined.3、In addition to the AFM and SKPM images of PEDOT:PSS films, by analyzingthe current density-voltage curves, the capantance-voltage measurements and thetransient photovoltage measurements of the Schottky cells composed of Silicon andPEDOT:PSS, the poor reproducibility of Si/PEDOT:PSS cell as well as the the influenceof PEDOT:PSS film is investragated.4、The method which shows good repeatability of the Silicon/PEDOT:PSS cells isdemonstrated. Simply simulate the work function of PEDOT:PSS affection to theSilicon/PEDOT:PSS cell. The efficiency can be increased14%when the particles of Ptand TiC are added to the PEDOT:PSS films, attaining the value of10.35%.