Transition-metal Semiconductor Compounds Used For High-performance New-Generation Solar Cells

Here, two transition metal compounds in solar cells based on organic and inorganic materials have been investigated. This thesis comprises of two parts: 1. High performance organic-inorganic hybrid solar cells based on silicon substrate and conductive conjugated polymer poly(3,4-ethylenedioxythiophene)/ poly(styrenesulfonate) PEDOT:PSS film; 2. Solution-processed organic photovoltaic devices based on poly(3-hexyl-thiophene)(P3HT): fullerence derivative(PC61BM) and thieno[3,4-b]thiophene/benzodithiophene(PTB7): fullerence derivative(PC71BM). The main works include the following aspects.1. Organic-inorganic hybrid solar cells have been fabricated by using planar silicon substrate and solution-processed PEDOT:PSS layer. Sheet-like cobalt sulfide, which can be synthesized by a typical hydrothermal reaction, is added in the PEDOT:PSS layer. The sheet-like cobalt sulfide has an excellent dispersity in PEDOT:PSS layer. At the same time, it can improve the conductivity and work function of this layer, leading to an increase of power conversion efficiency(PCE) from 9.46% to 11.22%.2. High-density silicon nanowire arrays(Si NWs) can be easily prepared by metal ion-assisted aqueous etching method. The Si NWs are further modified by TMAH to decrease the trap-states and density. The organic-inorganic hybrid solar cells have been fabricated using silicon substrate with double-sided silicon nanowire arrays. Furthermore, Zn O nanoparticles are spin-casted on the rear side of silicon substrate as hole blocking layer. The PCE of this kind of device has been further improved to 12.52%. The increase is attributed to the improvement of light absorption caused by Si NWs as well as the decrease of recombination on the rear side caused by Zn O layer.3. Organic photovoltaic(OPV) devices based on P3HT:PCBM and PTB7:PCBM are investigated. By doping sheet-like Co S into active layers, the microstructures of active layers are improved, and the crystallizations of organic materials are enhanced as well, which can be clearly observed by using systematic synchrotron-based Grazing Incidence X-ray Diffraction(GIXRD) experiments. The P3 HT with more edge-on and face-on structure or PTB7 with better face-on structure can provide more charge transfer channels. Therefore, the mobility of active layer can be improved. Through this method, the efficiencies of organic photovoltaic devices can be increased to 4.46%(P3HT:PCBM) and 9.28%(PTB7:PCBM), respectively.