A New Method to Measure Trap Characteristics of Silicon Solar Cells

A new method to measure trap characteristics in crystalline silicon solar cells is presented.Important parameters of traps including energy level,total concentration of trapping centers and capture cross-section ratio of hole to electron are deduced using the Shockley-Read-Hall theory of crystalline silicon solar cells in base region.Based on the as-deduced model,these important parameters of traps are determined by measuring open-circuit voltages of silicon solar cells under monochromatic illumination in the wavelength range 500-1050 nm with and without bias light.The effects of wavelength and intensity of bias light on the measurement results are also discussed.The measurement system used in our experiments is very similar to a quantum efficiency test system which is commercially available.Therefore,our method is very convenient and valuable for detecting deep level traps in crystalline silicon solar cells.

Effect of thermal pretreatment of metal precursor on the properties of Cu_2ZnSnS_4 films

Zn/Sn/Cu （CZT） stacks were prepared by RF magnetron sputtering. The stacks were pretreated at different tem- peratures （200℃, 300 ℃, 350 ℃, and 400 ℃） for 0.5 h and then followed by sulfurization at 500℃ for 2 h. Then, the structures, morphologies, and optical properties of the as-obtained Cu2ZnSnS4 （CZTS） films were studied by x-ray diffraction （XRD）, Raman spectroscopy, UV-Vis-NIR, scanning electron microscope （SEM）, and energy-dispersive x-ray spectroscopy （EDX）. The XRD and Raman spectroscopy results indicated that the sample pretreated at 350℃ had no secondary phase and good crystallization. At the same time, SEM confirmed that it had large and dense grains. According to the UV-Vis-NIR spectrum, the sample had an absorption coefficient larger than 10^4 cm-1 in the visible light range and a band gap close to 1.5 eV.

Characterization of the nanosized porous structure of black Si solar cells fabricated via a screen printing process

A silicon（Si） surface with a nanosized porous structure was formed via simple wet chemical etching catalyzed by gold（Au） nanoparticles on p-type Cz-Si（100）.The average reflectivity from 300 to 1200 nm was less than 1.5%.Black Si solar cells were then fabricated using a conventional production process.The results reflected the output characteristics of the cells fabricated using different etching depths and emitter dopant profiles.Heavier dopants and shallower etching depths should be adopted to optimize the black Si solar cell output characteristics. The efficiency at the optimized etching time and dopant profile was 12.17%.However,surface passivation and electrode contact due to the nanosized porous surface structure are still obstacles to obtaining high conversion efficiency for the black Si solar cells.

Enhancement of ZnO ultraviolet emission by surface plasmon coupling using a rough NiSi_2 layer synthesized by ion implantation

The calculation results of the surface plasmon(SP) energy and Purcell factor of ZnO/NiSi2demonstrate the possibility of using NiSi2to enhance the UV emission of ZnO by SP coupling.Experimentally,ZnO films were deposited on NiSi2layers synthesized by ion implantation,and the roughness of the NiSi2layers spans a large range from 3 to 38 nm,providing favorable conditions for investigating SP-mediated emission.An 11-fold emission enhancement from the ZnO film on the roughest NiSi2layer was obtained,which indicates the possibility that metal silicide layers can be used both as an electrical contact and for emission enhancement.