Three dimensional crystalline silicon solar cells

Download
2018
Baytemir, Gülsen
Three-dimensional crystalline silicon solar cells have been attracting attention with its remarkable electrical and optical performance. In this geometry, nano/micropillars allow minority carrier collection in the radial direction and shorten the path length of the photogenerated carriers. Furthermore, with appropriate geometry of the pillars the solar cell efficiency is enhanced due to the reduced surface reflectance and increased light harvesting. Throughout this study, metal assisted etching (MAE), a top-down method was applied through photolithography to fabricate micropillars. Firstly, radial junction cells with different micropillar lengths, including the longest ~6 µm, were fabricated by applying different etching durations. The maximum efficiency value, 15.90 %, was obtained from the cell with longest micropillars since with the increase in pillar length, higher Jsc values were obtained due to the reduced surface reflection and higher junction area. Radial and planar junction solar cells were then fabricated using Si wafers contaminated with Au impurities having U-shape diffusion profile in Si. The efficiencies of the radial junction solar cells, which allow photogenerated carriers to be collected over shorter distances, were less affected by contamination than planar junction solar cells. This is consistent with the expectation that the cells with radial geometry are less sensitive to the quality of the material used. Moreover, the solar cells with different thicknesses were fabricated to increase the proportion of the region containing micropillars in the cell and to reduce the fabrication cost by allowing the use of thin Si substrates. Firstly, longer micropillars were obtained by increasing HF concentration in the MAE solution to suppress the lateral etching and instead of H2O, using ethanol which has a lower surface tension to obtain smooter etching. The efficiency value of 17.27 %, one of the highest efficiency values in radial junction cells, was obtained from the cell containing 11.5 µm micropillars. By decreasing the thickness of the cells, it was observed that the efficiency values were less affected in three dimensional solar cells than in planar junction cells due to less decrease in Voc and Jsc values.

Suggestions

Surface modification of multi-crystalline silicon in photovoltaic cell by laser texturing
Radfar, Behrad; Turan, Raşit; Yerci, Selçuk; Department of Micro and Nanotechnology (2019)
Surface of crystalline silicon solar cell plays an important role in its performance. It affects the optical properties which can be determined by surface’ reflectance. To minimize the reflection from the flat surface, thus, improve light trapping, the crystalline silicon wafers must be textured. Through the texturing process, roughness is introduced at the surface, so the incident light has a larger probability of being absorbed into the solar cell. Monocrystalline silicon solar cells can typically be text...
Fabrication and characterization of PEDOT:PSS hole transport layers for silicon solar cells
Türkay, Deniz; Yerci, Selçuk; Department of Micro and Nanotechnology (2019)
Heterojunction silicon solar cells have gained considerable interest in recent years with the demonstration of record-high device performances. However, these devices are typically based on inorganic layers fabricated at high temperatures under vacuum environment, using toxic precursors. The low temperature budget, non-toxic chemical contents, and wide range of adjustability in physical and electrical properties make poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) a promising candidate a...
Fabrication of thin crystalline silicon solar cells with advanced light trapping
Hadibrata, Wisnu; Yerci, Selçuk; Turan, Raşit; Department of Micro and Nanotechnology (2017)
Thin crystalline silicon (c-Si) solar cells with thickness in the order of few tens of microns offer many attractive applications, such as, electronic wearables, space probes and satellites thanks to their flexibility and light-weight character. However, reducing the thickness of active layer of silicon solar cells leads to poor light absorption within the silicon layer, especially in the near infrared region of the solar spectrum. The poor absorption becomes problematic for thin c-Si solar cells as it caus...
Contact resistivity analysis of different passivation layers via transmission line method measurements
Kökbudak, Gamze; Turan, Raşit; Yerci, Selçuk; Department of Micro and Nanotechnology (2017)
Crystalline silicon (c-Si) homojunction solar cells constitute over 90% of the current photovoltaic market. Although the standard solar cells are cost effective and easy to process, their efficiency potential is unfortunately limited. Currently, more innovative cell concepts appeared with their high efficiency potential coupled with low costs. Since the recombination at surfaces and under metal contacts is one of the major obstacles against high conversion efficiencies, surface passivation has primary impor...
Imaging solar cells using terahertz waves
Kayra, Seda; Altan, Hakan; Department of Physics (2011)
In this thesis, Terahertz Time-Domain spectroscopy (THz-TDS) was used in order to measure the electrical properties of silicon solar cells. The advantage of THz-TDS is that it allows us to measure the electrical properties without electrical contacts. In order to perform these measurements, a reflection based system was constructed and the changes in the peak amplitude in the time-domain under a, 450mW 808 nm continuous wave laser source were measured. The solar cell that was used in this thesis was manufac...
Citation Formats
G. Baytemir, “Three dimensional crystalline silicon solar cells,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.