Silicon/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid solar cells are attractive as they leverage on the excellent electrical transport properties of Si and low temperature and low cost solution based processing advantage of organic conjugated polymer [1]. To reduce parasitic absorption in PEDOT:PSS, back-junction cell has been proposed where PEDOT:PSS is placed at the back of the cell [2, 3]. In this work, we simulate back-junction cell incorporated with interdigitated back-contact, as shown in Fig. 1, to further improve the device performance by lowering sensitivity to surface recombination and eliminating grid shadowing.The cells are investigated using 2D numerical simulation based on Silvaco ATLAS.

The effects of Si doping, minority carrier lifetime, Si-cathode surface recombination, emitter contact width, and Si-PEDOT:PSS interface defect on the device performance have been investigated. Si doping concentration of 10¹⁶/cm³ is recommended for high open circuit voltage, low series resistance and robust performance at various wafer lifetimes. The use of the interdigitated back-contact is found to substantially lower the sensitivity of the cell performance to surface recombination, resulting in a more robust cell. An optimized emitter contact width exists to facilitate effective minority carrier collection and to keep resistivity low. Transition between normal to S-shaped like J-V curve is observed at high Si-PEDOT:PSS interface defect density, highlighting the importance of hybrid interface passivation for good device performance. Our simulation work found that an efficiency of 18% can be obtained for a 125 μm thick planar cell. The device can be further improved by incorporating nanostructures, such as Si nanowires for light trapping [4]. This study demonstrates the potential of the back-contact back-junction cell design to achieve high performance and low cost Si/PEDOT:PSS hybrid solar cell.

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Fig. 1 Cross-sectional view of a unit cell of interdigitated back contact Si/PEDOT:PSS hybrid solar cell. 

References

[1]             L. He, Rusli, C. Jiang, H. Wang, and D. Lai, "Simple Approach of Fabricating High Efficiency Si Nanowire/Conductive Polymer Hybrid Solar Cells," IEEE Electron Device Letters, vol. 32, pp. 1406-1408 2011.

[2]             D. Zielke, A. Pazidis, F. Werner, and J. Schmidt, "Organic-silicon heterojunction solar cells on n-type silicon wafers: The BackPEDOT concept," Solar Energy Materials and Solar Cells, vol. 131, pp. 110-116, 2014.

[3]             M. Junghanns, J. Plentz, G. Andrä, A. Gawlik, I. Höger, and F. Falk, "PEDOT:PSS emitters on multicrystalline silicon thin-film absorbers for hybrid solar cells," Applied Physics Letters, vol. 106, p. 083904, 2015.

[4]             J. Wang, H. Wang, A. B. Prakoso, A. S. Togonal, L. Hong, C. Jiang, and Rusli, "High efficiency silicon nanowire/organic hybrid solar cells with two-step surface treatment," Nanoscale, vol. 7, pp. 4559-65, 2015.