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Efficient silicon solar cells with dopant-free asymmetric heterocontacts

Efficient-silicon-solar-cells-with-dopant-free-asymmetric-heterocontactsLight JV characteristic and schematic of the dopant-free asymmetric heterocontact (DASH) silicon solar cell showing a conversion efficiency of 19.4%, with a high Voc above 710 mV, has been achieved at the proof-of-concept stage. TCO refers to a Transparent Conductive Oxide stack.

Scientific Achievement
Demonstration of efficient crystalline silicon solar cells without the use of doped-silicon layers or regions.

Significance and Impact
Commercially available crystalline silicon solar cells utilize doped-silicon layers or regions to separate photo-excited carriers and hence deliver power. This approach demonstrates that high efficiencies can be achieved using metal oxide and alkali metal fluoride as dopant-free carrier-selective contacts overcoming a number of fundamental and practical limitations.

Research Details

  • LiFx/Al and MoOx heterocontacts are utilized due to their significant asymmetry in work function (2.8 eV vs 5.7 eV) which assists in carrier separation at the two surfaces.
  • Thin passivating hydrogenated amorphous silicon layers are implemented under the selective layers to enhance the voltage.
  • These heterocontacts are integrated into a simplified DASH cell—the first-of-its-kind to demonstrate efficiencies competitive with conventional processes.

J. Bullock, M. Hettick, J. Geissbühler, A. J. Ong, T. Allen, C. M. Sutter-Fella, T. Chen, H. Ota, E. W. Schaler, S. De Wolf, C. Ballif, A. Cuevas and A. Javey, "Efficient silicon solar cells with dopant-free asymmetric heterocontacts",  Nature Energy, 15031 (2016) doi:10.1038/nenergy.2015.31