Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition.
Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due to their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates to achieve monolithic integration of solar cell materials that are not lattice-matched. Here, we report the first realization of nanowire-on-Si tandem cells with the observation of voltage addition of the GaAs nanowire top cell and the Si bottom cell with an open circuit voltage of 0.956 V and an efficiency of 11.4%. Our simulation showed that the current-matching condition plays an important role in the overall efficiency. Furthermore, we characterized GaAs nanowire arrays grown on lattice-mismatched Si substrates and estimated the carrier density using photoluminescence. A low-resistance connecting junction was obtained using n(+)-GaAs/p(+)-Si heterojunction. Finally, we demonstrated tandem solar cells based on top GaAs nanowire array solar cells grown on bottom planar Si solar cells. The reported nanowire-on-Si tandem cell opens up great opportunities for high-efficiency, low-cost multijunction solar cells.
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Maoqing
M
Yao
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Sen
S
Cong
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Shermin
S
Arab
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Ningfeng
N
Huang
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Michelle L
ML
Povinelli
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Stephen B
SB
Cronin
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
P Daniel
PD
Dapkus
Ming Hsieh Department of Electrical Engineering, ‡Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States.
Chongwu
C
Zhou
GaAs-nanowire-on-Si; Tandem solar cell; current matching; doping characterization; heterojunction; voltage addition