Exploiting piezoelectric charge for high performance graded InGaN nanowire solar cells

The effect of piezoelectric charge on the performance of p-GaN/n-InGaN abrupt and graded heterojunction nanowire solar cells is investigated by numerical simulation. In abrupt junctions, piezoelectric charge increases the energy barrier height for hole transport into GaN, resulting in poor overall efficiency. Incorporation of a linearly graded junction improves the performance by removing the valence band barrier. Grading distributes the strain field over a wider region than in an abrupt junction. Both spontaneous and piezoelectric charge boost the efficiency by generating polarization-induced p-type conductivity. A maximum overall efficiency of similar to 21% is predicted considering the effect of polarization charge. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757990]