Multijunction Ga0.5In0.5P/GaAs solar cells grown by dynamic hydride vapor phase epitaxy

Abstract

AbstractWe report the development of Ga0.5In0.5P/GaAs monolithic tandem solar cells grown by dynamic hydride vapor phase epitaxy, a III‐V semiconductor growth alternative to metalorganic vapor phase epitaxy with the potential to reduce growth costs. The tandem device consists of 3 components: a 1.88 eV band gap (EG) Ga0.5In0.5P top cell, a p‐Ga0.5In0.5P/n‐GaAs tunnel junction, and a 1.41 eV rear heterojunction GaAs cell. The open circuit voltage (VOC) and fill factor are 2.40 V and 88.4%, respectively, indicative of high material quality. Electroluminescence measurements show that the individual VOC of the top and bottom cell are 1.40 and 1.00 V, respectively, yielding EG‐voltage offsets (WOC) of 0.48 and 0.41 V. The WOC of the top cell is higher because of an unpassivated front surface rather than the bulk material quality. The Ga0.5In0.5P top cell limits the current of this series‐connected device for this reason to a short‐circuit current density (JSC) of 11.16 ± 0.15 mA/cm2 yielding an overall efficiency of 23.7% ± 0.3%. We show through modeling that thinning the emitter will improve the present result, with a clear pathway toward 30% efficiency with the existing material quality. This result is a promising step toward the realization of high‐efficiency III‐V multijunction devices with reduced growth cost.