Effect of Threading Dislocations on GaInP Front- and Rear-Junction Solar Cells Grown on Si

We compare the performance of front-junction (FJ) and rear-heterojunction (RHJ) 1.9 eV GaInP solar cells grown on Si by molecular beam epitaxy. First, time-resolved photoluminescence showed a minority carrier lifetime of 11.7 ns for n -GaInP on Si, indicating a high tolerance to threading dislocations due to the low mobility of minority holes. GaInP solar cells were grown on both GaAs and Si substrates in FJ ( p -type absorber) and RHJ ( n -type absorber) configurations. The internal quantum efficiency (IQE) of FJ cells was identical on GaAs and Si substrates and showed high IQE-derived short-circuit current density <tex-math notation="LaTeX">JSC,IQE</tex-math> > 14 mA/cm 2 , suitable for high-efficiency multijunction cells, while RHJ cells showed diminished <tex-math notation="LaTeX">JSC,IQE</tex-math> < 11 mA/cm 2 due to limited diffusion length and high sensitivity to front-surface recombination. The RHJ cells on Si maintained a high open-circuit voltage ( <tex-math notation="LaTeX">VOC</tex-math> ) of 1.292 V with threading dislocation density (TDD) of 1.0 <tex-math notation="LaTeX">×</tex-math> 10 7 cm −2 , a similar <tex-math notation="LaTeX">VOC</tex-math> value to FJ cells grown lattice-matched on GaAs. In addition, for a high TDD of 2.7 <tex-math notation="LaTeX">×</tex-math> 10 8 cm −2 , RHJ cells had a <tex-math notation="LaTeX">VOC</tex-math> of 1.223 V, greater than FJs with 10 <tex-math notation="LaTeX">×</tex-math> lower TDD of 2.7 <tex-math notation="LaTeX">×</tex-math> 10 7 cm −2 , which further shows the high dislocation tolerance of n-GaInP. The high <tex-math notation="LaTeX">VOC</tex-math> , combined with the proposed work to boost IQE, could enable GaInP RHJs on Si for multijunction cell applications.