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
$ J_{\rm{SC,IQE}} $
> 14 mA/cm
²
, suitable for high-efficiency multijunction cells, while RHJ cells showed diminished
$ J_{\rm{SC,IQE}} $
< 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 (
$V_{\rm{OC}}$
) of 1.292 V with threading dislocation density (TDD) of 1.0 × 10
⁷
cm
⁻²
, a similar
$V_{\rm{OC}}$
value to FJ cells grown lattice-matched on GaAs. In addition, for a high TDD of 2.7 × 10
⁸
cm
⁻²
, RHJ cells had a
$V_{\rm{OC}}$
of 1.223 V, greater than FJs with 10× lower TDD of 2.7 × 10
⁷
cm
⁻²
, which further shows the high dislocation tolerance of n-GaInP. The high
$V_{\rm{OC}}$
, combined with the proposed work to boost IQE, could enable GaInP RHJs on Si for multijunction cell applications.