40.8% efficient inverted triple-junction solar cell with two independently metamorphic junctions

Abstract

A photovoltaic conversion efficiency of 40.8% at 326 suns concentration is demonstrated in a monolithically grown, triple-junction III–V solar cell structure in which each active junction is composed of an alloy with a different lattice constant chosen to maximize the theoretical efficiency. The semiconductor structure was grown by organometallic vapor phase epitaxy in an inverted configuration with a 1.83 eV Ga.51In.49P top junction lattice-matched to the GaAs substrate, a metamorphic 1.34 eV In.04Ga.96As middle junction, and a metamorphic 0.89 eV In.37Ga.63As bottom junction. The two metamorphic junctions contained approximately 1×105 cm−2 and 2–3×106 cm−2 threading dislocations, respectively.

Implications of low breakdown voltage of component subcells on external quantum efficiency measurements of multijunction solar cells

“…However, this does not provide a satisfactory explanation for a number of reasons, because (1) there is a Villas range where a constant EQE of the Ge BC is measured, (2) there is a Vbias range where measurement artifacts appear (both in the MC and the BC) which are independent of the light bias applied to the MC and TC and (3) the EQE of the MC is correctly measured for V¡,i as < 1.6V despite the BC-limiting light bias condition. Luminescent coupling effects at high Vuas between MC and BC are also discarded as an explanation for the tendency observed in Figure 2, because the operating point of the MC (close to its V oc ) does not significantly change with V¡,i as while measuring the BC [19].…”

“…V br a 1 (2) Accordingly, in order to study the effect of the breakdown voltage on the EQE measurement of the Ge subcell, two different substrates with different doping levels were used to grow the 3JSC structures, namely 4 x 10 17 and 1 x 10 18 cm . As it will be shown later, in this way, the reverse characteristic of the Ge subcell is accordingly modified.…”

“…For instance, the most widespread, commercially available, MJSC is a triple-junction solar cell (3JSC) formed by a GalnP-based top cell (TC) of ~1.9eV, a GalnAs-based middle cell (MC) of ~1.4eV and a Ge bottom cell (BC) of ~0.6eV grown on Ge substrates. In recent years, several 3JSC designs such as metamorphic [1], inverted metamorphic [2], architectures based on dilute nitrides [3] or 3JSCs using bifacial epigrowth [4] have achieved efficiencies higher than 40% by the use of BCs close to 1 eV. MJSC with four junctions have achieved even higher efficiencies by the mechanical bonding of two dual-junction solar cells [5], and in the near future, current 3JSC are expected to achieve higher efficiencies by adding a low-bandgap fourth junction such as a Ge subcell.…”

Design of a lattice-matched III–V–N/Si photovoltaic tandem cell monolithically integrated on silicon substrate

“…Its high energy part is lost by carrier thermalisation. To overcome this limitation, the concept of multi-junction solar cell has been proposed and efficiency over 40% were reported for GaAs based cells (Geisz et al 2008;Ming-Han and Yuh-Renn 2012;Baudrit et al 2008;Baudrit et al 2010;Friedman et al 2010;Green et al 2010;Green et al 2013).…”

Origin of the failed ensemble average rule for the band gaps of disordered nonisovalent semiconductor alloys

“…The properties of the isovalent alloys have been extensively studied. For example, the band gap of the Ga x In 1−x P, which is an ideal material for the solid-state light-emitting diodes and high-efficiency multi-junction solar cells 12,13 , can be tuned by varying the composition and ordering parameters. However, the properties of the nonisovalent alloys are poorly understood.…”