No abstract

Inverted metamorphic solar cells play an important role in the field of photovoltaics, because it can directly grow stacked tandem junctions with different bandgaps according to the spectrum. We have found that the four‐junction AlGaInP/AlGaAs/InGaAs/InGaAs solar cells with the bandgap of 1.96/1.55/1.17/0.83 eV on the basis of the inverted metamorphic three‐junction AlGaInP/AlGaAs/InGaAs materials will cause a serious decrease in short‐circuit current density but with a normal open‐circuit voltage. The sharp decrease in short‐circuit current density is not attributed to the mismatched buffers dislocations penetrating into the active region of the InGaAs subcells but resulted from the minority carrier recombination due to defects in the AlGaInP subcell, which is observed directly from transmission electron microscopy, external quantum efficiency, electroluminescence, and secondary ion mass spectrometry measurements. The process of growing AlGaInP materials by metal–organic chemical vapor deposition easily introduces Al‐O deep‐level defects, resulting in the poor collection of minority carriers in AlGaInP materials. After improving the growth conditions of AlGaInP materials, a four‐junction solar cell with a photoelectric conversion efficiency of 34.9% and an open‐circuit voltage of 3.53 V was obtained.

We used printed electronics technology to print silver paste (SP) on n-GaAs as an electrode replacing conventional alloy electrodes to simplify the fabrication process of solar cell and to reduce cost. The linear transmission line model was used to characterize the performances of SP/semiconductor ohmic contact at different annealing temperatures. The lowest specific contact resistance between SP and n-GaAs of 1.8 × 10−4 Ω cm2 was achieved after annealing at 560 °C, which indicates the appropriate annealing temperature can not only ensure the close contact of silver particles, but also reduce the barrier height of metals and semiconductors to a certain extent. On the basis of these results, n-GaAs with an SP electrode can be promisingly applied to realize highly efficient and simple-manufacturing III–V solar cells.