Optimization of In_0.68Ga_0.32As Thermophotovoltaic Device Grown on Compositionally Nonmonotonically Graded InAsP Buffer by Metal–Organic Chemical Vapor Deposition

Abstract

An In0.68Ga0.32As thermophotovoltaic (TPV) cell on a compositionally nonmonotonically graded InAsP buffer with a band gap energy of 0.60 eV grown by metal–organic chemical vapor deposition (MOCVD) has been fabricated. The performance of the TPV device was greatly improved with optimized material growth, the use of an absorption layer of suitable width, and appropriate TiO2/SiO2 antireflective coating design. Under standard AM1.5G spectra, the open circuit voltage (V oc) increases from 0.19 to 0.23 V, the short-circuit current density (J sc) increases from 43 to 56 mA/cm2, and the conversion efficiency increases from 5.31 to 8.06%. By illumination at a high intensity of 50 suns, a high conversion efficiency of 12.3% with a V oc of 0.35 V is reached.

A Review on Thermophotovoltaic Cell and Its Applications in Energy Conversion: Issues and Recommendations

“…The effect of different buffer structures, such as a single buffer layer, compositionally graded buffer layers and superlattice buffer layers, were investigated [156,[167][168][169]. A lattice mismatch of ∼1.2% was introduced between In 0.68 Ga 0.32 As and a compositionally nonmonotonically graded InAsP buffer layer (14 layer grades) [155,156]. On the other hand, Hudait et al [85,91] has grown In 0.69 Ga 0.31 As using the MBE method and reported a 1.1% lattice-mismatch between the device layer and the InP substrate.…”

“…The vast majority of lattice-matched and mismatched InGaAs TPV structure reported the use of AuGe and Ti/Au as front metal contact and Au and TiAu as back metal contact [ 85 , 102 , 164 ] to produce an ohmic contact. Tan et al [ 155 ] used Ni/AuGe/Ni/Au metallization scheme for n-type ohmic contact, and Pd/Zn/Pd/Au metallization was used for p-type ohmic contact. Recently, Kao et al [ 132 ] reported the utilization of AuGe/Au metallization for n-type InGaAs layer.…”

“…Most of the literature reported a very thin layer of emitter layer from 0.1 to 0.3 µm [ 155 ]. Thinner highly doped emitter is able to produce lower resistance depending on the metal contact and able to generate a feasible electric field with the base layer.…”

“…The R s value can be further minimized by optimizing the physical parameters (doping and thickness) of the entire structure. Ming et al [ 155 ] presented an improvement in TPV device for an In 0.68 Ga 0.32 As cell with optimized material growth, suitable absorber thickness of 2.8 µm as well as TiO 2 /SiO 2 ARC with 2.1 µm InAsP buffer layer. Such enhancement has increased the from 0.19 to 0.23 V, the from 43 to 56 mA/cm 2 , and the conversion efficiency from 5.31 to 8.06% under AM 1.5 test condition.…”

“…Recently, studies used an InGaAs cell in multi-junction such as GaInP/GaAs/InGaAs [103], and tandem cells such as GaAs/InGaAs [154], which aim to increase the total efficiency and to extend the power harvesting into the mid-infrared wavelengths. Several studies reported the crystal defects of lattice mismatch InGaAs cells for bandgap from 0.55 to 0.6 eV [155], characterization of the cell performances and optimization of the structure design [156][157][158][159].…”