In_0.53Ga_0.47As/InP conventional and inverted thermophotovoltaic cells with back surface reflector Available to Purchase

Characteristics of conventional and inverted InGaAs/InP thermophotovoltaic (TPV) cells with a back surface reflector (BSR) fabricated on electrically active n‐type InP substrates are presented. Thermophotovoltaic cells based on lattice matched InP‐In_0.53Ga_0.47As heterostructures were fabricated with the use of LPE and Zn,P diffusion technologies.

In the p‐n TPV cells (conventional type, spectral range 600÷1800 nm) with a frontal p‐InGaAs layer, BSR was made on a n‐InP substrate. In the n‐p structure (inverted type, spectral range1000–1800 nm) with a frontal bulk n‐InP‐window‐substrate, BSR was formed on a p‐InGaAs layer. Antireflection coating (ARC) on the frontal cell surface consists of ZnS/MgF₂ layers.

Results of investigation of sub‐bangap photons reflection from InP substrates with a backside MgF₂/Au mirror in the range of 1800÷2000nm are described. The reflection of BSR for InP samples with the doping level in the range of 1×10¹⁷÷6×10¹⁸cm⁻³ evidenced a weak dependence on their thickness and doping level. A reflection of 86÷90% has been measured for substrates 100μm thick and 80% for ones 400μm thick with ARC.

Study of sub‐bandgap photon reflection of p‐InGaAs (Zn,P) layers with surface concentration of 1÷3×10¹⁹cm⁻³ has been also carried out. A reflection of 68÷77% for 2÷4μm layers with “hybrid” (ohmic contact plus mirror) back‐surface reflector consisted of deposited Cr/Au layers was measured.

It was found, that p‐n and n‐p thermophotovoltaic 1×1cm² cells with identical grid design reveal similar parameters for up to 1A/cm² current density (V_OC=465mV and FF=64%) and the 76÷80% reflection of the sub‐bandgap photons for wavelengths longer than 1.86μm.

The developed inverted InGaAs TPV cells have been tested under illumination of silicon carbide high temperature emitter. The photocurrent density J_sc=7A/cm², open circuit voltage V_oc=0.476V and fill factor FF=0.691 have been measured in the inverted (without BSR) InGaAs cell under SiC emitter heated to the temperature of about 1550°C.

Both types of devices can successfully be used as TPV cells for conversion of radiation in the range of 1500–1900K, with 14–15% efficiency.