On January 17th to 22nd, the event SPIE Photonics West 2026 took place in San Francisco, USA. The event is one the biggest conferences on photonics, lasers, and visionary tech. During the Conference 13891 “Physics, Simulation, and Photonic Engineering of Photovoltaic Devices XV” the INFERNO partner Fraunhofer ISE, represented by Dr. Henning Helmers, was one of the presenters of a poster presentation on January 21st, from 6 to 8 PM.
Fraunhofer presented the Paper 13891-32 “InGaAs based strain-balanced multi quantum well 0.66-eV absorber material for thermophotovoltaic applications.” Thermophotovoltaic cells receive increasing interest, especially for applications in energy storage for fluctuating renewable energy sources and in waste heat recovery systems. Especially lower temperature emitters require low bandgap absorber materials. For the quaternary InGaAsP material system grown lattice-matched on InP, In0.53Ga0.47As defines the lower boundary for the semiconductor bandgap at 0.74 eV. Absorber materials with even lower effective bandgap can be achieved following the strain-balanced multi quantum well approach.
In this work, we explore the use of In0.65Ga0.35As quantum well absorbers cladded by InGaAs barriers in varying composition and thickness, targeting ideal strain balancing. We present results from material development using a MOVPE planetary reactor, as well as first experimental results of actual TPV cells realized using this approach. First functional cells were realized with 10 and 20 quantum wells, each featuring an absorber thickness of 12 nm, resulting in effective bandgaps around 0.66 eV.
