Perspective on photovoltaic optical power converters

Abstract

Optical wireless power transmission (OWPT) can be used for applications that cannot access traditional power using metal wires. Photovoltaic power-converting III-V semiconductor devices are the core components required for achieving such remote and galvanically isolated power deployments. The development of high-efficiency power converters has already propelled several sensors and probe applications. This growing applied physics field is leveraging the use of ubiquitous laser diode products, now commonly available at various wavelengths. Novel multijunction designs, based on the vertical epitaxial heterostructure architecture devices, have recently allowed fiber-based and free-space applications to quickly progress to higher electrical powers and to benefit from other laser wavelengths. Here, we discuss the perspectives of such multijunction power converters from the viewpoint of realizing additional OWPT deployments and for enabling more probe, sensor, or electronic subsystem power capabilities. The Perspective hence provides a roadmap for devices achieving not only higher conversion efficiency, but also elaborates on the practical aspects necessary to concurrently push the power converters to higher output powers. The photovoltaic multijunction power-converting device is particularly a game-changer for smartly increasing the output voltage and therefore maintaining practical optimal external loads at high laser input powers. Examples of conversion efficiencies above 60% for output powers up to 17.5 W are demonstrated at ∼808 nm in this study, and up to 22 W of output power is obtained with an efficiency of 48.9% at ∼980 nm.

High-Efficiency and High-Power Multijunction InGaAs/InP Photovoltaic Laser Power Converters for 1470 nm

“…The key result measured with the PT10-InGaAs/InP from this study is added as a data point (45) in Figure 2, which shows the updated power converter performance chart built from the results published in the literature [41]. Detailed results from the PT10-InGaAs/InP OPCs are then presented below.…”

“…The InGaAs subcells lattice-matched to InP are expected to contribute ~0.5 V of output voltage each, such as based on previous single-junction measurements [41]. For this study, a PT10 design was selected (vertical multijunction with 10 subcells) in order to achieve an output voltage in the range of ~5 V. The schematic of the PT10-InGaAs/InP heterostructure is depicted in Figure 1a.…”

“…The InP substrate is transparent to the input light and to the InGaAs luminescence, therefore allowing the light reflected [8] from the back side of the device to be recycled [79][80][81][82]. Nevertheless, as described previously [41,58], to realize the required photocurrent matching condition, the structure usually has increasing subcell thicknesses from the top subcell (thinnest) toward the bottom subcell (thickest).…”

“…In addition, in a recent perspective paper, we reviewed the developments of optical power converters (OPCs) , often also referred to as laser power converters (LPCs). The resulting Power Converter Performance Chart [41] clearly highlights that multijunction OPCs are required for obtaining not only high conversion efficiencies, but also high output powers. The research related to photovoltaic devices suggests other potential future device improvements [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67], optical wireless power transmission applications [68][69][70][71][72][73][74], and system design strategies [75][76][77][78].…”

“…The key benefits of this wavelength option include the good availability of laser diodes and the maturity of GaAs-based devices. More recently, ~980 nm has become an interesting wavelength option, because the laser diodes for that range can be strategic (reliability or cost) and due to the novel availability of multijunction OPCs to cover this option [37,38,41]. Another wavelength option is in the 1310 nm region, which also has interesting recent developments [30], and can benefit from the low fiber attenuation for that spectral region.…”