Toward Hot Carrier Extraction in Intervalley Photovoltaic Devices

Abstract

InGaAs heterostructures have demonstrated the means to maintain high energy '"hot" carrier behavior under practical operating conditions via transfer to upper valleys of the band structure, potentially decreasing thermalization losses in solar cells if a suitable extraction mechanism is developed. A set of four InGaAs heterostructures with altered n + top layers enable comparative analysis of the current density−voltage characterization and the relationship to the band and valley alignments. This reveals that the barriers to extraction are introduced by the challenges of real space transfer between upper valleys of different materials rather than an energy level mismatch at the top heterojunction.

Strong Dimensional and Structural Dependencies of Hot Carrier Effects in InGaAs Nanowires: Implications for Photovoltaic Solar Cells

“…16 Recently, it has been shown that InGaAs/InAlAs heterostructured designs have promising applications in valley-photovoltaic solar cells. 33,34 However, the NW design of such compounds exhibit polytypism (intermixing of zinc-blende and wurtzite crystals) commonly observed in most III−V semiconductor NWs. 35,36 Our studies are enabled by realizing high-uniformity arrays of selective-area grown (SAG) InGaAs NWs passivated by thin epitaxial InAlAs shells, where wide tunability in size dimension (NW diameter) is achieved by accurately tuning the geometry of the SAG pattern.…”

“…InGaAs NWs are among the most appealing candidate materials due to their tunable bandgap, especially toward 0.7 eV, which is the optimum bandgap energy of HCSCs with a relatively small thermalization coefficient (50 W/(K·cm 2 )), high carrier mobility, and high absorption coefficient . Recently, it has been shown that InGaAs/InAlAs heterostructured designs have promising applications in valley-photovoltaic solar cells. , However, the NW design of such compounds exhibit polytypism (intermixing of zinc-blende and wurtzite crystals) commonly observed in most III–V semiconductor NWs. , Our studies are enabled by realizing high-uniformity arrays of selective-area grown (SAG) InGaAs NWs passivated by thin epitaxial InAlAs shells, where wide tunability in size dimension (NW diameter) is achieved by accurately tuning the geometry of the SAG pattern. The hot carrier properties of the NW arrays are assessed by photoluminescence (PL) spectroscopy, and the temperature of hot carriers is determined by analyzing the PL spectra using the generalized Planck’s radiation law while taking the diameter-dependent photoabsorption of individual arrays into account.…”