Monte Carlo analysis of a monolithic interconnected module with a back surface reflector

Abstract

NOTICERecently, the photon Monte Carlo code, RACER-X, was modified to include wavelength dependent absorption coefficients and indices of refraction. This work was done in an effort to increase the code's capabilities to be more applicable to a wider range of problems.These new features make RACER-X useful for analyzing devices like Monolithic Interconnected Modules (MIMs) which have etched surface features and incorporates a back surface reflector (BSR) for spectral controL A series of calculations were perfonned on various MIM structures to determine the impact that surEace features and component reflectivities have on spectraI utilization. The traditionaI concern of "cavity photonics" is replaced with ''intracell photonics" in the MIM design. Like the cavity photonic problem previously discussed [ll, spall changes in optical properties and/or geometry can lead to large changes in spectral utilization. The calculations show that seemingly innocuous surface features (e.g., trenches and grid lines) can significantly reduce the spectral utilization due to the non-normal incident photon flux. Photons that enter the device through a trench edge are rehted onto a trajectory where they will not escape. ?hi leads to a reduction in the number of reflected below bandgap photons that r e m to the mdiator and reduce the specaal utilization. In addition, trenches expose a lateral conduction layer in this particular series of calculations which increase the absorption of above bandgap photons in inactive material.

Monolithic interconnected modules (MIMs) for thermophotovoltaic energy conversion

“…The first surface of the device exposed to incident light is a featureless plane. As a result, light trapping due to the presence of grid fingers , interconnects, or etch trenches common to a standard single-junction MIM [7] is eliminated at the device surface. The planar surface also facilitates the direct deposition or attachment of a first surface filter to enhance transmission of above-bandgap photons and minimize transmission of below-bandgap photons.…”

“…Monte Carlo photonic simulation was conducted and demonstrated that any disturbance from a planar first surface seriously degraded the spectral control performance of the MIM [7]. The interdigitated design, which incorporates v-groove trenches for electrical isolation (as does the conventional MIM design) as well as dovetail trenches for the LCL contact grid, suffered the greatest degradation in optical performance due to this effect.…”

Thermophotovoltaic Spectral Control

“…• The high angular dispersion of incident photons, together with non-specular reflections, lead to the potential for optical frustration [2], (i.e. trapping and multiple internal reflections within the high refraction index layers of the diode/filter).…”

“…grids, busbars, and gaps between diodes) 2. angular and polarization dependent radiator emissivity (i.e., non-Lambertian), 3. angular and polarization dependent front surface filter reflectivity 4. finite separation between radiator and diode which alters the angular dispersion 5. cavity edge leakage or sidewall absorption These non-ideal cavity attributes complicate the photon recuperation. In general, advanced numerical techniques such as Monte Carlo and photon ray tracing are needed to quantify the impact of these processes on TPV performance [2,5].…”

High-performance, lattice-mismatched InGaAs/InP monolithic interconnected modules (MIMs)

“…Recent Monte-Carlo photonic modeling, being presented at this conference [9], suggests that the processing techniques used can have a significant effect on the amount -..-.. -. 'Ofpl~fihs thaf can be-recuperated 'at-tie 'radiator: Four 'areas of particular-interest are the specukddiffused reflectance of the BS~light trapping due to surface features (i.e., isolation trenches), the reflectance of the electrical metailization at the metalsemiconductor interface, and IR absorption in the anti-reflective coating.…”