Phonon Tuning and Recycling in Photonic Energy Conversion: Atomic-Structure Metrics and Examples

[摘要] Phonon generation in photonic energy conversions is inevitable and till now thesephonons have been removed as heat to achieve stable operation. In this study, throughvarious phonon-assisted transition processes, we propose recycling these phonons thusreducing the heat losses. This phonon recycling increases the energy conversion efficiencyand reduces the cooling load and its associated energy consumption.This theoretical work is done through the fundamentals pertaining to the atomiclevelcarrier kinetics and the structural metrics of the phonon recycling in photonics.The photonic systems considered are the ion-doped laser, amorphous-silicon solarphotovoltaic, and potential-barrier integrated light emitting diode. First the carriers(phonon, electron and photon) interaction kinetics in the anti-Stokes cooling of solidsis analyzed starting with the Fermi golden rule applied to the weak photon-electronphononcouplings. Then the influence of phonons (equilibrium and nonequilibrium)is established in the related emission, transport and absorption transitions. Finallythese are used to optimize the phonon-assisted processes, and improve process performance.Ab-initio simulations are used to guide and complement the theoretical treatments.Based on the harmonic oscillator assumption, a general guide is proposed forselection of the optimal host glass constituents for laser cooling. Using Li, Al, and Nabonds with F gives the largest cooling rate improvement up to 200 % over the currentlyused blends. It is predicted that the proposed phonon-assisted photon-absorbing(cooling) layer in ion-doped lasers carries away up to 35 % of the generated phononas spontaneous photon emission, thus improving the laser portability. The low phononenergy Sn alloying proposed for the amorphous silicon solar photovoltaic, is predictedto enhance the current generation by up to 11 %. The integrated, potential-barrierlayer proposed for recycling the phonons generated by nonradiative recombinationprocesses in light emitting diodes, absorbs multiple phonons and is driven by externalpotential. We predict up to 30 % phonon recycling for a barrier height of 0.28 eV.In all examples, efficiency gains are predicted from the proposed phonon recycling.This study is an atomic-level oriented contribution to the thermal management (andits effects on efficiency) of energy conversion devices.

[发布机构] University of Michigan

[效力级别] Mechanical Engineering

[关键词] Phonon Tuning and Recycling in Photonic Energy Conversion;Mechanical Engineering;Engineering;Mechanical Engineering