| Phonon generation in photonic energy conversions is inevitable and till now these phonons have been removed as heat to achieve stable operation. In this study, through various phonon-assisted transition processes, we propose recycling these phonons thus reducing the heat losses. This phonon recycling increases the energy conversion efficiency and reduces the cooling load and its associated energy consumption.;This theoretical work is done through the fundamentals pertaining to the atomic-level carrier kinetics and the structural metrics of the phonon recycling in photonics. The photonic systems considered are the ion-doped laser, amorphous-silicon solar photovoltaic, and potential-barrier integrated light emitting diode. First the carriers (phonon, electron and photon) interaction kinetics in the anti-Stokes cooling of solids is analyzed starting with the Fermi golden rule applied to the weak photon-electron-phonon couplings. Then the influence of phonons (equilibrium and nonequilibrium) is established in the related emission, transport and absorption transitions. Finally these 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 for selection of the optimal host glass constituents for laser cooling. Using Li, Al, and Na bonds with F gives the largest cooling rate improvement up to 200 % over the currently used 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 phonon as spontaneous photon emission, thus improving the laser portability. The low phonon energy Sn alloying proposed for the amorphous silicon solar photovoltaic, is predicted to enhance the current generation by up to 11 %. The integrated, potential-barrier layer proposed for recycling the phonons generated by nonradiative recombination processes in light emitting diodes, absorbs multiple phonons and is driven by external potential. 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 (and its effects on efficiency) of energy conversion devices. |
