Recently, a new type of heat pumps based on the thermopotonic (TPX) principles was proposed [1]. The working principle of TPX is an apparent paradox of a light-emitting diode (LED): for each radiatively recombining electron-hole pair a luminescent diode may emit a photon with energy larger than the bandgap of the semiconductor material LED is made of. The excess energy is provided as heat taken under the form of the phonons from the crystal lattice, resulting - for a sufficiently high quantum efficiency (QE) - in refrigerating action of the LED [2], [3]. Introducing the absorber photodiode (PD) in the TPX structure allows to recycle the electrical energy back to the emitter. Also, enclosing both the LED and PD in an optical cavity with a nearly homogeneous refractive index removes the conventionally encountered problem of photons back scattering from the semiconductor/air interface. Thus, the photons no longer need to escape the semiconductor since they are emitted and absorbed within the same semiconductor structure.  This structure essentially represents a three terminal device formed of two diodes, with cathodes that are connected together as a common ground terminal as illustrated in Fig. 1 (left side). Simultaneous measurement of currents through the top (LED) and bottom (PD) terminals allows to determine one of the most obvious parameters quantifying the energy transfer between the emitter and absorber: coupling quantum efficiency (CQE) (Fig.1, right side). CQE approximates the lower boundary of the photon transfer between the component diodes and is defined as ηCQE = I1 / I2, where I1 and I2 are the LED and he PD currents, respectively [4].  Here, the current progress in development of the double diode structures for demonstration of high-power electroluminescent cooling will be reported.  Fig. 1. Vertical cross-section of a double diode structure (left side), typical CQE and I-V curves of the coupled LED and PD (right side).  Acknowledgments: this project has received funding from the Academy of Finland and the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programme (grant agreement No 638173). Facilities and technical support where provided by Micronova Nanofabrication Centre at Aalto University. IR thanks Dr. Tech. Jani Oksanen for fruitful discussions.