Scaling Behavior in the Spectral and Power Density Dependent Photovoltaic Response of Hot Polaronic Heterojunctions

Abstract Strongly correlated manganites can be considered as model systems for the study of photovoltaic harvesting of hot polarons that can be excited from the electronically ordered ground state. In order to gain basic understanding of hot polaron harvesting, the deviations of the photovoltaic response of a heterojunction with polaronic absorber from a conventional semiconductor are analyzed. Specifically, the spectral and photon power density dependence of the open circuit voltage U oc and the short circuit current density J sc in heterojunctions consisting of orbital ordered Pr 1‐x Ca x MnO 3 ( x = 0.1, PCMO) thin films epitaxially grown on single crystalline (100) SrTiO 3 (STO) and Nb‐doped (100) SrTiO 3 (STNO) substrates are investigated. The observed behavior is fundamentally different from conventional solar cells, in which U oc is limited by fast carrier relaxation to the band edges. Whereas the spectral and photon power dependence of U oc of conventional semiconductor junctions is well described by the Shockley‐Queisser (SQ) theory, the hot polaron junctions surprisingly show a scaling law behavior of U oc . Such scaling laws otherwise apply to equilibrium order parameters in second‐order phase transitions. It is concluded that its physical origin is the unique dependence of the quasi‐Fermi level splitting on temperature, photon energy, and power density in a hot polaron system.