Quasi-Fermi level splitting and identification of recombination losses from room temperature luminescence in Cu(In1−xGax)Se2 thin films versus optical band gap

摘要: Abstract Photoluminescence (PL) from high-quality Cu(In,Ga)Se2 films has been analyzed at room temperature and under excitation of AM1.5-equivalent photon fluxes. CIGS deposited on glass Mo were front-side passivated with a 50-nm-thick CdS-window layer. From spectral luminescence these their absorption, we have extracted the Bose-term in Planck's generalized law describing emission radiation matter, thus determine splitting quasi-Fermi levels which corresponds to upper limit for maximum achievable open-circuit voltage final devices. The absorption by transmission reflection (integrating sphere) shows each Ga content non-negligible subgap indicating substantial combined density states gap energies almost independent content. At variance shift optical gap, low-energy onset towards higher rise PL yield is comparatively weak and, accordingly, increase Fermi level separation versus band small. low “pinning” signalizes energy irrespective degree alloying. experimentally detected departure points local inhomogeneities terms material composition, metallurgical phases, consequently electronic properties.