Detection of Nonradiative Recombination Centers in GaPN (N:0.105%) by Below‐Gap Excitation Light

Investigation on cascade photo‐excitation via intermediate band (IB) is promising for improving the efficiency of IB‐type solar cells (IBSCs). Increasing nitrogen (N) concentration in GaP changes an ensemble of discrete N–N pair levels to form the IB as well as introducing defect levels acting as nonradiative recombination (NRR) centers. In continuation of detecting NRR centers in GaP1−xNx (x > 0.5%), a study is made for the lower N concentration region of 0.105% to understand an original formation of defect levels and their properties. Elimination of temperature quenching by immersing the sample into liquid nitrogen reveals a distribution of NRR centers inside the forbidden energy gap and the shift of Fermi energy depending on above‐gap excitation (AGE) density. Profound understanding of IB and defects of GaP1−xNx leads to a proper optimization of IBSCs. The two‐wavelength excited photoluminescence (TWEPL) method reveals the presence of nonradiative recombination (NRR) centers in GaPN (N:0.105%). Different contribution of one and two‐level models explains the energy dependence of below‐gap excitation (BGE). The shift of Fermi‐energy in the mid‐gap level according to above‐gap excitation (AGE) photon number density plays an important role in the interpretation of NRR processes, which must be minimized for improving intermediate band solar cells (IBSCs).