Detection of Nonradiative Recombination Centers in GaPN by Combining Two‐Wavelength Excited Photoluminescence and Time‐Resolved Photoluminescence

• Published in: physica status solidi (b) Vol. 258; no. 11
• Main Authors: Ferdous, Sanjida, Iwai, Hiroki, Kamata, Norihiko, Yaguchi, Hiroyuki, Yagi, Shuhei
• Format: Journal Article
• Language: English
• Published: 01-11-2021
• Subjects: below-gap excitation; defect level; GaPN; intermediate band; nonradiative recombination
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202100119

Presence and influence of nonradiative recombination (NRR) centers in an intermediate band (IB)‐type material, GaP1–xNx (x=0.75%), are studied by two‐wavelength excited photoluminescence (TWEPL) method and time‐resolved photoluminescence (TRPL) measurement at 77 K. With the use of below‐gap excitation (BGE) light in addition to an above‐gap excitation (AGE), the PL peak intensity is found to increase which indicates the presence of NRR centers and a secondary excitation from the IB to conduction band (CB). Depending on the effect of different BGE energies, an energy diagram on the distribution of NRR centers and NRR process is interpreted. The saturation of PL increase is attributed to the trap‐filling effect in NRR centers, which allows us to modify the rate equation. The NRR parameters are evaluated by a qualitative simulation of the modified rate equations of one‐level model together with the lifetime determined by TRPL. In continuation of evaluating NRR parameters by rate equation analysis, the addition of TRPL measurement improves accuracy and approaches the determination of NRR parameters. A successful characterization of NRR centers leads to a proper optimization of IB‐type solar cells (IBSCs).
The presence of nonradiative recombination (NRR) centers in intermediate band (IB)‐type materials reduces the efficiency of IB‐type solar cells (IBSCs). The detection of NRR centers by two‐wavelength excited photoluminescence (TWEPL) method and the determination of NRR parameters by time‐resolved photoluminescence (TRPL) measurements and rate equation analysis can help in proper optimization of IBSCs.