Method for characterizing bulk recombination using photoinduced absorption

The influence of reaction order and trap-assisted recombination on continuous-wave photoinduced absorption measurements is clarified through analytical calculations and numerical simulations. The results reveal the characteristic influence of different trap distributions and enable distinguishing between shallow exponential and Gaussian distributions and systems dominated by direct recombination by analyzing the temperature dependence of the in-phase and quadrature signals. The identifying features are the intensity dependence of the in-phase at high intensity, PA_I∝I^γHI, and the frequency dependence of the quadrature at low frequency, PA_Q∝ω^γLF. For direct recombination, γ_HI and γ_LF are temperature independent, and for an exponential distribution, they depend on the characteristic energy E_ch as γ_HI=1/(1+E_ch/kT) and γ_LF=kT/E_ch, while a Gaussian distribution shows γ_HI and γ_LF as functions of I and ω, respectively.