Figure 7.
Shockley–Read Hall lifetimes τn and τp obtained using multiphonon theory as outlined in [86] to obtain the capture coefficients for transitions between the band and localized trap states. The lifetimes are given as a function of the depth of the trap relative to the conduction band edge EC and for the case of a donor-like (solid line) and an acceptor-like defect. From τn and τp an effective lifetime is calculated assuming high-level injection (≈p) via τeff = τn + τp. (b) Sommerfeld factor sA for attractive transitions (e.g. electron is trapped by a positively charged defect) as a function of the low-frequency permittivity εr and for different values of the effective mass meff/m0. Using typical values reported for MAPI (εr = 33.5 [53], meff/m0 = 0.2), the Sommerfeld factor assumes the value approximately 2.2 indicated in the graph as a filled circle. This low value implies a weak influence of attractive versus neutral defect states and therefore a weak shift of the data for donor and acceptor like defects shown in (a). (Online version in colour.)