Sub-50 picosecond to microsecond carrier transport dynamics in pentacene thin films

Abstract

Carrier transport dynamics from sub-50 ps to ∼μs over five temporal decades in pentacene films was studied by transient photoconductivity. The behavior of the temperature independent photocurrent peak suggests that the photogenerated carriers exhibit pre-trapping transport in extended states upon pulsed laser excitation. From 300 ps to ∼30 ns, the carriers thermalize and fall into shallow band tail states, and multiple-trapping and release transport dominates. From ∼30 ns to ∼μs, the weak temperature dependence of power-law photocurrent decay and the linear relation of logarithmic photocurrent with T−1/4 suggest a variable range hopping transport in deep trap states.

Are solution processed CsPbI3 perovskite nanocrystalline films similar to traditional crystalline semiconductors?

“…1d, by integrating a CsPbI 3 nanocrystal thin film photoconductor into transmission line architecture as a high-speed waveguide, the carrier drift dynamics can be investigated in photoconductors in operando with a sub-25 ps time resolution by the UPCS. The UPCS is superior to the Auston photoconductive switch technique since it has a much higher temporal resolution and can characterize various materials systems (21)(22)(23). A detailed nanocrystal film morphology and experimental configuration can be found in Supplementary Methods and Supplementary Fig.…”

In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions

“…The UPCS experimental setup is demonstrated in Fig. 1 and is superior in temporal, energy resolution, and in situ measurement ability to previously reported ultrafast techniques in other semiconductor systems utilizing organic semiconductors 27,28 semiconductors 29 , and 2D layered semiconductors [30][31][32] . In contrast to ultrafast optical spectroscopies, the UPCS studies the ultrafast carrier dynamics in situ devices by directly collecting carriers as a current, under diverse tunable experimental conditions, such as temperature, excitation photon energy, photon density under linear and nonlinear excitations, and an electrical field.…”

Trap-Filling Magnetoconductance as an Initialization and Readout Mechanism of Triplet Exciton Spins

“…35−40 It is also beneficial for the crystalline layer to be able to form trap sites, as these have been shown to be critical in triplet−charge MC experiments in other materials. 41−43 We chose polycrystalline pentacene as our model system, as it exhibits both the large charge carrier mobilities 44,45 that would be needed for responsive device structures and extremely efficient singlet fission, whereby 2 triplet excitons are produced for every absorbed photon. 46−50 Figure 1 shows the device layers and characteristics under normal operating conditions.…”

“…In order to observe an MC effect from triplet–charge interactions, devices were fabricated with the goal of generating a significant triplet density, but also only a single charge carrier type to limit the influence of polaron pairs. − It is also beneficial for the crystalline layer to be able to form trap sites, as these have been shown to be critical in triplet–charge MC experiments in other materials. − We chose polycrystalline pentacene as our model system, as it exhibits both the large charge carrier mobilities , that would be needed for responsive device structures and extremely efficient singlet fission, whereby 2 triplet excitons are produced for every absorbed photon. − …”