Observation of the Transient Vertical Currents in Quasi-2D Perovskites

The interelectrode transportation of photoinduced carriers plays a crucial role in the efficient charge collection process of optoelectronic devices such as solar cells. Although the dynamics of photoinduced carrier transport and recombination in solar cells have been extensively studied, direct measurement of vertical transient currents remains a major challenge. Here, we have established a correlation between the transient photocurrent in Quasi-2D perovskite films and its terahertz radiation based on the dipole radiation model. By selectively exciting distinct n-phases in BA 2 MA n –1 Pb n I n +1 Ruddlesden–Popper perovskite films, we disentangle the photo-Dember current from the interphase charge transfer current, revealing their spatiotemporal competition. The ∼1.5 times enhanced THz emission directly links vertical transport efficiency to crystallinity. Notably, the polarity inversion of THz signals under high-energy excitation identifies reversed charge transfer directions at heterojunctions. Our findings establish the THz emission as a powerful tool for vertical transport detection.