Long-Range Interfacial Charge Carrier Trapping in Halide Perovskite-C₆₀ and Halide Perovskite-TiO₂ Donor–Acceptor Films

Abstract

Interfacial electron transfer across perovskite-electron acceptor heterojunctions plays a significant role in the power-conversion efficiency of perovskite solar cells. Thus, electron donor−acceptor thin films of halide perovskite nanocrystals receive considerable attention. Nevertheless, understanding and optimizing distance-and thickness-dependent electron transfer in perovskite-electron acceptor heterojunctions are important. We reveal the distance-dependent and diffusion-controlled interfacial electron transfer across donor−acceptor heterojunction films formed by formamidinium or cesium lead bromide (FAPbBr 3 /CsPbBr 3 ) perovskite nanocrystals with TiO 2 /C 60 . Self-assembled nanocrystal films prepared from FAPbBr 3 show a longer photoluminescence lifetime than a solution, showing a long-range carrier migration. The acceptors quench the photoluminescence intensity but not the lifetime in a solution, revealing a static electron transfer. Conversely, the electron transfer in the films changes from dynamic to static by moving toward the donor−acceptor interface. While radiative recombination dominates the electron transfer at 800 μm or farther, the acceptors scavenge the photogenerated carriers within 100 μm. This research highlights the significance of interfacial electron transfer in perovskite films.

Spatial Heterogeneity of n-Phases Leads to Different Photophysical Properties in Quasi-Two-Dimensional Methylammonium Lead Bromide Perovskite

“…The kinetics of the PL consists of three decay components with different time constants: short (4 ns), medium (20–24 ns), and long (95–105 ns). For an explanation of the slow component, we can exclude contributions originating from carrier diffusion or carrier trapping as the lifetimes of these processes are much longer (>500 ns) than the time constants playing a role in our observations. − The short component is attributed to the carrier recombination in the low- n -phase region (R1). As the R1 region contains more defect states, the band-to-band radiative exciton recombination is accompanied by a very fast defect-mediated nonradiative carrier recombination.…”

Mechano-optical Modulation of Excitons and Carrier Recombination in Self-Assembled Halide Perovskite Quantum Dots

“…Also, the long PL lifetime values of the films [27 ns for the blue-emitting film (Figure A) and 550 ns for the green-emitting film (Figure C)] compared to an isolated PQD [2.6 ns, Figure H (iii)] suggest the stability of photogenerated charge carriers in the weakly quantum-confined self-assemblies. However, the unusually long PL lifetime values (>500 ns) are unlikely associated with delayed exciton recombination. , Thus, we consider the delayed PL to result from radiative recombination of freely diffusing and detrapped charge carriers. − Chirvony et al. demonstrated exciton migration in a MAPbBr 3 nanocrystal thin film. , They considered charge carrier storage in deep traps and nonquenching shallow traps followed by detrapping-induced delayed emission.…”

Efficient charge transfer from organometal lead halide perovskite nanocrystals to free base meso-tetraphenylporphyrins

“…The constant fluorescence lifetime, along with a reduction in the number of emitted photons with an increasing amount of quencher, indicates that the excited state of the PNCs has been statically quenched by TPP. 39 a ,40 Meanwhile, the remaining fluorescence at a specific concentration of TPP indicates that the MAPbX 3 PNCs have a trace of unadsorbed TPP. In other words, it can be assumed that the continuous reduction in the quantum efficiency of the nanocomposites without any significant change in lifetime indicates the adsorption of MAPbX 3 PNCs onto the organic molecules.…”

“…Sargent et al 35 reported the improved photocurrent response and stability of solar cells related to C 60 -layered perovskites, which corresponds to the removal of grain boundaries and surface defect passivation in perovskites by C 60 . Electron transport from perovskite to mesoporous titanium dioxide was studied by Gratzel et al 36 An earlier study explored the transfer of electrons from donor PNCs to classical acceptors such as TiO 2 , 37 perylenes, 38 fullerenes, 39,40 benzoquinone, 41 and carbon nanotubes. 42 In this context, Tang et al 43 used a diammonium porphyrin to study the charge transfer dynamics in CsPbBr 3 nanocrystals.…”