Studying the carrier recombination process in MAPb(Br1−yIy)3 single crystals (SCs) is important for its application in the optoelectronic field. In this work, a series of MAPb(Br1−yIy)3 SCs with varied Br/I compositions have been studied. Steady-state photoluminescence (PL) spectra, time-resolved photoluminescence (TRPL) spectra and time-resolved microwave photoconductivity (TRMC) were used to understand the radiative and non-radiative recombination processes of MAPb(Br1−yIy)3 SCs. By comparing the dynamics of TRPL and TRMC, we conclude that the dynamics of TRPL is dominated by the electron trapping process, which is in accordance with the fast decay component of TRMC kinetics, whereas the slower decay component in TRMC is dominated by the hole trapping process. Moreover, we find both the electron and hole trapping rates in mixed-halide perovskite MAPb(Br1−yIy)3 (0 < y < 1) SCs are higher than that of mono-halide perovskite MAPbBr3 SCs and MAPbI3 SCs. This suggests mixed-halide crystals could introduce additional electron and hole trapping densities, which could be related to the fluctuation of Br/I compositions in the crystals. This work is helpful for understanding carrier recombination process in mixed-halide perovskite SCs.

Antimony selenide (Sb2Se3) is a promising low-cost and environmental-friendly semiconductor photovoltaic material. The power conversion efficiency of Sb2Se3 solar cells has been improved to be 10% in the past few years. The carrier recombination transfer dynamics are significant factors that impact the Sb2Se3 solar cells efficiency. In this work, carrier recombination on the Sb2Se3 surface and carrier transfer dynamics at the CdS/Sb2Se3 heterojunction interface are systematically investigated by surface transient reflectance. According to the evolution of relative reflectance change "?R" /"R" , the carrier thermalization and band gap renormalization time of Sb2Se3 were determined ranging from 0.2 to 0.5 ps, and carrier cooling time was estimated to be about 3?4 ps. Our results also firstly demonstrate that both free electron and shallow-trapped electron transfer occur at the Sb2Se3/CdS interface after photo excitation. The shallow-trapped electron transfer efficiency was calculated in the range of 30% to 70%, determined by the relaxation of shallow trapped electron to deep energy level trap state s. Our results provide a methodology for interpreting transient reflectance of Sb2Se3, and enhances the understanding on carrier kinetics at Sb2Se3 surface and Sb2Se3/CdS interface.

Understanding carrier recombination processes in MAPb(Br x Cl1–x )3 crystals is essential for their photoelectrical applications. In this work, carrier recombination dynamics in MAPb(Br x Cl1–x )3 single crystals were studied by steady-state photoluminescence (PL), time-resolved photoluminescence (TRPL), and time-resolved microwave photoconductivity (TRMC). By comparing TRPL and TRMC, we find TRPL of MAPb(Br x Cl1–x )3 (x < 0.98) single crystals is dominated by a hole trapping process while the long-lived component of TRMC is dominated by an electron trapping process. We also find both electron and hole trapping rates of MAPb(Br x Cl1−x )3 (x < 0.98) crystals decrease with an increase in Br content. A temperature-dependent PL study shows there are shallow trap states besides the deep level trap states in the MAPb(Br0.82Cl0.18)3 crystal. The activation energy for holes in shallow trap states detrapped into the valence band is ∼0.1 eV, while the activation energy for free holes to be trapped into deep trap states is ∼0.4 eV. This work provides insight into carrier recombination processes in MAPb(Br x Cl1–x )3 single crystals.

Sb2Se3 has recently emerged as a promising material for optic-electronic applications. In this work, trapped carrier recombination in Sb2Se3 was investigated by joint use of time-resolved microwave conductivity (TRMC) and photoluminescence (PL) spectroscopy. trapped carrier thermal excitation into the continuous band was observed in TRMC kinetics. Based on the exponential band tail model, the depth of the trap state, where trapped carriers are released into a continuous band, was estimated to range from 33.0 meV to 110.0 meV at room temperature. Temperature-varying TRMC and PL were further employed to study the influence of temperature on the trapped carrier recombination. Negative thermal quenchings of PL intensity and quantity of thermal emission carriers were observed and can be well explained by the thermal excitation of deep trapped carriers into shallow trap states and the continuous band. Two thermal activation energies of 12.5 meV and 304.0 meV were also revealed. This work is helpful for understanding the trapped carrier recombination process in polycrystalline Sb2Se3 film.