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Abstract:

Hybrid lead-halide perovskites are widely used in a variety of optoelectronic applications, including perovskite solar cells (PSCs), perovskite light-emitting diodes (PeLEDs), perovskite photodetectors (PPDs), and scintillators. Recently, it was demonstrated that bulky organic cations (BOCs) can be used as surface passivation agents to fine-tune the dimensionality of lead-halide perovskites, making it possible to tailor their optoelectronic properties and enhance their stability. This special feature has further improved the commercialization potential of perovskite-based optoelectronic devices. In this article, we provide a comprehensive review of the recent progress in low/multidimensional perovskites prepared via BOC treatment and their performance in various optoelectronic devices. We begin by introducing the special features and fundamental properties of lead-halide perovskites with different dimensionalities and the working mechanism of BOC treatments. Thereafter, we separately highlight and discuss the device architecture and performance breakthroughs of BOC-treated perovskites in (i) PSCs, (ii) PeLEDs, and (iii) PPDs and scintillators, emphasizing works published from 2018 till now. For each application, the influence of BOC treatments on device performance and stability is discussed. At the end of this review, we provide our insights on future challenges and commercialization opportunities for BOC-treated perovskites in the field of optoelectronics.

Abstract:

Tin-iodide perovskites are an important group of semiconductors for photovoltaic applications, promising higher intrinsic charge-carrier mobilities and lower toxicity than their lead-based counterparts. Controllable tin vacancy formation and the ensuing hole doping provide interesting opportunities to investigate dynamic intraband transitions of charge carriers in these materials. Here, we present for the first time an experimental implementation of a novel Optical-Pump–IR-Push–THz-Probe spectroscopic technique and demonstrate its suitability to investigate the intraband relaxation dynamics of charge carriers brought into non-equilibrium by an infrared “push” pulse. We observe a push-induced decrease of terahertz conductivity for both chemically- and photodoped FA0.83Cs0.17SnI3 thin films and show that these effects derive from stimulated THz emission. We use this technique to reveal that newly photogenerated charge carriers relax within the bands of FA0.83Cs0.17SnI3 on a sub-picosecond timescale when a large, already fully thermalized (cold) population of charge-carriers is present. Such rapid dissipation of the initial charge-carrier energy suggests that the propensity of tin halide perovskites towards unintentional self-doping resulting from tin vacancy formation makes these materials less suited to implementation in hot-carrier solar cells than their lead-based counterparts.