Engineering the Exciton Dissociation in Quantum‐Confined 2D CsPbBr₃ Nanosheet Films

Abstract

Recent years have witnessed a rapid development of all-inorganic halide perovskite in optoelectronic devices. Ultrathin 2D CsPbBr 3 nanosheets (NSs)with large lateral dimensions have demonstrated exceptional photophysical properties because of their analogous exciton electronic structure to quantum wells. Despite the incredible progress on device performance, the photophysics and carrier transportation parameters of quantum-confined CsPbBr 3 NSs are lacking, and the fundamental understanding of the exciton dissociation mechanism is far less developed. Here, a ligands rearrangement mechanism is proposed to explain why annealed NS films have an increased charge transfer rate and a decreased exciton binding energy and lifetime, prompting tunneling as a dominant way of exciton dissociation to separate photogenerated excitons between neighboring NSs. This facile but efficient method provides a new insight to manipulate perovskite nanocrystals coupling. Moreover, ultrathin 2D CsPbBr 3 NS film is demonstrated to have a enhanced absorption cross section and high carrier mobility of 77.9 cm 2 V −1 s −1 , contributing to its high responsivity of 0.53 A W −1 . The photodetector has a long-term stability up to three months, which are responsible for reliable perovskite-based device performance.

Achieving long-term water stability and strong exciton–photon coupling in CsPbBr3 quantum dots via MOF encapsulation

“…Due to the larger volume of Pb atoms and the crystallization of CsPbBr 3 within the pores, the volume of the micropores becomes occupied, leading to a decrease in adsorption capacity. Brunauer–Emmett–Teller (BET) surface area of UiO‐66 estimated from the isotherm is 1,510 m 2 /g, similar to that reported previously for defective UiO‐66 [64]. After the incorporation of Pb 2+ ions and the formation of pore‐confined CsPbBr 3 , the BET surface areas decrease to 970 m 2 /g and 320 m 2 /g, respectively.…”

“…In the low‐temperature range (4–150 K), the PL peak energy shows a linear increase, which is well described by the thermal expansion term. The extracted coefficient C th = is significantly smaller than that typically reported for CsPbBr 3 [64], [67], [68], suggesting that the thermal effects on lattice expansion are suppressed by the confinement within the UiO‐66 framework. At higher temperatures ( T > 150 K), the slope of the PL peak energy curve begins to gradually decrease.…”

Excellent Excitonic Photovoltaic Effect in 2D CsPbBr3/CdS Heterostructures

“…If no other nonradiative decay pathway exists in the recombination process, the thermal activation energy can be regarded as the exciton binding energy. [ 18 ] Here, a B exciton binding energy of 208.5 meV is extracted, which is nearly the same as that of pure CsPbBr 3 (202.1 meV, Figure S13, Supporting Information). Due to the strong quantum confinement in the 2D quantum well, the exciton binding energy is higher than that of bulk CsPbBr 3 (35 meV).…”

Facile NiOx Sol-Gel Synthesis Depending on Chain Length of Various Solvents without Catalyst for Efficient Hole Charge Transfer in Perovskite Solar Cells

“…We found that the normalized PL intensity was the lowest in the “NiO x via B-OH” samples. This suggests that the exciton dissociation (or charge separation) tendency of this material is superior [78,79,80,81]. It was also found that the PCE (%) values of the devices were consistent with this tendency (Table 1).…”