Progress in Physics

Research Progress of Passivation Strategies for Perovskite Films

ZHAO Min, ZHANG Wei-ting, BIAN Hong-tao

2022, 42 (1): 1-16. doi: 10.13725/j.cnki.pip.2022.01.001

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Perovskite solar cells (PSCs) have been developed as a new photovoltaic technology due to their excellent photoelectric conversion efficiency and low cost of manufacturing. The research of PSCs has been boosted especially in the past ten years, and the performance of PSCs has been greatly improved. However, there are more efforts to be done in this field to push the PSCs into the photovoltaic market. The main problem is caused by the limitations of the perovskite film itself during the manufacturing, where the inevitable existence of defects would seriously affect the number and mobility of carriers in the PSCs. All these defects can restrict the improvement of the efficiency and stability of PSCs. In this review article, we briefly introduce the classification of perovskite and their defects. Different strategies for passivation of perovskite films developed in recent years were summarized accordingly. It is expected that the current study would benefit the researchers in the field of perovskite materials and provide valuable insights for them to choose suitable passivating agents.

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Excited-State Dynamics of Large-Sized Thiolate-Protected Au_n (n>100) Nanoclusters

ZHOU Meng

2022, 42 (1): 17-26. doi: 10.13725/j.cnki.pip.2022.01.002

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Gold nanoclusters (size< 2.2 nm) bridge metallic gold nanoparticles and single gold atoms, playing a crucial role in revealing the origin of surface plasmon resonance and metallic bonding. Ligand-protected gold nanoclusters provide a suitable platform to understand metal to non-metal transitions while the excited-state dynamics of gold nanoclusters in the transition regime remain elusive. In this minireview, I summarize the excite-state dynamics of large-sized Aun (n>100) nanoclusters and compare them with those of plasmonic gold nanoparticles. By looking into the electron and vibration dynamics of a series of thiolate-protected gold nanoclusters in the transition regime, the electronic structures of these nanoclusters are further discussed. A deeper understanding of the mechanism of electron relaxation and energy dissipation of large-sized gold nanoclusters will be of great help to connect the optical properties of metal clusters and nanoparticles, which will further promote the design of those functional nanomaterials.

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Excited Carrier Dynamics in Organic Photovoltaic Materials with Non-Fullerene Acceptors

ZHANG Sheng-bing , ZHANG Chun-feng

2022, 42 (1): 27-33. doi: 10.13725/j.cnki.pip.2022.01.003

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The performance of organic photovoltaic (OPV) device has been improved rapidly benefiting from the development of non-fullerene acceptors (NFAs). In these new systems, the mechanism models developed in conventional OPV systems with fullerene acceptors are not fully valid for describing the generation and recombination processes of photo charges. Here, we summarize recent studies on the excited carrier dynamics using ultrafast spectroscopy. In the model systems, an intra-moiety state arising from the molecule interaction mediates the hole transfer channel, allowing charge separation at a small interfacial driving energy. Moreover, the bimolecular recombination plays an important role in voltage loss in OPV blends with NFAs, which can be strongly suppressed by manipulating the alignment of interfacial and local triplet states. The energy landscape of key levels, susceptible to the molecular interaction, is essential for charge generation and recombination, which can be manipulated for future device optimization.

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