Cesium lead halide (CsPbX) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce, Sm, Eu, Tb, Dy, Er, and Yb) into the lattices of CsPbCl perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

Quantum cutting can realize the emission of multiple near-infrared photons for each ultraviolet/visible photon absorbed, and has potential to significantly improve the photoelectric conversion efficiency (PCE) of solar cells. However, due to the lack of an ideal downconversion material, it has merely served as a principle in the laboratory until now. Here, the fabrication of a novel type of quantum cutting material, CsPbCl Br :Yb , Ce nanocrystals is presented. Benefiting from the larger absorption cross-section, weaker electron-phonon coupling, and higher inner luminescent quantum yield (146%), the doped perovskite nanocrystals are successfully explored as a downconverter of commercial silicon solar cells (SSCs). Noticeably, the PCE of the SSCs is improved from 18.1% to 21.5%, with a relative enhancement of 18.8%. This work exhibits a cheap, convenient, and effective way to enhance the PCE of SSCs, which may be commercially popularized in the future.

long carrier diffusion lengths, adjustable bandgaps, and low-cost fabrication. [1][2][3] Until now, the certified power conversion efficiency (PCE) has reached 25.5%, [4] making the PSC a promising candidate for the next-generation thin-film solar cells. [3,5] However, the presently obtained record PCE is still far from Shockley-Queisser limit efficiency. [6] In addition, the currently achieved stability is much lower below the standard of commercial application. It is well known that poor perovskite film quality is one of the main reasons for efficiency and stability losses. Consequently, it is highly expected to minimize the trap-assisted nonradiative recombination losses via improving perovskite film quality.The traditional solution method with fast crystallization and high-temperature annealing process would inevitably lead to a variety of defects in perovskite bulk and at the surfaces and grain boundaries (GBs). [7][8][9] Most defects in the bulk of perovskite films are shallow-level defects, while most defects at the surface and GBs of perovskite films are deep-level defects, which is detrimental to device performance through capturing carriers. [6,10,11] Moreover, these defects would provide pathways for ion migration, which results in efficiency and stability losses. [6,12,13] In addition, water and oxygen would preferentially attack the surface and GBs of perovskiteThe nonradiative recombination losses resulting from the trap states at the surface and grain boundaries directly hinder the further enhancement of power conversion efficiency (PCE) and stability of perovskite solar cells. Consequently, it is highly desirable to suppress nonradiative recombination through modulating perovskite crystallization and passivating the defects of perovskite films. Here, a simple and effective multifunctional additive engineering strategy is reported where 11 Maleimidoundecanoic acid (11MA) units with carbonyls (carboxyl and amide) and long hydrophobic alkyl chain are incorporated into a perovskite precursor solution. It is revealed that improved crystallinity, reduced trap state density, and inhibited ion migration are achieved, which is ascribed to the strong coordination interaction between the carbonyl groups at both sides of 11MA molecules and Pb 2+ . As a result, improved efficiency and stability are achieved simultaneously after introducing 11MA additive. The device with 11MA additive delivers a champion PCE of 23.34% with negligible hysteresis, which is significantly higher than the 18.24% of the control device. The modified device maintains around 91% of its initial PCE after aging under ambient conditions for 3000 h. This work provides a guide for developing multifunctional additive molecules for the purpose of simultaneous improvement of efficiency and stability.