A study on the Si1-xGex gradual buffer layer of III-V/Si multi-junction solar cells based on first-principles calculations.

III-V/Si multi-junction solar cells have been widely studied in recent years due to their excellent theoretical efficiency (∼42%). In order to solve the problem of lattice mismatch between Si and III-V compounds of III-V/Si solar cells, different hexagonal Si1-xGex buffer layer models on the surface of hexagonal diamond Si(001) were built, and the structural, electronic and optical properties of the proposed models were calculated based on first principles calculations. The results showed that all models of the designed buffer layer could effectively reduce the lattice mismatch, and the buffer layer hex-Si1-xGex (x = 0, 0.75, and 1) is the ideal model and has achieved the best lattice-matching improvement with high defect formation energy, as well as direct band gap properties and a larger light adsorption coefficient. These theoretical models, with their analyzed properties, could offer a promising pathway toward realizing high efficiency and low cost III-V/Si multi-junction solar cells.

A Functional Biological Molecule Restores the PbI2 Residue-Induced Defects in Two-Step Fabricated Perovskites.

Coating the perovskite layer via a two-step method is an adaptable solution for industries compared to the anti-solvent process. But what about the impact of unreacted PbI2? Usually, it is generated during perovskite conversion in a two-step method and considered beneficial within the grain boundaries, while also being accused of enhancing the interface defects and nonradiative recombination. Several additives are mixed in PbI2 precursors for the purpose of improving the perovskite crystallinity and hindering the Pb2+ defects. Herein, in lieu of adding additives to the PbI2, the effects of the PbI2 residue via the electron transport layer/perovskite interface modification are explored. Consequently, by introducing artemisinin decorated with hydrophobic alkyl units and a ketone group, it reduces the residual PbI2 and improves the perovskites' crystallinity by coordinating with Pb2+. In addition, artemisinin-deposited perovskite enhances both the stability and efficiency of perovskite solar cells by suppressing nonradiative recombination.