Recent Progress of Layered Perovskite Solar Cells Incorporating Aromatic Spacers

Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells(PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.

Major strategies for improving the performance of perovskite solar cells

Metal halide perovskite solar cell(PSC)has successfully distinguished itself in optoelectronic field by virtue of the sharp rise in power conversion efficiency over the past decade.The remarkable efficiency breakthrough at such a fast speed can be mainly attributed to the comprehensive study on film deposition techniques,especially the effective management of surface and interfacial defects in recent works.Herein,we summarized the current trends in performance enhancement for PSCs,with a focus on the generally applicable strategies in high-performance works,involving deposition methods,compositional engineering,additive engineering,crystallization manipulation,charge transport material selection,interfacial passivation,optical coupling effect and constructing tandem solar cells.Promising directions and perspectives are also provided.

Novel Hybrid Ligands for Passivating Pb S Colloidal Quantum Dots to Enhance the Performance of Solar Cells

We developed novel hybrid ligands to passivate Pb S colloidal quantum dots(CQDs),and two kinds of solar cells based on as-synthesized CQDs were fabricated to verify the passivation effects of the ligands.It was found that the ligands strongly affected the optical and electrical properties of CQDs,and the performances of solar cells were enhanced strongly.The optimized hybrid ligands,oleic amine/octyl-phosphine acid/Cd Cl2improved power conversion efficiency(PCE)to much higher of 3.72%for Schottky diode cell and 5.04%for p–n junction cell.These results may be beneficial to design passivation strategy for low-cost and high-performance CQDs solar cells.

Frequency steering of spaceborne clocks based on XPNAV-1 observations

Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by XPNAV-1 satellite, we study the possibility of correcting the frequency deviation of spaceborne atomic clocks using pulsar timing. According to the observational data in X-ray band and the timing model parameters from radio observations, the pre-fit timing residuals with a level of 67.66 μs are obtained. By fitting the slope of the timing residuals affected by the faked frequency-biased reference clock, we estimated successfully the relative frequency deviation of the reference clock. For a satellite clock with frequency deviation of the order about 10^(-12), a calibration accuracy with relative error of about 2% can be obtained from the Crab pulsar’s data for one year.The stability of the time scale based on Crab pulsar is about 10^(-12) for an interval of one year.