Mixed 2D-Dion–Jacobson/3D Sn-Pb alloyed perovskites for efficient photovoltaic solar devices

Tin-lead(Sn-Pb)alloyed perovskites with tunable bandgaps hold great potential for constructing highly efficient single-junction and tandem photovoltaic devices.However,the efficiency and stability of Sn-Pb perovskite solar cells(PSCs)are greatly hampered by severe nonradiative recombination due to the easy oxidation of Sn(II).In this work,we report the construction of mixed dimensional two-dimensional(2D)Dion–Jacobson(DJ)and three-dimensional(3D)perovskites to improve the efficiency and stability of Sn-Pb alloyed PSCs.Introducing a small amount of 1,4-butanediammonium diiodide as spacer cations of DJ perovskites into precursor,the prepared mixed dimensional Sn-Pb alloyed perovskites exhibit reduced trap-state density due to the passivation of 2D DJ perovskites.As a result,nonradiative charge recombination is greatly suppressed.The prepared Sn-Pb alloyed PSCs based on 2D-DJ/3D heterojunction deliver a power conversion efficiency of 19.02%with an impressive fill factor of 80%.As well,improved device stability is realized due to the presence of DJ perovskites which serves as a protection barrier against oxidation and water invasion.

Advanced non-precious electrocatalyst of the mixed valence CoO_x nanocrystals supported on N-doped carbon nanocages for oxygen reduction

Taking advantage of the nitrogen(N)-participation and large surface area of N-doped carbon nanocages(NCNCs),the Co Ox nanocrystals are conveniently immobilized onto the NCNCs with high dispersion.The Co Ox/NCNCs hybrid exists in the mixed valence with predominant Co O over Co3O4 and demonstrates superb oxygen reduction reaction activity and stability remaining^94%current density even after operation over 100 h.These results suggest a promising strategy to develop advanced electrocatalysts with the novel NCNCs or even beyond.