An inverted planar solar cell with 13% efficiency and a sensitive visible light detector based on orientation regulated 2D perovskites

Abstract

Improving the film quality is of great importance in promoting the power conversion efficiency (PCE) of 2D perovskite-based solar cells (PVSCs), but the solution to this issue is limited. In this work, a strategy of combining the advantages of the ammonium thiocyanate (NH₄SCN) additive and merged annealing (MA) process was applied to fabricate a high quality 2D (PEA)₂(CH₃NH₃)₄Pb₅I₁₆ (PEA = phenylethylammonium, n = 5) film. The optimized planar-structured PVSC with the inverted structure of ITO/PEDOT:PSS/(PEA)₂(CH₃NH₃)₄Pb₅I₁₆/PC₆₁BM/BCP/Ag presents a high fill factor of 0.77 and the best PCE of 13.01%. This FF is the highest value for low-n (n < 10) 2D PVSCs. The performance elevation can be attributed to the NH₄SCN assisted highly vertical orientation together with the MA process induced crystallinity improvement and effective defect passivation, which resulted in efficient charge transport and reduced nonradiative recombination. The unsealed device retains 50% of its original PCE after 30 day storage in air with a humidity of 25 ± 5%. The high-quality perovskite thin-film with low trap density exhibits suppressed dark current density. The MA-based device presents the highest shot noise limited specific detectivity over 10¹² Jones in the visible region. This work provides an effective approach toward high-performance and stable PVSCs and photodetectors for future commercialization.