Self-assembled interlayer aiming at the stability of NiOx based perovskite solar cells

Inorganic NiO_(x) based inverted structure perovskite solar cells (PSCs) is reported to be more stable than that with the organic hole transport materials.In this work,NiO_(x)/MAPbI_(3) interface chemical reaction induced instability of perovskite is unveiled:Ni^(3+) and I^(-) exhibit redox reactions and deprotonation of MA^(+) happens,which result in interface defects and perovskite lattice deformation.Thus the defective interface accelerates the degradation of perovskite by defect pathways from the bottom interface to the perovskite surface contacting H_(2)O/O_(2).Self-assembled interlayer of NH_(2)^(-)end silane on NiO_(x)separates the reactive NiO_(x)and MAPbI_(3),tunes the interface energy states by–NH_(2) end group.As a result,the PSC based on the silane treated NiO_(x)achieves enhanced PCE of 20.1%with decent stability under environmental and extreme conditions (high temperature,high humidity,light infiltration).Our work highlights the interface chemical problem induced PSC instability and a simple interface modification to achieve the stable PSCs.

Facile Modification on Buried Interface for Highly Efficient and Stable FASn_(0.5)Pb_(0.5)I_(3) Perovskite Solar Cells with NiOx Hole-Transport layers

Formamidinium(FA)-based Sn-Pb perovskite solar cells(FAPb_(0.5)Sn_(0.5)I_(3) PSCs)with ideal bandgap and impressive thermal stability have caught enormous attention recently.However,it still suffers from the challenge of realizing high efficiency due to the surface imperfections of the transport materials and the energy-level mismatch between functional contacts.Herein,it is demonstrated that the modification on buried interface with alkali metal salts is a viable strategy to alleviate these issues.We systematically investigate the role of three alkali metal bromide salts(NaBr,KBr,CsBr)by burying them between the NiOx hole transport layer(HTL)and the perovskite light-absorbing layer,which can effectively passivate interface defects,improve energy-level matching and release the internal residual strain in perovskite layers.The device with CsBr buffer layer exhibits the best power conversion efficiency(PCE)approaching 20%,which is one of the highest efficiencies for FA-based Sn-Pb PSCs employing NiO_(x) HTLs.Impressively,the long-term storage stability of the unencapsulated device is also greatly boosted.Our work provides an efficient strategy to prepare desired FA-based ideal-bandgap Sn-Pb PSCs which could be applied in tandem solar cells.