Synergistic passivation of MAPbI_(3) perovskite solar cells by compositional engineering using acetamidinium bromide additives

For the global commercialization of highly efficient and stable perovskite solar cells(PSCs),it is necessary to effectively suppress the formation of various defects acting as nonradiative recombination sources in perovskite light-harvesting materials.Interfacial defects between the charge-selective layer and the perovskite are easily formed in the solution process used to fabricate perovskite films.In addition,owing to the difference in thermal expansion coefficients between the substrate and the perovskite film,internal residual tensile stress inevitably occurs,resulting in increased nonradiative recombination.Herein,a simple compositional engineering scheme for realizing efficient and stable PSCs,which incorporates acetamidinium bromide(AABr)as an additive into the MAPbI_(3) lattice,is proposed.As an additive,AABr has been found to provide synergistic multiple passivation for both internal and interfacial defects.AABr was found to effectively release the tensile strain of the MAPbI_(3) film by forming a structure stabilized by NH-I hydrogen bonds,as evidenced by calculations based on density functional theory(DFT).Furthermore,the incorporated AABr additives created a charge carrier recombination barrier to enhance charge collection capability by reducing interfacial defects.Accordingly,a power conversion efficiency(PCE)of 20.18%was achieved using a planar device employing AABr-incorporated MAPbI_(3).This was substantially higher than the 18.32% PCE of a pristine MAPbI_(3)-based device.Notably,unencapsulated PSCs using AABr-incorporated MAPbI_(3) absorbers exhibited excellent long-term stability,maintaining>95% of initial PCE up to 1200 hours in ambient air.

Influence of a UV-ozone treatment on amorphous SnO_(2) electron selective layers for highly efficient planar MAPbI3 perovskite solar cells

The effect of ultraviolet-ozone(UVO)irradiation on amorphous(am)SnO_(2) and its impact on the photoconversion efficiency of MAPbI3-based perovskite solar cells were investigated in detail.UVO treatment was found to increase the amount of chemisorbed oxygen on the am-SnO_(2) surface,reducing the surface energy and contact angle.Physicochemical changes in the am-SnO_(2) surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite grains.In addition,the Fermi energy of the UVO-treated am-SnO_(2) shifted upwards to achieve an ideal band offset for MAPbI3,which was verified by theoretical calculations based on the density functional theory.We achieved a champion efficiency of 19.01% with a statistical reproducibility of 17.01±1.34% owing to improved perovskite film densification and enhanced charge transport/extraction,which is considerably higher than the 13.78±2.15% of the counterpart.Furthermore,UVO-treated,am-SnO_(2)-based devices showed improved stability and less hysteresis,which is encouraging for the future application of up-scaled perovskite solar cells.

Novel Intense-pulsed-light synthesis of amorphous SnO_(2)electron-selective layers for efficient planar MAPbI_(3)perovskite solar cells

Although perovskite solar cells(PSCs)have achieved a high power conversion efficiency(PCE)within a short period of development,the high-temperature sintering of the constituent electron-selective layers(ESLs)impedes the commercialization.In this report,we demonstrate the effectiveness of an intensepulsed-light(IPL)treatment for the rapid and damage-free sintering of amorphous-SnO_(2)ESLs for use in PSCs.The IPL treatment of amorphous-SnO_(2)substantially reduced the amount of surface hydroxyl groups,modified the surface energy,and enabled the growth of a low-stress perovskite layer with large grain sizes,all of which enhanced the photovoltaic properties and led to the proper alignment of band structures for efficient PSCs.Through comprehensive optimization of the IPL conditions,a PCE of 17.68%was achieved from the MAPb I3 planar PSC based on an amorphous-SnO_(2)IPL treated for a few tens of seconds,which was significantly increased compared with a PCE(7.06%)of nontreated SnO_(2)based counterpart.In addition,the PCE of the IPL-treated SnO_(2)based PSC is comparable to the best PCE(18.16%)of PSCs fabricated with SnO_(2)ESL annealed for three hours at 185℃.Because of its ultrafast sintering time and tendency to not damage SnO_(2)ESLs,the new IPL process is expected to open new opportunities for the commercialization of PSCs.