NH_(4)PF_(6) assisted buried interface defect passivation for planar perovskite solar cells with efficiency exceeding 21%

The buried interface defects severely affect the further enhancements of efficiency and stability of SnO_(2)-based planar perovskite solar cells(PSCs).To well tackle this problem,we propose a passivation strategy employing NH_(4)PF_6 to modify the buried interface of perovskite layer((FAPbI_(3))_(0.85)(MAPbBr_(3))_(0.15) composition) in planar PSCs.After introducing NH_(4)PF_(6),the oxygen defects on the surface of SnO_(2) film are greatly restricted due to the coordinate interaction between fluorine atoms(F) in PF_(6)^(-)and undercoordinated Sn^(4+).Meanwhile,the hydrogen bonding interaction(N-H…I) between NH_(4)PF_(6) and PbI_(2) can passivate the non-radiative charge recombination sites,significantly optimizing the quality of perovskite film,as well as the charge transfer process at the SnO_(2)/perovskite interface.As a result,the NH_(4)PF_(6)-modified PSC obtains a champion power conversion efficiency(PCE) of 21.11%superior to the reference device(18.46%),and the device with an active area of 1 cm^(2) achieves a PCE as high as17.38%.Furthermore,the unencapsulated NH_(4)PF_(6)-modified PSCs show good humidity stability and retain about80% of the initial PCE after 1080 h aging at the relative humidity(RH) of 35% ± 5%.

Improving performance of Cs_(2)AgBiBr_(6)solar cell through constructing gradient energy level with deep-level hole transport material

The valence band offset between Cs_(2)AgBiBr_(6)and hole transport layer(HTL)is approximately 1.00 e V,which results in high energy loss and is identified as one of the bottle necks of Cs_(2)Ag BiBr_(6)perovskite solar cell(PSC)for achieving high power conversion efficiency(PCE).To tackle this problem,we propose the optimization of the energy level alignment by designing and synthesizing novel deep-level hole transport materials(HTMs).The sole introduction of deep-level HTMs successfully reduces the valence band offset between Cs_(2)Ag Bi Br_(6)and HTL,but induces the increased valence band offset at HTL/Au interface,limiting the PCE improvement.To further solve the problem and improve the PCE,the gradient energy level arrangement is constructed by combining the newly developed deep-level HTM 6,6’-(3-((9,9-dimethyl-9H-fluoren-3-yl)(4-methoxyphenyl)amino)thiophene-2,5-diyl)bis(N-(9,9-dimethyl-9H-fluoren-2-yl)-N,9-bis(4-methoxyphenyl)-9H-carbazol-3-amine)(TF)with 2,2’,7,7’-tetrakis(N,N’-dipmethoxyphenylamine)-9,9-spirobifluorene(Spiro-OMeTAD).Through optimization,an impressive PCE of 3.50%with remarkably high open-circuit voltage(V_(oc))and fill factor(FF)is achieved,qualifying it among the best pristine Cs_(2)AgBiBr_(6)PSCs.