Research On Excellent Organic-inorganic Hybrid Perovskite Solar Cells

The excellent performance of orgmental halide perovskites based optoelectronic devices are originated from their splendid properties such as high charge carrier mobility,extremely low trap density,long electron-hole diffusion length,and small exciton-binding energy.Solar cells with hybrid organic-inorganic perovskite materials as absorber have experienced an explosive development.Their PCEs have rapidly rose from the initial 3.8%in 2009 to a certified 22.1%in 2016.Organic-inorganic hybrid perovskite material has become the most attractive photovoltaic material.Although the perovskite solar cell has experienced a very fast development,at present,the unstanding for perovskite solar cell beyond the PCEs are not enough,such as perovskite film-forming mechanism,working mechanism of device,and need further investigation.The main part of this focuses on mechanism of perovskite film formation with additives and its influence on perovskite solar cells performance.The work includes the following several aspects:?.The study on the impact of Cl-and Br-additive on the efficiency of perovskite solar cells three different perovskite film,CH3NH3PbI3,CH3NH3PbI(3-x)Clx and CH3NH3PbI(3-x)Brx,have been fabricated and optimized as the absorber layers for perovskite solar cells.We find:1.The CH3NH3PbI3 solar cells exhibited with power conversion efficiency(PCE)of 15.86%,with short-circuit current density(Jsc)=21.90 mA/cm2,open-circuit voltage(Voc)= 1.02 V,and fill factor(FF)= 71%.2.The mesoporous structure CH3NH3PbI(3-x)Clx solar cells exhibited with PCE=16.43%,Jsc=21.91mA/cm2,Voc=1.00V,and FF=75%.3.CH3NH3PbI(3-x)Brx perovskite solar cells does not only show high PCEs(18.93%)with Jsc= 23.37 mA/cm2,Voc= 1.08V,FF = 75%,but also better thermal stability than CH3NH3PbI3.Further studies found that photoluminescence of CH3NH3PbI(3-x)Brx,films were blue shifted with increasing of the PbBr2 concentration,and the CH3NH3PbI(3-x)Br,solar cells exhibited with Js,= 23.37 mA/cm2,VOc=1.08 V,FF = 75%,and PCE=18.93%,respectively.The results demonstrate that adding a small amount of PbBr2 in the perovskite precursor can significantly increase the grain size and crystalline quality of perovskite thin films and improve photovoltaic performances.?.The effect of transparent conductive oxide(TCO),like ITO,FTO and AZO,on the performance of compact-layer free perovskite solar cells has been investigated.The results show that the perovskite film formation,charge transfer and charge recombination are affected by different TCO layers.All common TCOs,show some beneficial and detrimental characters for solar cell application.Finally,the compact-layer free perovskite solar cells based on them show similar performance.?.The high efficiency of planar-type perovskite solar cells severely require the absorber layers with good crystallization and high surface coverage.However,the two key factors are still main challenges in perovskite filmformation to date.In this part the effective additive and mesoporous structure on the performance of FAPbI3 solar cell has been investgated.1.The 1-Chloronaphthalene(1-CN)is used as solvent-additive into the precursor HC(NH2)2PbI3(FAPbI3)solution to control the crystallization and surface coverage of the FAPbI3 films.The 1-CN chlorinated monodentate ligand is likely to temporarily chelate with Pb2+ during crystal growth,facilitating homogenous nucleation to form relative high quality FAPbl3films.Meanwhile,the 1-CN additive with high boiling point delays the growth rate of FAPbI3 film to facilitate the formation of homogenous and continuous FAPbI3 films with fewer pin-holes.As a result,with the addition of 1-CN solvent-additive,the efficiency of FAPbI3 planar-type solar cells is enhanced to 16.53%.2.The research on preparation of mesoporous structure FAPbI3 perovskite solar cells found perovskite material can be fully populated titanium dioxide pore,increasing contact area between perovskite and titanium dioxide,which can produce a higher Voc,FF,PCE(19.04%)than the planar-type structure,and descrease the hysteresis effect greatly.3.An inverted planar FAPbI3 perovskite solar cell with structure of FTO/PEDOT:PSS/FAPbI3/PCBM/Ag has been fabricated and studied.A highest PCE of 8.66%without J-V hysteresis has been obtained with Jsc=14.48 mA/cm2,Voc=0.88 eV,FF=68%,respectively.The results showed that mesoporous structured FAPbI3 perovskite solar cells can deliver the best photovoltaic performances.Mesoporous structure and inverted structure can reduce the hysteresis of perovskite solar cells.?.Planar-structured FA0.83MA0.17Cs0.05PbI(3-x)Brx perovskite solar cells were prepared via a single-step deposition process with adding Pb(SCN)2.As a result,grain sizes of the deposited FA0.83MA0.17Cs0.05PbI(3-x)Brx became larger with the Pb(SCN)2 concentration increased from 1mol%to 10 mol%.The influence of the Pb(SCN)2 cotent on the morphology,photovoltaic performances and stability of perovskite solar cell was investigated.As the content of Pb(SCN)2 is 5 mol%,the FA0.83MA0.17Cs0.05PbI(3-x)Brx solar cells exhibited open circuit voltage of 1.18 eV with PCE of 18.51%.The results demonstrate that adding a small amount of Pb(SCN)2 in the perovskite precursor can significantly improved the stability of perovskite solar cells as well as photovoltaic performance.