Study On Fabrication And Photovoltaic Property Of CH₃NH₃Pb(I_1-xBr_x)₃ Planar Heterojunction Perovskite Solar Cell

Since the 20th century,the world faces serious energy and environmental problems.However,the growing population of the world makes these problems more serious.So it is imperative to make effective use of renewable energy as soon as possible.Organic-inorganic hybrid perovskite materials with good optical and electrical properties,is considered to be the best solution to solve the solar energy utilization at present.Perovskite solar cell have developed rapidly in a short time.The power conversion efficiency?PCE?has grown from 3.8%in2009 to 23.3%today,which had achieved by other types of solar cells through decades of efforts.Moreover,the simple and high-temperature-treatment free preparation technology make perovskite solar cell have extremely wide prospect for commercialized application.Solvent engineering is an effective way to improve the performance of perovskite solar cell.In this paper,a novel solvent annealing method is applied to fabricate the CH₃NH₃Pb(I_1-xBr_x)₃ perovskite solar cell on the basis of CH₃NH₃Pb I₃ film.It effectively improve the open circuit voltage and power conversion efficiency compared with the parental solar cell.The novel process is simple and low cost.It offers a new way to fabricate high performance CH₃NH₃Pb(I_1-xBr_x)₃-based solar cells.This paper is divided into two parts:?1?The preparation method of CH₃NH₃Pb(I_1-xBr_x)₃ films by HBr/DMSO mixed solvent annealing was studied.HBr/DMSO mixed vapor was used as the solvent annealing atmosphere to transform CH₃NH₃PbI₃ film into CH₃NH₃Pb(I_1-xBr_x)₃ film.The obtained CH₃NH₃Pb(I_1-xBr_x)₃ under this mixed vapor have high coverage and uniformly distributed bromine.In this paper,many tests were done to study the influence of HBr/DMSO system on the composition and interface of perovskite films.The reaction mechanism between HBr/DMSO system and CH₃NH₃PbI₃ film was revealed.This work provided an effective and environmentally friendly bromination method for preparation of high quality CH₃NH₃Pb(I_1-xBr_x)₃ film.By this method,the maximum PCE of15.7%was achieved for the perovskite solar cell with an inverted structure(ITO/PEDOT:PSS/CH₃NH₃Pb(I_1-xBr_x)₃/PC₆₁BM/Bphen/Ag).?2?The repairing effect of methylamine vapor annealing on the surface defects of perovskite films was studied.Due to HBr/DMSO acidity,the abovementioned bromination reaction inevitably damage to the surface and crystal structure of perovskite film,and thus led the increase in surface roughness.In order to repair the damaged perovskite film and decrease the film roughness the methylamine vapor annealing method was proposed in this work.A variety of characterization methods were employed to study the repairing effect of methylamine vapor.It is found that methylamine vapor treatment can reconstructed the microstructure of MAPb(I_1-xBr_x)₃ perovskite film for defect-healingbytheformationandspreadingofanintermediate CH₃NH₃Pb I₃·xCH₃NH₂ liquid phase,and thus improve crystal quality and make the perovskite surface become more smooth.In a word,HBr/DMSO mix vapor treatment combined with methylamine vapor annealing resulted in a significant improvement in performance of MAPb(I_1-xBr_x)₃-based perovskite solar cell,achieved the highest efficiency of 17.23%.This is a novel and efficient way to fabricate bromine doped perovskite solar cell.