苯基硫脲调控CsPbIBr_(2)钙钛矿结晶及其光电性能

Tailoring of CsPbIBr_(2) perovskite crystallization via phenylthiourea for stable and efficiency perovskite solar cells

无机CsPbIBr_(2)钙钛矿具有较高的稳定性和适合的带隙,因此是一种较有应用前景的太阳能电池光吸收材料.高质量的CsPbIBr_(2)钙钛矿膜是组装高性能CsPbIBr_(2)钙钛矿太阳能电池的关键.本文通过在CsPbIBr_(2)前驱体中加入苯基硫脲(PTU)调控前驱体反应结晶过程,制备高质量的CsPbIBr_(2)钙钛矿膜.由于PTU与CsPbIBr_(2)前驱体组分间存在较强的相互作用,因此加入PTU导致在前驱体中形成PTU·Pb···Br(I)中间相.PTU·Pb···Br(I)中间相能够降低CsPbIBr_(2)钙钛矿成核速率,调控结晶生长过程,从而制备了晶粒尺寸大、结晶度高、缺陷少的高质量CsPbIBr_(2)钙钛矿膜.同时,前驱体热处理结晶过程中,PTU分解使S2–嵌入CsPbIBr_(2)钙钛矿晶格,显著提高了CsPbIBr_(2)钙钛矿的稳定性.本文所组装的碳基钙钛矿太阳能电池光电转换效率达到10.09%.未密封电池在空气环境中贮存35 d,效率仍能保持初始值的82%,表明具有较高的稳定性.

Inorganic CsPbIBr_(2)perovskite has been considered as a promising light-absorbing material for solar cells due to its high stability and suitable bandgap.Although the remarkable improvement of CsPbIBr_(2)PSC has been achieved,the efficiency of this cell is still lower than those of other analogues and far below its theoretical limit.This is mainly due to the serious charge recombination in the as-fabricated CsPbIBr_(2)cells derived from the poor-quality CsPbIBr_(2)perovskite film with a large quantity of defects and numerous grain boundaries.Therefore,fabricating high-quality CsPbIBr_(2)perovskite film is a key factor for the further efficiency improvement of CsPbIBr_(2)PSCs.Herein,phenylthiourea(PTU)additive is introduced into the CsPbIBr_(2)precursor to tailor the crystallization of CsPbIBr_(2)perovskite for fabricating high-quality CsPbIBr_(2)perovskite.The C=S group of PTU can coordinate with PbBr_(2)in the precursor owing to the lone-pair electrons on S and the empty orbits of Pb2+.The strong interaction between PTU and the CsPbIBr_(2)precursor components can form PTU·Pb···Br(I)intermediate phase in the precursor upon PTU introduction.The PTU·Pb···Br(I)intermediate phase can reduce the nucleation rate of perovskite and modulate the perovskite crystal growth because the extra energy is required to break the strong coordination bond in the intermediate phase,resulting in a low crystallization rate of CsPbIBr_(2)perovskite.Such a retardation of perovskite crystallization is conducive to the formation of highcrystallinity perovskite film with smooth surface,large crystal grains,high crystallization,and low density of defect.Meanwhile,the decomposition of PTU during thermal annealing makes the S2–inserted into interstitial of CsPbIBr_(2)crystal lattice,which greatly enhance the stability of CsPbIBr_(2)perovskite.The carbon-based PSCs with a normal n-i-p structure of FTO/compact-TiO2 layer/meso-TiO2 layer/perovskite film/carbon layer are fabricated,and their photovoltaic performances are measured under a simulated AM1.5 illumination(100 mW·cm–2).The PSC based on PTU-CsPbIBr_(2)perovskite delivers a high power conversion efficiency of 10.09%,which is much higher than that of the control device.This great improvement of photovoltaic performance can be attributed to the largely promoted perovskite quality,which enhances the charge collection and suppresses the charge recombination in the device.In addition,the unencapsulated device preserves 82%of the initial efficiency after being stored under ambient condition for 35 days,suggesting excellent stability.Therefore,this work provides an effective complementary strategy for effectively improving the performance of inorganic PSCs.