Application Of Two-dimensional Antimony Quantum Sheets In Highly Efficient Organic Solar Cells

Organic solar cells（OSCs）consisting of organic materials as light absorbers are a promising next-generation photovoltaic technologies to harvest clean and renewable solar energy.Organic solar cells have appeared as a prospective design for next-generation photovoltaic technologies owing to their cost-efficient fabrication processes and excellent photovoltaic performance.The emergence of new D/A copolymer donor and non-fullerene acceptor quickly pushes the PCE to 18%in single-junction OSCs.Apart from the efforts in synthesis of low-bandgap polymer donors and nonfullerene acceptors,the introduction of novel optoelectronic materials is believed to play a critical role in further improving the overall photovoltaic performance of OSCs,and has become a hot spot.In recent years,two-dimensional materials have attracted a great deal of attention in organic photovoltaics because of their adjustable photoelectric properties and band gap,higher carrier mobility,lower light scattering loss,and semiconductor process compatibility.Till now,two-dimensional materials have been successfully introduced into the electrodes,interface layers and light absorbers of OSCs.However,the current two-dimensional materials have the problems of band gap incompatibility and poor stability.Therefore,it is necessary to develop novel two-dimensional material and then introduce it into organic solar cells to enhance device performance and stability.In this dissertation,we introduced a novel two-dimensional material:antimony quantum sheets（QSs）,which have shown high stability,a low bandgap,high electrical conductivity and carrier mobility.QSs is applied as a class of interface materials and a additive into light absorber to systematically investigate the effect of QSs on the photovoltaic.Firstly,the thickness of PTB7-Th:PC₇₁BM light absorber,PTB7-T:ITIC light absorber,Cu SCN hole extraction layer（HEL）and Zn O electron extraction layer（EEL）were optimized to obtain a higher PCE in OSCs.Then,QSs interlayer was inserted into an OSCs,which using Cu SCN as the hole extraction layer and PTB7-Th:PC₇₁BM as the light absorber,and the thickness of the QSs interlayer was systematically optimized.The results has proved that the insertion of QSs interlayer efficiently helps to improve the interface contact between the hole extraction layer and the light absorber,promote more efficient exciton dissociation in the device.The application of Cu SCN/QSs hole extraction layer enables to depress the exciton quenching at the interface between Cu SCN and PTB7-Th:PC₇₁BM light absorber,reduce the charge recombination loss,improve the electrons extraction efficiency in OSCs,resulting in significant improvement of photovoltaic performance.Compared with the reference device with pristine Cu SCN as the hole extraction layer,impressive improvements of short-circuit current density(J_sc)and power conversion efficiency（PCE）are observed in cells using Cu SCN/QSs as HEL,the J_scincreased from15.2 m A cm^-2 to 17.1 m A cm^-2,and the power conversion efficiency（PCE）increased from 7.86%to 8.80%.At the same time,the universality of Cu SCN/QSs HEL was observed in nonfullerene PBDBT-2F:IT-4F and PTB7-Th:ITIC blend system-based cells.Finally,QSs was selected as additive into the light absorber,and the additive QSs was introduced into OSCs based on PTB7:PC₇₁BM,the effect of QSs on active blend films and photovoltaic characteristics was systematically studied.The concentration of the QSs interlayer was carefully optimized.This study proves that the introduction of QSs interlayer efficiently helps to enhance the light absorption of light absorber,promote the exciton generation and separation,reduce charge recombination loss,improve the electrons extraction efficiency,resulting in significant improvement of photovoltaic performance.Compared with the reference device,after using QSs additive,the J_scincreased from 15.7 m A cm^-2 to 18.3 m A cm^-2,the FF increased from0.66 to 0.72,and the power conversion efficiency（PCE）increased from 7.76%to9.75%.Meanwhile,the universality of QSs additive was observed in and P3HT:PC₆₁BM nonfullerene PTB7-Th:ITIC blend system-based cells.