N-Type Doping Of Electron Transport Layer And The Application In Photovoltaic Devices

Electron transporting layer is a key component of photovoltaic devices which significantly influence the performance of the devices.The typically used electron transporting material of fullerene(PC₆₁BM)have low charge carrier mobility and carrier concentration.N-type doping is an efficient strategy to tune these properties.However,efficient low-temperature n-type dopants are still lacking.In this thesis,we present two n-type dopants to dope the PC₆₁BM and apply in perovskite and organic solar cells.Firstly,we report that a pyridine derivative 2,6-Py can be used to dope PC₆₁BM by mixing their solutions.Conductivity of PC₆₁BM increased by two orders of magnitude after 2,6-Py doping,and the electron mobility also increased.In addition,2,6-Py as a Lewis base can passivate surface defects of the perovskite film and reduce carrier recombination loss.When the doped PC₆₁BM was used as the electron transporting layer in inverted planar perovskite solar cells,device efficiency can be increased from 15.53 to 18.28%.Secondly,another stronger n-type dopant 1,3,5-trimethylhexahydro-1,3,5-triazine（TMHT）was reported.The TMHT doping can increase the conductivity of PC₆₁BM increased by three orders of magnitude.The work function moved from 4.8 to 4.4 e V.Subsequently,the doped PC₆₁BM was used as the electron transport layer in the nonfulleren organic solar cells.The doping can result in the elimination of severe"S"type in the J-V curve of the undoped device due to the enhanced conductivity and shifted Fermi energy levels.Using TMHT-doped PC₆₁BM as the electron transporting layer,non-fullerene organic solar cell shows an efficiency up to 11.41%.