Device Engineering Of Organic Solar Cells

Organic solar cells(OSCs)have been considered as one of the most promising technologies for converting light to energy because of their remarkable advantages,such as light weight,flexibility,solution processing,large-area production and low-cost.In the past two decades,power conversion efficiencies(PCEs)of solution-processed single junction and tandem OSCs have exceeded over 15%and 17%respectively,due to the significant efforts in materials development,morphology control,interface engineering and device architecture design.To successfully realize the practical use of OSCs,it is crucial to pay much more efforts in improving device stability and developing upscaling techniques.This thesis focuses on the device engineering and provides new strategies to improve the performance of OSCs,the main achievements are descried below:1.We successfully improved the photon-to-electron response of PTB7:PC71BM blend based OSCs by incorporating a low-band gap polymer PDTP-DFBT and utilizing modified ZnO as electron transport layer.The absorption edge of the ternary blend active layer was extended from 800 to 900 nm.A charge transfer mechanism between PTB7 and PDTP-DFBT was confirmed from photoluminescence spectra.π-π stacking and face-on orientation of the polymer blend was enhanced through the addition of PDTP-DFBT.Finally,we achieved an efficient ternary OSC with PCE of 9.06%.2.We successfully achieved an efficient and stable ternary OSCs by incorporating a small-molecule dye BTPE-Rn into PTB7-Th:PC71BM blend films processed without 1,8-diiodooctane(DIO).An investigation of the optical,electronic,and morphological properties of the ternary blends indicated that the BTPE-Rn not only promoted the photon utilization of blends through the energy-transfer process but also improved the electron mobility of the blends owing to the fullerene-rich nanophase optimization.In addition,this ternary strategy of utilizing a small-molecule dye to replace the photounstable DIO additive enhanced the light stability of the OSCs.3.We successfully improved the device performace of the PBDB-T:ITIC-based inverted non-fullerene OSCs by modifying the ZnO with three small molecules aminopropanoic acid(C3),4-Aminobenzoic acid(ABA)and 4-methoxybenzoic acid(MoBA).The ultraviolet photoelectron spectroscopy results revealed that the SAMs could lower the surface work function of ZnO,allowing for better electron extraction.The analysis results of J-V characteristics under different light illumination intensities suggested more efficient charge dissociation and weaker trap-assisted bimolecular recombination in the devices with SAMs modification.Finally,we achieved an efficient non-fullerene OSC with PCE of 10.90%based on C3 modified ZnO.