Morphology Optimization In High Performance All-Polymer Solar Cells

Polymer-polymer organic solar cells(all-PSCs)have attracted considerable attentions in recent years due to their excellent flexibility and mechanical stability.In this thesis,through systematically morphological optimization,including thermal annealing treatment and "solid additive" strategy,we successfully improved the morphology of all-polymer bulk hetero-junction blends.Furthermore,the stability of all-polymer devices was also investigated under different conditions.Firstly,we report all-PSCs employing our previously reported polymers PBPT-8 and PBPT-12 as donor and n-type polymer P(NDI20D～T2)as acceptor.The performance optimization of these all-PSCs by thermal annealing was investigated and discussed.Decent power conversion efficiency-3%was demonstrated for both all-PSCs without any treatment.Thermal annealing of the active blend layer can contribute greatly to the device morphology.Best PCEs 4.12%and 4.25%have been achieved for PBPT-8:N2200 and PBPT-12:N2200 systems with the same optimal annealing temperature of 160℃.Secondly,we developed an efficient strategy of "solid addictive" for all-PSCs.In this contribution,we disclosed the design and fabrication of all-PSCs by incorporating small amount of small molecule acceptor(ITIC)to further improve the maximum PCE from 6%to over 7%.More importantly,this "solid additive" strategy exhibits certain universal capability,which has been examined in all-PSCs by adopting classical P3HT and efficient low D-A copolymer PTB7.Through in depth device and morphology characterization,we found the addition of third component can tune the optical and morphological properties more comprehensively.Furthermore,the charge carrier generation and charge carrier mobility can be simultaneously improved.Finally,the stability of all-polymer devices was also investigated compared to that of polymer/fullerene system.The all-PSCs exhibit long-term stability either under dark environment storage or continuous thermal annealing.