Bulk Heterojunction Solar Cells Based On Porphyrin Small Molecular Interlayers And Green Solvent

Polymer solar cells(PSCs)are very promising in renewable energy due to their advantages of high flexibility,light-weight and potentially low cost.In order to improve device performance of PSCs,electrode transport layers(ETLs)are widely employed because they can reduce contact resistance and inhibit interfacial charge recombination.A water/alcohol soluble conjugated porphyrin small molecule FNEZnP-OE is designed and synthesized as a cathode interfacial material(CIM),and the PTB7:PC71BM and PTB7-Th:PC71BM based devices with FNEZnP-OE exhibit power conversion efficiencies(PCEs)of 8.52% and 9.16%,respectively,which are increased by 47% and 41% compared to the devices with no ETL(5.78% and 6.50%),respectively.Most significantly,these PCEs are increased by 13.6% and 8%,respectively,than those with widely used polymer ETLs PFN.By doping Zn O with porphyrin small molecules(FNEZnP-OE and FNEZn P-T),the inverted polymer solar cells(i-PSC)with PTB7:PC71BM as the active materials exhibit enhanced device performance.While the power conversion efficiency(PCE)of the PSCs with pure ZnO ETL is 7.52%,that of the devices with FNEZnP-T-doped Zn O ETL shows a slightly improved PCE of 8.09%,and that of the PSCs with FNEZnP-OE-doped ZnO ETL is further enhanced up to 9.24% with an over 20% improvement compared to that with pure ZnO ETL.More importantly,the PCE is still higher than 8% even when the thickness of FNEZnP-OE-doped ZnO ETL is up to 110 nm,which are important criteria for eventually making organic photovoltaic modules with roll-to-roll coat processing.Though much progress has been achieved for bulk-heterojunction(BHJ)organic solar cells(OSCs),the best performance devices are processed with halogenated solvents.And the halogenated solvents should be replaced for the practical applications of OSCs due to the toxicity of halogenated solvents to human being and environment.In this study,OSCs based on a porphyrin small molecule are fabricated with toluene and o-xylene,which show high PCEs up to 5.46% and 5.85%,respectively.The both PCEs are the highest for small molecule-based OSCs processed with non-halogenated solvents,demonstrating that porphyrin small molecules are very promising for solar cell commercial applications.