A solution-processed nanoscale COF-like material towards optoelectronic applications

Two-dimensional(2 D)covalent organic frameworks(COFs)with periodic functionalπ-electron systems are an emerging class of optoelectronic materials.However,almost all conjugated COFs so far are insoluble and hard to process,which hampers severely their optoelectronic applications.Here,a solution-processable,nanoscale and sp2 carbon-conjugated COF-like material,PDPP-C20 was successfully designed and synthesized.The solution-processed PDPP-C20 films exhibit high crystallinity and excellent charge transport properties along out-of-plane directions,combined with the highest occupied molecular orbital(HOMO)/lowest unoccupied molecular orbital(LUMO)levels of-5.36/-3.75 e V,making PDPP-C20 suitable for electronic device applications.An efficiency as high as 21.92%has been demonstrated when it was used as a functional interfacial layer in perovskite solar cells,coupled with dramatically improved stability in comparison with the control device due to the superior hydrophobicity of PDPP-C20 layer as well as its passivation effect on perovskite surface.Furthermore,the soluble PDPP-C20 could also be used as donor in bulk-heterojunction organic solar cells and an initial efficiency of 2.46%has been achieved.These results indicate that this new class of soluble and nanoscale COF-like materials should offer a new arena of functional materials for optoelectronic devices.