Organic solar cells based on small molecule donor and polymer acceptor

Small molecule donor/polymer acceptor(SD/PA)-type organic solar cells(OSCs)have attracted widespread attention in recent years due to the continuing power conversion efficiency(PCE)growth,near 10%,and the excellent thermal stability for the practical applications.However,the development of SD/PA-type OSCs lags far behind that of polymer donor/small molecule acceptor(PD/SA)-type OSCs,which are also based on the combination of small molecule and polymer,with the PCEs exceeding 18%.The reasons accounting for this great gap are well worth exploring.In this review,we have analyzed the key factors affecting the photovoltaic performances of SD/PA-type OSCs,systematically summarized the research progress of SD/PA type OSCs in recent years,and put forward our own views on the future development of SD/PA type OSCs.

Enhancing the performances of all-small-molecule ternary organic solar cells via achieving optimized morphology and 3D charge pathways

With the emergence of non-fullerene acceptors(NFAs),the power conversion efficiencies(PCEs)of allsmall-molecule organic solar cells(ASM-OSCs)have been significantly improved.However,due to the strong crystallinities of small molecules,it is much more challenging to obtain the ideal phase separation morphology and efficient charge transport pathways for ASM-OSCs.Here,a high-efficiency ternary ASMOSC has been successfully constructed based on H11/IDIC-4 F system by introduction of IDIC with a similar backbone as IDIC-4F but weak crystallinity.Notably,the addition of IDIC has effectively suppressed large-scale phase aggregation and optimized the morphology of the blend film.More importantly,the molecular orientation has also been significantly adjusted,and a mixed face-on and edge-on orientation has formed,thus establishing a more favorable three-dimensional(3D)charge pathways in the active layer.With these improvements,the enhanced short-circuit current density(JSC)and fill factor(FF)of the ternary system have been achieved.In addition,because of the high lowest unoccupied molecular orbital(LUMO)energy level of IDIC as well as the alloyed structure of the IDIC and IDIC-4F,the promoted open circuit voltage(VOC)of the ternary system has also been realized.