Bulk heterojunction perovskite solar cells incorporated with solution-processed TiOx nanoparticles as the electron acceptors

In the past ten years,perovskite solar cells were rapidly developed,but the intrinsic unbalanced charge carrier diffusion lengths within perovskite materials were not fully addressed by either a planar heterojunction or meso-superstructured perovskite solar cells.In this study,we report bulk heterojunction perovskite solar cells,where perovskite materials CH3NH3PbI3 is blended with solution-processed n-type TiOx nanoparticles as the photoactive layer.Studies indicate that one-step solution-processed CH3NH3PbI3:TiOx bulk-heterojunction thin film possesses enhanced and balanced charge carrier mobilities,superior film morphology with enlarged crystal sizes,and suppressed trapinduced charge recombination.Thus,bulk heterojunction perovskite solar cells by CH3NH3PbI3 mixed with 5 wt% of TiOx,which is processed by one-step method rather than typical two-step method,show a short-circuit current density of 20.93 mA/cm2,an open-circuit voltage of 0.90 V,a fill factor of 80% and with a corresponding power conversion efficiency of 14.91%,which is more than 30% enhancement as compared with that of perovskite solar cells with a planar heterojunction device structure.Moreover,bulk heterojunction perovskite solar cells possess enhanced device stability.All these results demonstrate that perovskite solar cells with a bulk heterojunction device structure are one of apparent approaches to boost device performance.

Ternary solvent-processed efficient organic solar cells based on a new A-DA'D-A acceptor derivative employing the 3^(rd)-position branching side chains on pyrroles

Recent advances in non-fullerene acceptors(NFAs),typically Y6,have driven power conversion efficiency(PCE) of single-junction orga nic solar cells(OSCs) over 16%.Mea nwhile,it becomes essential to know how to adopt simple strategies to further improve device performance.In this work,a new A-DA'D-A acceptor derivative,Y19-N3 employing 3-ethylheptyl branched at the 3^(rd)-position instead of 2-ethylhexyl on the pyrroles of Y19 is reported.The selection of an appropriate solvent in casting device is implemented to maximize the photovoltaic performance.PBDB-T:Y19-N3-based OSCs treated with a ternary solvent of CF/CB(1:3,v/v) and 0.8% DIO exhibit the optimal PCE of 13.77% here,with the significantly improved V_(oc)(0.78 V) and FF(0.72) as well as the high J_(sc)(24.46 mA/cm^(2)).Further characterizations indicate that this ternary solvent-treated PBDB-T/Y19-N3 film exhibits the more appropriate morphological features with the highly efficient charge generation and collection as well as the more balanced electron and hole mobilities.This work combines molecular design and device engineering to improve the photovoltaic properties,which is important to the development of OSCs.