Tailoring the mercaptan ligands for high performance inverted perovskite solar cells with efficiency exceeding 21%

Interface passivation engineering has been recognized as an effective way to simultaneously contribute to the optoelectronic characteristic and stability of perovskite solar cells(PSCs). Herein, a p-conjugated dual-ligand 1,4-phenylmercaptan(PHMT) is explored to rationally tailor the surface of perovskite film.The experimental and theoretical results show that the PHMT presents planar structure and obvious electron delocalization characteristics, which allow it to anchor on the surface of perovskite with a certain orientation, thereby promoting the transport of interface charge. Moreover, the two sulfhydryl groups in PHMT reduce the trap density of the perovskite film by passivating under-coordinated lead ions.Consequently, the PHMT-modified inverted device based on MAPbI_(3)(MA: methylammonium) achieves enhanced efficiency from 18.11%(control) to 21.11%, along with the ambient stability up to 3500 h.After being placed at 85 °C for 500 h or illuminated for 600 h, the modified device remains over 89%or 86% of initial efficiency. This discovery opens a new window for the choice of passivators to improve the performance of PSCs.

Surface modification with ionic liquid for efficient CsPbI2Br perovskite solar cells

The presence of numerous trap states on the perovskite surface severely affects the performance of inorganic CsPbI_(2)Br perovskite solar cells.Surface modification has been proven to be an effective strategy to passivate the surface trap states of CsPbI_(2)Br perovskite.However,most modifiers behave high volatility and insulation,not enough to further develop the CsPbI_(2)Br solar cells.Herein,an ionic liquid of 1-viny-3-propionate ethyl imidazolium chloride([PEVIM]Cl)is applied to modify the CsPbI_(2)Br film surface,yielding a compact film with enhanced crystallinity.The surface trap states of CsPbI_(2)Br film are effectively passivated via the interaction between carbonyl group of[PEVIM]Cl and uncoordinated metal cations of CsPbI_(2)Br perovskite,leading to charge recombination suppression and charge transport enhancement.Consequently,the power conversion efficiency(PCE)of[PEVIM]Cl modified CsPbI_(2)Br device is obviously enhanced from 12.49% to 14.19% with an improved open-circuit voltage of 1.160 V.Moreover,the non-encapsulated device presents excellent thermal stability,still maintaining 91%PCE when heated at 85℃ in nitrogen atmosphere for 360 h.Meanwhile,the non-encapsulated device degrades only 11% PCE after stored at 50% relative humidity for 960 h.This simple and efficient approach provides a promising direction to fabricate high-efficiency and stable inorganic perovskite devices.