Integrating a third component into the binary system is considered to be one of the most effective strategies to further enhance the power conversion efficiency (PCE) in organic solar cells (OSCs). Here, a novel perylene diimide (PDI) derivative featuring 3D structure, TPA-4PDI, with tetraphenyladamantane central core is developed as a guest electron acceptor to be incorporated into the PM6:Y6 binary system. The champion PCE of ternary OSC is recorded to be 18.29% by adding 7.5 wt.% of TPA-4PDI in the ternary blend, which photovoltaic performance is enhanced with synergistically increased open-circuit voltage (V oc ) of 0.849 V, short-circuit current density (J sc ) of 27.55 mA cm −2 , and fill factor (FF) of 78.21%. TPA-4PDI exhibits a complementary absorption band with PM6 and Y6 while its lowest unoccupied molecular orbital (LUMO) energy level falls between the two host materials. The addition of TPA-4PDI can effectively suppress the recombination behavior, inhibit the excessive aggregation of Y6 and improve the morphology of PM6:Y6 blend. All these effects function synergistically and then lead to the enhancement of V oc, J sc , and FF in ternary OSCs. This study suggests that developing PDI derivatives as the third component is an effective method to further improve the performance of ternary OSCs.

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their high efficiency and low-cost solution manufacturing procedure and are considered the most likely to be commercialized and could be compared with silicon-based solar cells. The power conversion efficiencies (PCEs) of PSCs have increased dramatically from 3.8% to 25.7% [1][2][3] during the last decade with the advancements in fabrication techniques, [4][5][6] chemical compositions, [7,8] and phase stabilization techniques. [9,10] However, ion migration, electrode degradation, energy level mismatch, and poor interface contact are still the limited factors that needed to be considered and optimized. [11][12][13] Among them, interfacial contact defect is the most important challenge to be solved for the state-of-the-art PSCs. To this end, a lot of research have been done on interface engineering to reduce interface defects in order to higher photovoltaic performance of PSCs. [14,15] At present, the solution processed [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) is still used as benchmark electron transport material (ETM) in inverted PSCs because it can effectively passivate the charge trap states and defects on the surface of perovskite layer. [16,17] However, the PC 61 BM as ETL suffers from the larger energy level barrier with high-work function cathode (i.e., Ag) and leads to significant energy loss at PC 61 BM/Ag interface. Moreover, solution-processed PC 61 BM as cathode interface layer (CIL) also suffers from obvious aggregations with large roughness, leading to poor interface contact with Ag cathode and large charge recombination in PSCs.To correct the energy level mismatch and poor interface, an appropriate CIL need to be inserted between PC 61 BM and Ag electrode. [18,19] The CIL as a functional layer in PSC together with electron transport layer (ETL) plays the vital role of charge carrier extraction and transport, which can also modify the interfacial properties of ETL and lower the work function (WF) of the metal electrode. [20,21] Among cathode interface materials (CIMs), solution processable organic small molecules and polymers offer a more convenient device preparation process than alkaline salts (i.e., LiF) and metal oxides (i.e., ZnO, TiO 2 ), which normally require vacuum thermal evaporation or thermal annealing.In inverted perovskite solar cells (PSCs), n-doping fullerene electron transport layers (ETLs) have been found to prepare high efficiency devices due to their excellent performance in electrochemistry, film formability, and surface passivation. Herein, two cathode interface layers (CILs) 2PDI-FN and 2PDIT-FN are prepared with dimethylamino functional groups and PDI units. The addition of thiophene makes the 2PDIT-FN conjugated framework coplanar and enhances the effect of dimethylamino functional groups, which give 2PDIT-FN with higher electrical conductivity, electron mobility, self-doping property, and film formability. Moreover, dopant N-DMBI can further enhance these advantages of 2PDIT-FN. Consequently, a peak power conversion efficiency (PCE) of 20.44% is achieved with 2P...

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