Improved Efficiency and Stability of Perovskite Solar Cells by Binary Perovskite–Organic Composite Thin Film

Regulating perovskite film crystallization and avoiding bulk defects during the deposition process are essential for achieving perovskite solar cells (PSCs) with excellent power conversion efficiency (PCE) and stability. Herein, the synergistic effects between n‐type, narrow‐bandgap conjugated organic molecules (2,2′‐((2 Z ,2′ Z )‐((5,5′‐(4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydros‐indaceno[1,2‐b:5,6‐ b ′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile [IEICO]) and perovskites on film surface morphology and stability, and the regulation mechanism on bulk defects in MAPb(I 0.97 Br 0.03 ) 3 :IEICO films are explored. The results of theoretical and experimental studies indicate that a large number of electrons on the CO and C≡N surface functional groups of IEICO can function as Lewis bases and exhibit strong interactions with uncoordinated Pb 2+ ions, substantially reducing bulk defects. Moreover, the resulting MAPb(I 0.97 Br 0.03 ) 3 :IEICO film exhibits an optical response in the near‐infrared region and an increased crystallite size. Consequently, the MAPb(I 0.97 Br 0.03 ) 3 :IEICO PSCs with a p–i–n device structure demonstrate a PCE exceeding 20%. In addition, the MAPb(I 0.97 Br 0.03 ) 3 :IEICO PSCs possess superior stability and negligible photocurrent hysteresis. These results suggest that the incorporation of near‐infrared organic molecules into perovskites provides a simple method to achieve high‐performance PSCs and realize the utilization of near‐infrared wavelengths.