Vertically oriented micron-thick perovskite film enables efficient and stable inverted perovskite solar cells

Chemical and physical modification at buried perovskite interface is of great importance for realizing efficient perovskite solar cells (PSCs), as it directly affects the perovskite crystallization process and charge transfer. In this work, an amidine-terminated molecule, ethyl 2-amidinoacetate hydrochloride (E-2AH), was adopted to modulate the crystallization kinetics of perovskites at the buried perovskite interface, which induces vertically oriented growth and passivation of the defects within perovskite films. E-2AH molecules strongly interact with undercoordinated lead ions, which in turn retard the crystallization process and remove the intermediate phase, resulting in the formation of micron-thick perovskite film with suppressed nonradiative recombination and enhanced charge extraction. The target small area (0.04 cm2) PSCs exhibit a champion power conversion efficiency (PCE) of 25.25 % while the mini-modules with an aperture area of 15 cm2 obtain a PCE of 21.25 % (certified as 21.29 %). Moreover, the unencapsulated devices maintain 95 % of the initial PCE after 2400 h of storage in an N2 atmosphere and obtain over 90 % of initial PCE after 300 h at maximum power point tracking. This work established an efficient way to improve performance of inverted PSCs by directing the oriented growth of perovskite crystalline grains through interface engineering.