Organic N-Type Molecule: Managing the Electronic States of Bulk Perovskite for High-Performance Photovoltaics

The power conversion efficiency (PCE) of planar p-i-n perovskite solar cells (pero-SCs) is commonly lower than that of the n-i-p pero-SCs, due to the severe nonradiative recombination stemming from the more p-type perovskite with prevailing electron traps. Here, two n-type organic molecules, DMBI-2-Th and DMBI-2-Th-I, with hydrogen-transfer properties for the doping of bulk perovskite aimed at regulating its electronic states are synthesized. The generated radicals in these n-type dopants with high-lying singly occupied molecular orbitals enable easy transfer of the thermally activated electrons to the MAPbI(3)perovskite for the realization of n-doped perovskites. The n-doping degree could be further enhanced by using the iodine ionized dopant DMBI-2-Th-I. The doping effect could reduce the electron trap density, increase the electron concentration of the bulk perovskite, and simultaneously improve the surface electronic contact. When the DMBI-2-Th-I-doped perovskite is used in planar p-i-n pero-SCs, the nonradiative recombination is significantly suppressed. As a result, the photovoltaic performance improved significantly, as evidenced by an excellent PCE of 20.90% and a robust ambient stability even under high relative humidity. To the best of the knowledge, this work represents the first example where organic n-type dopants are used to tune the electronic states of a bulk perovskite film for efficient planar p-i-n pero-SCs.