Organic N-Type Molecule: Managing the Electronic States of Bulk Perovskite for High-Performance Photovoltaics
Haiyang Chen1, Yu Zhan1, Guiying Xu1, Weijie Chen1, Shuhui Wang1, Moyao Zhang1, Yaowen Li1，*（李耀文）, and Yongfang Li1，2
1Laboratory of Advanced Optoelectronic Materials，College of Chemistry，Chemical Engineering and Materials Science，Soochow University，Suzhou 215123, China
2Beijing National Laboratory for Molecular Sciences，Institute of Chemistry，Chinese Academy of Sciences，Beijing 100190, China
Adv. Funct. Mater. 2020, 2001788
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 MAPbI3 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.