Design of hole-transport-material free CH3NH3PbI3/CsSnI3 all-perovskite heterojunction efficient solar cells by device simulation

The hole-transport-material (HTM) free perovskite solar cells (PSCs) have drawn great attentions due to the simple structure, low fabrication cost and long term stability. However, the photoelectric conversion efficiency (PCE) of the HTM-free PCSs are still low comparing with the traditional sandwich type PSCs. In this work, a new HTM-free PSC is proposed with CH3NH3PbI3/CsSnI3 all-perovskite heterojunction as light-harvester and carbon as back electrode through simulation using the wxAMPS tools. The results are analyzed and compared with the traditional HTM-free perovskite solar cells. It reveals that the narrow band gap CsSnI3 broadens the absorption spectrum to near-infrared region and the high hole mobility favors efficient hole transfer. The optimal performance is achieved as Voc = 1.08 eV, Jsc = 25.33 mA/cm(2), FF = 79.27%, PCE = 21.64%. Comparing to the bare CH3NH3PbI3 absorbing layer, the device efficiency of CH3NH3PbI3/CsSnI3 heterojunction is improved from 18.29% to 21.64%. This indicates that the proposed HTM-free PSC is promising for future photovoltaic and optoelectronics applications.