An excellent organolead halide perovskite film is important for the good performance of perovskite solar cells (PSCs). However, defects in perovskite crystals can affect the photovoltaic properties and stability of solar cells. To solve this problem, this study incorporated a complex of CdS and Cd(SCN 2 H 4 ) 2 Cl 2 into the CH 3 NH 3 PbI 3 active layer. The effects of different doping concentrations of CdS and Cd(SCN 2 H 4 ) 2 Cl 2 on the performance and stability of PSCs were analyzed. Results showed that doping appropriate incorporation concentrations of CdS and Cd(SCN 2 H 4 ) 2 Cl 2 in CH 3 NH 3 PbI 3 can improve the performance of the prepared solar cells. In specific, CdS and Cd(SCN 2 H 4 ) 2 Cl 2 can effectively passivate the defects in perovskite crystals, thereby suppressing the charge recombination in PSCs and promoting the charge extraction at the TiO 2 /perovskite interface. Due to the reduction of perovskite crystal defects and the enhancement of compactness of the CdS:Cd(SCN 2 H 4 ) 2 Cl 2 :CH 3 NH 3 PbI 3 composite film, the stability of PSCs is significantly improved.
Liangxin Zhu,Chong Chen,Fumin Li,Zhitao Shen,Yujuan Weng,Qingsong Huang,Mingtai Wang
To improve the charge separation and transport efficiency in perovskite solar cells (PSCs) with a TiO2-based hybrid mesoscopic/planar architecture, CdS and Cd(SCN2H4)2Cl2 are incorporated into the CH3NH3PbI3 active layer through in situ synthesis to prepare CdS:Cd(SCN2H4)2Cl2:CH3NH3PbI3 bulk-heterojunction films for PSCs. The incorporated CdS and Cd(SCN2H4)2Cl2 improve the quality of perovskite films. Moreover, Cd(SCN2H4)2Cl2 can effectively reduce the defect state density on the CH3NH3PbI3 crystal surface, which decreases charge recombination and facilitates charge transport in PSCs. Furthermore, first-principles calculations show that the I atom of CH3NH3PbI3 has a strong interaction with the Cd atom of CdS, which induces interfacial charge redistribution and charge transfer at the CH3NH3PbI3/CdS interface and therefore decreases the energy of the CH3NH3PbI3:CdS composite system, leading to more efficient electron–hole separation and improved structural stability of the perovskite bulk-heterojunction film. For the above reasons, the CdS:Cd(SCN2H4)2Cl2:CH3NH3PbI3 bulk-heterojunction cell shows much higher efficiency and better stability than the PSCs with pure CH3NH3PbI3. The highest efficiency reaches 20.1%, which is 1.16 times that (17.3%) of the PSCs with pure CH3NH3PbI3 and is also much higher than those of previously reported CH3NH3PbI3 PSCs with a compact/mesoporous TiO2 film. Our research results may provide a new understanding for improving the structural stability and performance of PSCs.
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