2022 Adv. Mater., A Selective Targeting Anchoring Strategy for Efficient and Stable Ideal- Bandgap Perovskite Solar Cells
Selective targeted anchoring strategy can fabricate efficient and stable ideal-bandgap perovskite solar cells. Strategy of molecule selective targeting anchoring (STA) was established, employing phenethylammonium iodide (PEAI) and ethylenediaminediiodide (EDAI) as co-modifiers to selectively anchor with Pb- and Sn-related active sites and passivate bimetallic traps, respectively. Through DFT calculations and optoelectronic techniques, it is demonstrated that Pb- and Sn-related A-site vacancies are pushed into deeper energy depths, leading to severe nonradiative recombination.
The Voc of the mixed lead–tin perovskite solar cells (LTPSCs) is significantly increased from 0.79 V to 0.90 V, and a champion efficiency of 22.51% is obtained, which is the highest efficiency among the reported ideal-bandgap PSCs. The Voc loss is reduced to 0.43 V.
The perovskite band gap can be reduced by partially or completely replacing Pb with Sn. When the Sn ratio is 20%, the band gap can be reduced to an ideal value of about 1.33 eV. However, the 20% Sn content is the critical value of perovskite bandgap change, in which there are many defects, resulting in severe open-circuit voltage loss (VOC loss) caused by non-radiative recombination. According to previous research, there are two main reasons for the loss of open circuit voltage:
- Sn2+ is easily oxidized to Sn4+, causing severe self-p-doping, forming Sn vacancies, and introducing additional p-type charges.
- The reaction of Sn with organic components is stronger than that of Pb, which makes the crystallization process too fast and uncontrolled, resulting in poor film quality and increased defect density.
By passivating perovskite through a directional selective anchoring strategy, the researchers achieved a record PCE of 22.51% for ideal-bandgap PSCs. The findings suggest that the defects of bimetals in LTPSCs are the main cause of their performance degradation. Therefore, the researchers used PEAI and EDAI as co-modifiers for surface treatment of perovskites. The active site sites associated with Pb and Sn were selectively anchored and passivated for the two metal defects, respectively. The open-circuit voltage (VOC) of the final lead-tin hybrid perovskite solar cell is greatly increased from 0.79 V to 0.90 V, and the loss of open-circuit voltage is reduced to 0.43 V. In addition, the devices exhibited excellent stability, maintaining 80% initial PCE after storing for 2700h in nitrogen glove box. This work provides an efficient passivation mechanism for managing metal dual-source defects in LTPSCs.
Keywords: Selective Targeting Anchor, Ideal-Bandgap Perovskite Solar Cell, Solar Simulator, Sun Simulator