Composition and Interface Engineering for Efficient and Thermally Stable Pb–Sn Mixed Low‐Bandgap Perovskite Solar Cells

Abstract

Low bandgap lead-tin mixed perovskite solar cells have achieved high power conversion efficiency in excess of 17%. However, methylammonium (MA) cation was usually contained, and the thermal stability of MA is always a great concern. In this work, accoring to composition engineering, we tried to explore a nearly formamidinium (FA) based lowbandgap Pb-Sn mixed perovskite FAPb 0.75 Sn 0.25 I 3 as the absorber layer. Combined with interface enginering by replacing PEDOT:PSS layer with NiO x as hole transport layer, a power conversion efficiency of 17.25% has been obtained. This low-bandgap perovskite solar cell maintains about 91% of its original efficiency at 80 O C for 20 hours, and 92% of its initial performance after 46 days storage at the room temperature. The good thermal stability of nearly FA based low-bandgap perovskite could be good for delivering efficient and stable perovskite-perovskite tandem solar cells.

Low‐Bandgap Mixed Tin‐Lead Perovskites and Their Applications in All‐Perovskite Tandem Solar Cells

“…On the other hand, devices with high Pb contents show S‐shape J–V curves ( Figure a), which might be due to the interface charge transport barrier and the absence of the hole‐blocking layer. Recently, Chi and co‐workers reported that in the device structure of ITO/PEDOT:PSS/FASn x Pb 1− x I 3 /PC 60 BM/BCP/Ag, the composition of FAPb 0.75 Sn 0.25 I 3 has the best performance with a bandgap of 1.36 eV (Figure b) . They also found that employing inorganic NiO x HTL to replace PEDOT:PSS could improve the performance of FAPb 0.75 Sn 0.25 I 3 based PSCs due to the well‐matching band alignment, and a PSC with a PCE of 17.25% was achieved .…”

“…Recently, Chi and co‐workers reported that in the device structure of ITO/PEDOT:PSS/FASn x Pb 1− x I 3 /PC 60 BM/BCP/Ag, the composition of FAPb 0.75 Sn 0.25 I 3 has the best performance with a bandgap of 1.36 eV (Figure b) . They also found that employing inorganic NiO x HTL to replace PEDOT:PSS could improve the performance of FAPb 0.75 Sn 0.25 I 3 based PSCs due to the well‐matching band alignment, and a PSC with a PCE of 17.25% was achieved . In addition, Wu and co‐workers reported efficient FAPb 0.7 Sn 0.3 I 3 based low‐bandgap PSCs fabricated using a two‐step method combining with a bifunctional additive of methylammonium thiocyanate (MASCN), as shown in Figure c …”

δ‐CsPbI3 Intermediate Phase Growth Assisted Sequential Deposition Boosts Stable and High‐Efficiency Triple Cation Perovskite Solar Cells

“…Generally, the A site is occupied by a monovalent organic or inorganic cation (e.g., CH 3 NH 3 + (MA); HC(HN 2 ) 2 + (FA); Cs + ; Rb + ), the B is often a metal cation (e.g., Pb 2+ ; Sn 2+ ), and the X is typically a halide anion (e.g., Cl‐; Br – ; I – ; SCN – ). Compositional engineering of the hybrid metal halide perovskite or inorganic perovskite materials with mixed cations and halides is an effective strategy to achieve further improvements in PCE and long‐term stability of the devices …”

Realizing High Efficiency over 20% of Low‐Bandgap Pb–Sn‐Alloyed Perovskite Solar Cells by In Situ Reduction of Sn4+

“…Many efforts have been devoted to improving the PCE of low‐bandgap mixed Pb–Sn PSCs . However, it often exhibits a larger open‐circuit voltage ( V oc ) loss, and therefore, its efficiency is far behind that of pure Pb‐based PSCs with a medium bandgap.…”