Stability Improvement of Perovskite Solar Cells by the Moisture-Resistant PMMA:Spiro-OMeTAD Hole Transport Layer

Abstract

Perovskite solar cells (PSCs) based on the 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) hole transport layer have exhibited leading device performance. However, the instability caused by this organic function layer is a very important limiting factor to the further development of PSCs. In this work, the spiro-OMeTAD is doped with polymethyl methacrylate (PMMA), which is further used as the hole transport layer to improve the device stability. It is shown that the PMMA can effectively improve the moisture and oxygen resistance of spiro-OMeTAD, which leads to improved device stability by separating the perovskite layer from moisture and oxygen. The device efficiency can maintain 77% of the original value for PSCs with the PMMA-doped spiro-OMeTAD hole transport layer, under a natural air environment (RH = 40%) for more than 80 days. The results show that the moisture- and oxygen-resistant PMMA:spiro-OMeTAD hole transport layer is effective at improving the device performance.

Understanding the Degradation Factors, Mechanism and Initiatives for Highly Efficient Perovskite Solar Cells

“…The PCE of CH 3 NH 3 PbI 3 /CuI rapidly increases from 13.6% to 16.8% in inverted planar structure comparison to the CH 3 NH 3 PbI 3 /PEDOT: PSS . Ma et al., [143] doped Spiro‐OMeTAD HTL with polymethyl methacrylate (PMMA) of the structure ITO/SnO 2 /Perovskite/PMMA:Spiro‐OMeTAD/Au. With PMMA the original efficiency (21.2%) improved to an extent of 3% in contrast to the efficiency achieved without PMMA (20.6%).…”

Promotion Strategies of Hole Transport Materials by Electronic and Steric Controls for n–i–p Perovskite Solar Cells

“…[98] Besides some polymerization precursors, some polymers were introduced into o-HTLs, also acting as cross-linking additives to cohesive molecules and enhance organization of o-HTMs. [101] Xia et al and Kundu and Kelly used PMMA as additives in spiro-OMeTAD [99] and P3HT, [102] respectively. PMMA additives were considered to not only enhance the morphology of HTLs but also improve the conductivity of HTLs by manipulating their formation behavior (Figure 6 f).…”

“…discovered that 1,3,5,7‐tetrakis‐( p ‐benzylazide)‐adamantane (TPBA) enabled to enhance the solvent resistance and mechanical toughness of PTAA (Figure 6 e), without compromising the electronic functionality of the HTL [98] . Besides some polymerization precursors, some polymers were introduced into o‐HTLs, also acting as cross‐linking additives to cohesive molecules and enhance organization of o‐HTMs [101] . Xia et al.…”

Anion‐Modulated Chemical Doping of Organic Hole Conductor Boosts Efficiency and Stability of Perovskite Solar Cells

“…Recently, great efforts have been devoted to understanding the nature of charge transport in doped materials and exploring alternative molecular structures of OCC for various applications, especially for the emerging perovskite solar cells (PSCs). [ 2,4,5 ] Small molecule 2,2′,7,7′‐tetrakis( N , N ‐di‐p‐methoxyphenyl‐amine)9,9′‐spirobifluorene (spiro) represents the state‐of‐the‐art hole transport material (HTM) in PSCs, undertaking multiple responsibilities of hole transport, carrier selectivity, physical barrier for moisture ingress and metal diffusion, [ 6–8 ] all of which in turn play decisive roles in device efficiency and stability. [ 9,10 ] However, low conductivity (≈5 × 10 −8 S cm −1 ) of pristine undoped spiro hampers charge‐collection yield as well as efficiency of PSCs.…”