Efficient and Stable Vacuum‐Free‐Processed Perovskite Solar Cells Enabled by a Robust Solution‐Processed Hole Transport Layer

Abstract

Here, efficient and stable vacuum-free processed perovskite solar cells (PSCs) are demonstrated by employing solutionprocessed molybdenum tris-[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-COCF ) )-doped poly(3,4-ethylenedioxythiophene) (PEDOT) film as hole transport layer (HTL). Our results indicate that the incorporation of Mo(tfd-COCF ) dopant can induce p-doping through charge transfer from the highest occupied molecular orbital (HOMO) level of the PEDOT host to the electron affinity of Mo(tfd-COCF ) , leading to an increase in conductivity by more than three orders of magnitude. With this newly developed p-doped film as HTL in planar heterojunction PSCs, a high power conversion efficiency (PCE) up to 18.47 % can be achieved, which exceeds that of the device with commonly used HTL 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). Taking the advantage of the high conductivity of this doped film, a prominent PCE as high as 15.58 % is also demonstrated even when a large HTL thickness of 220 nm is used. Importantly, the high quality film of this HTL is capable of acting as an effective passivation layer to keep the underlying perovskite layer intact during solution-processed Ag-nanoparticles layer deposition. The resulting vacuum-free PSCs deliver an impressive PCE of 14.81 %, which represents the highest performance ever reported for vacuum-free PSCs. Furthermore, the resulting devices show good ambient stability without encapsulation.

Doping strategies for small molecule organic hole-transport materials: impacts on perovskite solar cell performance and stability

“…Molybdenum-based dopants are well-known and used to dope a number of p-type organic materials 138,139. Previously, molybdenum-based dopants have been successfully used for doping polymer-based HTLs, such as P3HT138 and PEDOT 139.…”

“…Molybdenum-based dopants are well-known and used to dope a number of p-type organic materials 138,139. Previously, molybdenum-based dopants have been successfully used for doping polymer-based HTLs, such as P3HT138 and PEDOT 139. With respect to small-molecule HTLs, solution-processable molybdenum tris(1-(methoxycarbonyl)-2-(trifluoromethyl)ethane-1,2-dithiolene) (Mo(tfd-CO 2 Me) 3 ) and molybdenum tris(1-(trifluoroacetyl)-2-(trifluoromethyl)ethane-1,2-dithiolene) (Mo(tfd-COCF 3 ) 3 ) were assessed by Pellaroque et al 140 This is not commercially available, and dopant synthesis required three simple steps with moderate yields 138,141.…”

Organic/Inorganic Hybrid EIL for All‐Solution‐Processed OLEDs

“…Unfortunately, it is difficult to characterize the solvent‐proof capability. The usual subjective judgement is not accurate enough …”

Effects of Cyclic Tetrapyrrole Rings of Aggregate-Forming Chlorophyll Derivatives as Hole-Transporting Materials on Performance of Perovskite Solar Cells

“…Hole-transporting materials (HTMs) are essential components of PSCs that block the flow of electrons to the anode side and efficiently extract holes generated in the perovskite layer. , The most widely used HTMs are organic small molecules and polymers, such as 2,2′,7,7′-tetrakis­( N , N -di- p -methoxyphenylamine)-9,9′-spirobifluorene , and poly­(3-hexylthiophene), − which are relatively expensive. The development of cost-effective HTMs is crucial. − …”