Poly(3,4-Ethylenedioxythiophene) as a Hole-Transport Layer for Highly Efficient and Stable Inverted Perovskite Solar Cells

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a well-known hole transport material, and widely used in inverted perovskite solar cells (PSCs). However, its high acidity and hydrophilicity from PSS can corrode the adjacent electrode and perovskite layer, seriously reducing the device performance and durability. Herein, a PEDOT film is fabricated by reactive vapor deposition method, where 5-bromo-2,3-dihydro-thieno[3,4-b][1,4]dioxine as monomer is evaporated and self-polymerized on a substrate at ambient pressure and low temperatures without external oxidants. The resulting PEDOT film is uniform and smooth with high conductivity, and the corresponding inverted CH3NH3PbI3 (MAPbI3) PSC exhibits superior device performance with a PCE of 21.34 %, which is one of the best efficiencies reported for the inverted PSCs with PEDOT:PSS as HTMs. Moreover, a general issue related to the acidic nature of PSS is successfully resolved, and the target device without encapsulation retained more than 80 % of the initial efficiency after 1000 h at ∼ 30 °C and 50 % RH, and kept about 80 % of the initial efficiency after 100 h in N2 atmosphere at 80 °C. This report may provide a facile and effective method for the PEDOT fabrication applied for perovskite solar cells and other optoelectronic devices with high performance and stability.