Layered bismuth selenide utilized as hole transporting layer for highly stable organic photovoltaics

Abstract Layered bismuth selenide (L-Bi 2 Se 3 ) nanoplates were implemented as hole transporting layers (HTLs) for inverted organic solar cells. Device based on L-Bi 2 Se 3 showed increasing power conversion efficiency (PCE) during ambient condition storage process. A PCE of 4.37% was finally obtained after 5 days storage, which outperformed the ones with evaporated-MoO 3 using poly(3-hexylthiophene) (P3HT) as donor material and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) as acceptor. The improved device efficiency can be attributed to the high conductivity and increasing work function of L-Bi 2 Se 3 . The work function of L-Bi 2 Se 3 increased with the storage time in ambient condition due to the oxygen atom doping. Ultraviolet photoelectron spectroscopy and high resolution X-ray photoelectron spectroscopy were conducted to verify the increased work function, which originated from the p-type doping process. The device based on L-Bi 2 Se 3 exhibited excellent stability in ambient condition up to 4 months, which was much improved compared to the device based on traditional HTLs.