Efficient and stable organic solar cells enabled by incorporation of titanium dioxide doped PEDOT:PSS as hole transport layer

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely served as the state-of-art hole transport layer (HTL) for high performance organic solar cells (OSCs) due to its easy solution processability, excellent hole extraction ability, and well compatibility with various active layers. However, PEDOT:PSS shows several drawbacks such as relatively moderate conductivity and optical transparency, acidity, and reactivity, which directly limits the improvement of device performance and leads to the deterioration of device stability. In this work, metal oxide titanium dioxide (TiO2) was doped into the conventional HTL-material PEDOT:PSS, which simultaneously boosted the power conversion efficiency (PCE) and stability of OSCs based on PBDB-T:N2200. The simultaneous improvement in PCE and stability is originated from the effectively improved light transmittance and conductivity of PEDOT:PSS, increased hole extraction of the active layer, as well as the optimized ohmic contact between the interface layer and the electrode. In addition, the TiO2 doping PEDOT:PSS strategy is proved to be general to a variety of OSCs systems, which is expected to bring new opportunities for the development of high performance HTL, so as to promote the commercialization of OSCs.