Highly efficient and durable planar carbon-based perovskite solar cells enabled by polystyrene modified hole-transporting layers

Abstract

The efficiency and durability of perovskite solar cells (PSCs) are closely related to the property and stability of each functional layer involved in device. Owing to the excellent hole transport properties, the additive-doped Spiro-OMeTAD (2,2′,7,7′-tetrakis (N,N-di-p-methoxyphenylamine) 9,9′-spirobifluorene) has become an excellent hole-transporting material for obtaining highly efficient PSCs. However, the hygroscopic nature of additives and the pinholes caused by poor film-forming capability inevitably impair the performance and long-term stability of Spiro-OMeTAD and the resulting PSCs. In this study, the hydrophobic polymer polystyrene (PS) was incorporated to improve the hydrophobicity and film-forming capability of the additive-doped Spiro-OMeTAD films. Based on the PS-modified Spiro-OMeTAD and carbon electrodes, the derived planar carbon-based PSCs exhibited significantly enhanced long-term stability, which can maintain 92% of its initial efficiency after aging for 2500 h under ambient atmosphere without encapsulation. In addition, the PS-modified Spiro-OMeTAD exhibited improved morphology with reduced pinholes, contributing to significantly enhanced interfacial carrier transport. Finally, a champion power conversion efficiency of 21.06% was obtained, which is one of the highest efficiencies reported for the planar carbon-based PSCs to date.