Amino acid modified Ti3C2Tx as electron transport layers for high-performance organic solar cells

The Ti 3 C 2 T x , as a typical representative of the MXene family, has attracted much attention due to excellent properties in terms of transmittance, conductivity, tunable work function (WF), and low temperature solution processability . However, the work function that needs to be adjusted and a large number of crystal defects in Ti 3 C 2 T x greatly restrict its use in electronic devices. Herein, Ti 3 C 2 T x is modified with amino acids to modulate WF of Ti 3 C 2 T x and passivate its defect sites , thereby improving the electrical properties of Ti 3 C 2 T x and enhancing the performance of organic solar cells (OSCs). Amino acids interact with Ti 3 C 2 T x by charge transfer and forming a surface dipole on the surface, which reduces the WF of Ti 3 C 2 T x . Moreover, -NH 2 of amino acids passivates the negatively charged Ti vacancies in Ti 3 C 2 T x , while -COOH of amino acids passivates the positively charged C vacancies, increasing the conductivity of Ti 3 C 2 T x . Consequently, the OSCs with amino acid-modified Ti 3 C 2 T x -based as new electron transport layer (ETL) exhibit more than 18% of power conversion efficiency (PCE) and good device stability. The work shows OSCs with high performance can be fabricated by using environmental-friendly amino acids, which inspires researchers to seek ideas for fabricating efficient devices from natural materials.