Binary hole transport layer enables stable perovskite solar cells with PCE exceeding 24%
Xiao Chen, Bing Guo, Zeyu Zhang, Bo Zhang, Xinzhi Zu, Nabonswendé Aïda Nadège Ouedraogo, Jiyeon Oh, Yongjoon Cho, George Omololu Odunmbaku, Kun Chen, Yongli Zhou, Shanshan Chen, Changduk Yang, Juan Du, Kuan Sun
Abstract
Hygroscopic dopant in hole transport layer (HTL) is a key factor contributing to moisture-induced perovskite degradation and the resulting performance loss over time. This poses obstacles to the commercialization of perovskite solar cells (PSCs). Herein, we mixed two popular hole transport materials, i.e., [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene] (Spiro-OMeTAD) and poly (3-hexylthiophene-2,5-diyl) (P3HT), to form a binary mixed HTL. Due to the presence of hydrophobic P3HT component, the mixed HTL exhibits improved moisture resistance. In addition, P3HT demonstrates a great ability to interact with the dopants, which changes π-π packing orientation of P3HT from edge-on to face-on and improves its crystallinity, thus increasing hole mobility and hole extraction capability of the mixed HTL. As a result, PSCs equipped with the Spiro-OMeTAD/P3HT mixed HTL exhibit a champion power conversion efficiency (PCE) up to 24.3% and superior operational stability. The cells without encapsulation can maintain 90% initial efficiency after storage in dark ambient conditions (30% RH) for 1200 h. These results suggest that constructing Spiro-OMeTAD/P3HT mixed HTL is a promising strategy to meet the future photovoltaic applications demands with low-cost as well as excellent efficiency and device stability.