Transporting holes stably under iodide invasion in efficient perovskite solar cells
Tao Wang, Yao Zhang, Weiyu Kong, Liang Qiao, Bingguo Peng, Zhichao Shen, Qifeng Han, Han Chen, Zhiliang Yuan, Rongkun Zheng, Xudong Yang
Abstract
Highly efficient halide perovskite solar cells generally rely on lithium-doped organic hole transporting layers that are thermally and chemically unstable, in part because of migration of iodide anions from the perovskite layer. We report a solution strategy to stabilize the hole transport in organic layers by ionic coupling positive polymer radicals and molecular anions through an ion-exchange process. The target layer exhibited a hole conductivity that was 80 times higher than that of the conventional lithium-doped layer. Moreover, after extreme iodide invasion caused by light-soaking at 85°C for 200 hours, the target layer maintained high hole conductivity and well-matched band alignment. This ion-exchange strategy enabled fabrication of perovskite solar cells with a certified power conversion efficiency of 23.9% that maintained 92% under standard illumination at 85°C after 1000 hours.