Surface Modification of NiOx Layer with Versatile Coupling Agent Enables Enhanced Performance and Stability of Inverted Perovskite Solar Cells

In recent years, nickel oxide (NiOx) is widely used as an excellent hole transport layer for the inverted perovskite solar cells (PSCs), due to its decent hole conductivity, easy processability, and low cost. However, the photovoltaic performance and stability of NiOx-based PSCs are severely limited by the poor perovskite/NiOx interface. Herein, a versatile coupling agent di(dioctylpyrophosphato) ethylene titanate (NDZ-311) is introduced to improve the performance of NiOx-based inverted PSCs by suppressing nonradiative recombination and strengthening charge transfer at the perovskite/NiOx interface. Moreover, the chemical reaction between NDZ-311 and NiOx reduces the surface hydroxyl groups of NiOx film and avoids direct contact between perovskite and NiOx film, which mitigate material degradation caused by high-valence Ni ions and hydroxyl groups. As a result, the average power conversion efficiency (PCE) of inverted PSCs is enhanced from approximate to 18.01% to approximate to 19.92% and a maximum PCE of approximate to 20.39% is obtained. The unencapsulated PSC with NDZ-311 modification maintains 87.65% of their initial performance after 400 h aging test in air, much better than the control device (49.41% after 400 h). The work demonstrates the potential application of NDZ-311 for commercial PSCs, considering NDZ-311 is a cheap industrial material.