D-p-D molecular layer electronically bridges the NiOx hole transport layer and the perovskite layer towards high performance photovoltaics

Nickel oxide (NiOx) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine] (PTAA) for inverted p-i-n perovskite solar cells (PSCs), but the poor NiOx/perovskite contact stemming from some reactive species at the interface led to suboptimal device performance. To solve this problem, we take a multiple donor molecule approach, using 3,3'-(4,8-bis(hexylthio)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(10-(6-bromohexyl)-10H-phenoxazine) (BDT-POZ) as an example, to modify the NiOx/perovskite interface. The primary goal was to reduce the under-coordinated Ni >= 3+ cations via electron transfer from the donor molecules to NiOx, thus mitigating the detrimental reactions between perovskite and NiOx. Equally importantly, the hole extraction at the interface was greatly enhanced after the organic donor modification, since the hydrophobic species atop NiOx not only enabled pinhole-free crystallization of the perovskite but also properly tuned the interfacial energy level alignment. Consequently, the PSCs with NiOx/BDT-POZ HTL achieved a high power conversion efficiency (PCE) up to 20.16%, which compared excellently with that of the non-modified devices (17.83%). This work provides a new strategy to tackle the exacting issues that have so far impeded the development of NiOx based PSCs. (c) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

A new strategy of modifying the nickel oxide/perovskite interface using multiple donor molecules was proposed to improve the performance of nickel oxide-based perovskite solar cells. The modified cells achieved a high power conversion efficiency of 20.16%.