High-Performance and Stable Perovskite/Organic Tandem Solar Cells Enabled by Interconnecting Layer Engineering.

Perovskite/organic tandem solar cells (PO-TSCs) have recently attracted increasing attention due to their high efficiency and excellent stability. The interconnecting layer (ICL) is of great importance for the performance of PO-TSCs. The charge transport layer (CTL) and the charge recombination layer (CRL) that form the ICL should be carefully designed to enhance charge carrier extraction and promote charge carrier recombination balance from the two subcells. Here, we propose an effective strategy to optimize the ICL by using [2-(9-carbazol-9-yl)ethyl]phosphonic acid (2PACz) to modify the poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as the hole transport layer (HTL) in the ICL. It is found that the coverage state of 2PACz on the PEDOT:PSS significantly affects the performance of PO-TSCs and can be regulated by adjusting the concentration of the 2PACz solution. The PEDOT:PSS/2PACz structure facilitates effective charge carrier extraction from the organic solar cells to the CRL. Herein, for the PO-TSCs, this strategy results in an efficient and balanced charge carrier recombination in the ICL and also allows a thinner PEDOT:PSS with reduced parasitic absorption. As a result, the PO-TSC achieves a power conversion efficiency (PCE) of 25.26%, much higher than the control device (PCE of 23.57%), and better stability. This work demonstrates an effective approach to achieving high-performance PO-TSCs through ICL engineering.