Highly reproducible self-assembled monolayer based perovskite solar cells via amphiphilic polyelectrolyte

Self-assembled monolayers (SAM) have attracted a lot of attention in perovskite solar cells (PSCs) due to their high efficiency in both single junction and tandem devices. However, inferior reproducibility originating from poor surface coverage and voids in the perovskite layer at the buried interface still limits their widespread use. Herein, we report a facile method to significantly improve the reproducibility of PSCs by employing an amphiphilic conjugated polyelectrolyte between SAMs and perovskite layers. Application of the polyelectrolyte leads to a 200 meV shallower perovskite Fermi level, allowing a desirable, significantly increased band bending at the SAM/perovskite interface. Moreover, imaging the buried perovskite interface by a novel technique reveals that interfacial voids are minimised by the polyelectrolyte leading to complete coverage of the ITO/SAM surface. As a result, remarkable fill factors over 0.84 and power conversion efficiencies exceeding 22.5% are achieved. The PSCs demonstrate exceptional reproducibility and high performance, as evidenced by an average fill factor of 0.81 with a remarkably low standard deviation of less than 0.01 across 50 individual devices. These results demonstrate a universal method to improve the reproducibility of PSCs containing commonly used SAMs and open the door for wider use of amphiphilic conjugated polyelectrolytes in optoelectronic devices.