Collaborative interfacial modification and surficial passivation for high-efficiency MA-free wide-bandgap perovskite solar cells

The wide-bandgap (WBG) perovskite solar cells (PSCs) are the pivotal component for the tandem solar cells, which provides a potential for exceeding the theoretical power conversion efficiency (PCE) limit of the single-junction solar cells. However, the improvement of PCE for perovskite/silicon tandem solar cells is restricted by the interfacial transport barrier loss and the nonradiative recombination loss of the WBG-PSC top cell. Herein, we applied methylammonium-free (MA-free) WBG perovskite for achieving an excellent stability light absorber. This work offers a simultaneous interfacial modification and surficial passivation strategy for suppressing the losses of interfacial barrier and recombination. The mixture of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and [2-(3,6-dimeth oxy-9H-carbazol-9-yl)ethyl]phosphonic acid (Meo-2PACz) as a self-assembled monolayer (SAM) is employed to facilitate the carrier transport from the perovskite to the anode. 4-trifluoromethyl-phenylammonium iodine (CF3PhAI) is introduced to passivate the surface defect of perovskites. Therefore, the open circuit voltage and PCE of the WBG-PSC are significantly increased. The opaque and transparent electrode (TE) PSCs achieve PCEs of 20.11% and 17.80%, respectively, and the unencapsulated opaque PSC retains more than 85% of the initial efficiency after 1750 h in N2-glovebox. The four-terminal tandem solar cell with perovskite and silicon absorbers was fabricated and obtained 26.59% efficiency. This work provides a simple way to improve the PCE and stability of WBG-PSCs, facilitating the development of tandem solar cells.