Efficient and Fully Non-Halogen Solution Processed Cs2AgBiBr6 Perovskite Solar Cell

For traditional hole transport material (HTM) 2,2 ',7,7 '-tetrakis(N,N '-di-pmethoxyphenylamino)9,9 '-spirbiuorene (Spiro-OMeTAD) used in Cs2AgBiBr6 perovskite solar cell (PSC), the strong dependence of its performance on the hygroscopic and volatility additives, together with the mismatched energy level with Cs2AgBiBr6 and gold electrodes, are considered to be the two key factors restricting the improvement of performance. Considering this, we reported a series of dopant-free D-it-D type HTMs comprising of FNP as donor unit and Cz-Mp dimer linked benzene as it-bridge, termed o- PCz , m- PCz , and p- PCz by adjusting the linkage position of it-bridge moieties. HTM p-PCz with planar rigid structure, exhibits higher hole mobility and better film morphology compared with o- PCz and m- PCz . Notably, o- PCz , m- PCz , and p- PCz all show good dissolvability in non- halogenated solvent tetrahydrofuran (THF), making it possible to fabricate Cs2AgBiBr6 PSCs with full non- halogenated solution process. As a result, the dopant-free p-PCz based Cs2AgBiBr6 PSC device achieved an efficiency of 2.44 % with enhanced ambient and thermal stability. Hence, the successful development of dopantfree p-PCz would make a great contribution for efficient and stable lead-free Cs2AgBiBr6 PSCs with full non- halogenated solution process.