미래를 창조하는 포스텍 화학공학과
Perovskite solar cells (PSCs) have reached their highest efficiency with 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). However, this material can cause problems with respect to reproducibility and stability. Herein, we report a solution-processable inorganic-organic double layer based on tungsten oxide (WO3) and spiro-OMeTAD as a hole transport layer in PSCs. The device equipped with a WO3/spiro-OMeTAD layer achieves the highest efficiency (21.44%) in the tin (IV) oxide planar structure. The electronic property of the double layer is thoroughly analyzed using photoluminescence, space-charge-limited current, and electrochemical impedance spectroscopy. The WO3/spiro-OMeTAD layer exhibits better hole extraction ability and faster hole mobility. The WO3 layer particularly improves the open-circuit voltage (VOC) by lowering the quasi-Fermi energy level for holes and reducing charge recombination, resulting in high VOC (1.17 V in the champion cell). In addition, the WO3 layer as a scaffold layer promotes the formation of a uniform and pinhole-free spiro-OMeTAD overlayer in the WO3/spiro-OMeTAD layer. High stability under thermal and humid conditions stems from this property. Our study presents a facile approach for improving the efficiency and stability of PSCs by stacking an organic layer on an inorganic layer.