Decoupling Bulk Energetics and Interfacial Passivation in Low‐Temperature TiO 2 for High‐Performance Carbon Electrode‐Based Perovskite Solar Cells
Warunee Khampa, Woraprom Passatorntaschakorn, Wongsathon Musikpan, Chukwuebuka Emmanuel Usulor, Sukhanidhan Singh, Isaac Chinaza Ogbuagu, Athipong Ngamjarurojana, Ratchadaporn Supruangnet, Hideki Nakajima, Pongsakorn Kanjanaboos, Anusit Kaewprajak, Pisist Kumnorkaew, Pipat Ruankham, Duangmanee WongratanaphisanAchieving high‐efficiency carbon electrode‐based perovskite solar cells (CPSCs) with low‐temperature processed TiO 2 electron transporting layers (ETLs) is challenging due to the inferior film quality and elevated defect density associated with conventional sources. Here, we introduce a synergistic dual‐modification strategy that integrates titanium diisopropoxide bis(acetylacetonate) (TDBA) ligand‐assisted TiO 2 network engineering with ultrathin SnO 2 passivation as a hybrid TiO 2 ‐TDBA/SnO 2 ETL to overcome these limitations. TDBA incorporation densifies the TiO 2 framework and enhances the built‐in potential, enabling higher V OC , while the SnO 2 overlayer suppresses interfacial defects and facilitates charge extraction, leading to an improved fill factor (FF). As a result, CPSCs fabricated under dry‐air conditions achieve a PCE of 15.77%. The strategy is further extended to flexible devices, yielding 11.95%, and significantly enhances indoor performance to 27.53% under 1000 lx LED illumination. Additionally, a 6 cm 2 module exhibits scalable performance, with PCEs of 5.41% at one sun and 19.31% in indoor light. This work establishes an effective and scalable interfacial engineering route for low‐temperature TiO 2 ETLs, offering a green and practical pathway toward high‐performance CPSCs for both indoor and outdoor applications.