Gi Soon Park Lee, SeungJe Kim, Da-Seul Park, Sang Yeun Koh, Jai Hyun Won, Da Hye Lee, Phillip Do, Young Rag Min, Byoung Koun 2024-01-19T10:04:38Z 2024-01-19T10:04:38Z 2023-01-26 2023-02 1614-6832 https://pubs.kist.re.kr/handle/201004/114057 Ultrathin solar cells (UTSCs) have attracted much research attention because of their superior potential for low-cost production and diverse applications. For UTSCs to achieve high efficiency, rear-interface passivation is critical because it has greater influence on thinner absorbers. Conventional passivation layers (e.g., Al2O3 and SiO2) inevitably require patterned contact openings for electrical conduction, the complex processing of which severely impedes the scale-up production of UTSCs. Herein, this study reports that amorphous TiO2 layers can act as a passivating contact, which not only passivates defective rear-interfaces but also provides excellent electrical conduction, for solution-processed Cu(In,Ga)(S,Se)(2) UTSCs. The amorphous nature of TiO2 layers is found to play a key role in achieving desirable ohmic conduction over the entire area without any contact openings. Holes in absorbers easily move into amorphous TiO2 layers, even in the presence of large valence band offset (2.6 eV), proving that the defect states within these TiO2 layers act as hole conduction pathways. While control devices experience huge open-circuit voltage (V-OC) losses (-303 mV) after reduction of absorber thickness from 750 to 300 nm, devices with amorphous TiO2 layers exhibit V-OC gains (+8 mV), encouraging the realization of high-efficiency UTSCs with a simple, easily scalable, and highly reproducible process. English Wiley-VCH Verlag Amorphous TiO2 Passivating Contacts for Cu(In,Ga)(S,Se)(2) Ultrathin Solar Cells: Defect-State-Mediated Hole Conduction Article 10.1002/aenm.202203183 1 Advanced Energy Materials, v.13, no.8 Advanced Energy Materials 13 8 Y scie scopus 000907499300001 2-s2.0-85145685694 Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Physics, Applied Physics, Condensed Matter Chemistry Energy & Fuels Materials Science Physics Article ATOMIC LAYER DEPOSITION THIN-FILM SURFACE PASSIVATION BACK-CONTACT EFFICIENCY CRYSTALLIZATION ENHANCEMENT PERFORMANCE GAAS amorphous TiO2 CIGS defect states interface passivation passivating contacts solution-processing ultrathin solar cells