Interfacial electron accumulation for efficient homo-junction perovskite solar cells. (October 2016)

• Record Type: Journal Article
• Authors: Song, Seulki; Moon, Byung Joon; Hörantner, Maximilian T.; Lim, Jongchul; Kang, Gyeongho; Park, Min; Kim, Jin Young; Snaith, Henry J.; Park, Taiho
• Is Part Of: Nano energy. Volume 28(2016:Oct.)
• Page Start: 269
• Page End: 276
• Publication Date: 2016-10
• Subjects: Perovskite solar cell -- Band bending -- Polymeric hole blocking -- Interfacial charge accumulation -- Homojunction; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2016.06.046
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Here we study perovskite solar cells based on mesoporous alumina scaffold infiltrated and capped with a perovskite absorber layer, which are devoid of a discrete n-type electron collection layer. We employ ethoxylated polyethylenimine (PEIE) to modify the interface between the perovskite absorber layer and the metallic transparent fluorine-doped SnO2 (FTO) electrode. Surprisingly, the PEIE interlayer obviates the requirement for the conventional dense-TiO2 (d-TiO2 ) compact layer (or organic fullerene layer), usually required to selectively extract electrons from the perovskite film. The self-organized PEIE interlayer produced a strong induced dipole moment at the perovskite-FTO interface, with our results indicating that electrons accumulate within the perovskite film at this interface. The resultant "n-type" contact region within the perovskite absorber layer, progressing to an intrinsic (i) region within the bulk of the perovskite layer, represents an n-i homojunction and favorably enables selective electron extraction at the FTO electrode. Resulting solar cells deliver current-voltage measured power conversion efficiencies (η) of over 15.0% and a substantial stabilized efficiency (η) of 9.1%. Although our solar cell performance remains lower than the highest reported efficiencies for perovskite solar cells employing discrete charge selective extraction layers, it indicates significant potential for "homo-junction" perovskite solar cells, once the metallic-to-perovskite contact is fully controlled. Additionally, our work identifies the potential impact of modifying the interface between the perovskite absorber and the subsequent contact materials with dipolar organic compounds, which may be applicable to optimizing contact at perovskite-semiconductor heterojunctions. Graphical abstract: Highlights: N-type less perovskite is proposed with stabilized power output efficiency. PEIE interlayer make an induced dipole at perovskite interface. Band bending of perovskite layer induces the charge accumulation. Perovskite solar cell have a permanent built-in potential which gives a stabilized maximum power output efficiency without n-type electron selective layer.