Optimizing the Back Contact of Kesterites and Perovskites: Band Edge Design and Defect Engineering in Molybdenum Chalcogenides. (29th January 2022)

• Record Type: Journal Article
• Authors: Xiang, Huiwen; Zhang, Jinping; Liang, Hanzhen; Zhu, Rui; Liu, Chengyan; Jia, Yu
• Is Part Of: Advanced sustainable systems. Volume 6:Number 4(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-29
• Subjects: back contacts -- band alignment -- defect engineering -- solar cells; Sustainable living -- Periodicals; Sustainability -- Periodicals; Green technology -- Periodicals; Periodicals; 628
• DOI: 10.1002/adsu.202100457
• Languages: English
• ISSNs: 2366-7486

Abstract

Abstract: Back contacts, as an important part of solar cell devices, play a critical role in efficient separation of carriers and reduction of interfacial recombination. Here, by analyzing interfacial band alignment, thickness and defect properties of back contacts, a design principle for back contacts is proposed to properly accommodate the interrelated factors of short‐circuit current ( J sc ), open‐circuit voltage ( V oc ), series resistance ( R s ), and nonradiative recombination centers (NRCs) at the same time. A preferred back contact should have (i) a high valance band maximum (VBM) and (ii) a low Fermi level relative to absorber to drive hole extraction and block electron leakage, (iii) a thin design under the premise of p + ‐type characteristic to effectively reduce R s, which also ensures a wide depletion region on the absorber side to promote hole collection, and (iv) no additional deep‐level defects as interfacial NRCs. Taking molybdenum chalcogenide as example, p + ‐type MoSe2 /MoS2 realized by group VB element doping satisfies the design principles and is promising as an excellent back contact for kesterite/perovskite solar cells. This study gives theoretical guidance for designing an ideal back contact and shows how to improve the photovoltaic performance of solar cells by interfacial optimization. Abstract : A desirable back contact for p‐type absorbers in solar cells should have a higher valence band maximum and a lower Fermi level relative to the absorber, to facilitate the extraction of photogenerated holes, prevent the leakage of electrons, and reduce the series resistance, resulting in high‐efficiency solar cells.