Theoretical impacts of single band gap grading of perovskite and valence band offset of perovskite/hole transport layer interface on its solar cell performances. (1st January 2022)

• Record Type: Journal Article
• Authors: Kawano, Yu; Chantana, Jakapan; Negami, Takayuki; Nishimura, Takahito; Mavlonov, Abdurashid; Minemoto, Takashi
• Is Part Of: Solar energy. Volume 231(2022)
• Page Start: 684
• Page End: 693
• Publication Date: 2022-01-01
• Subjects: Solar cell -- Perovskite -- Device simulation -- Band gap grading -- Valence band offset; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2021.11.072
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Sn and Br composition in CH3 NH3 (Sn x Pb1− x )(I1− y Br y )3 perovskites affects their Eg . Highest PCE is obtained under optimized Eg grading (1.47/1.33 eV at front/back). L n, p of 2.5 μm and perovskite thickness of 0.75 μm yields the highest PCE of 26.0%. Optimized Eg grading and PCE were similar when L n, p was increased from 5 to 100 μm. Optimized VBO ranges from −0.1 to +0.2 eV regardless of Eg-grading to improve PCE. Abstract: Single bandgap (Eg )-grading in CH3 NH3 (Sn x Pb1− x )(I1− y Br y )3 perovskites and valence band offset (VBO) of a perovskite/hole transport layer (HTL) interface of perovskite solar cells (PSCs) are theoretically scrutinized. Eg values at front and back is defined as Eg values of perovskite at light incident side and back side, respectively, which are changed from 1.10 eV to 1.80 eV based on Sn and Br compositions for different Eg-grading. It is disclosed that optimized single Eg-grading (1.47 / 1.33 eV at front/back) results in enhancement of cell performances because of effective utilization of broader solar spectrum and formation of electric field in direction of promoting charge separation. Furthermore, optimized carrier diffusion length of 2.5 μm and perovskite thickness of 0.75 μm yields the highest power conversion efficiency of 26.0%. CH3 NH3 (Sn0.07 Pb0.93 )I3 at front for front Eg of 1.47 eV and CH3 NH3 (Sn0.38 Pb0.62 )I3 at back for back Eg of 1.33 eV are thus suggested for optimized single Eg-grading. Moreover, optimized VBO is in a range from − 0.1 eV to + 0.2 eV regardless of Eg-grading to improve cell performances. The results indicated that PEDOT:PSS, Spiro-OMeTAD, and PTAA as HTL are ultimately suitable for CH3 NH3 (Sn x Pb1− x )I3 based PSCs, whereas NiOx and CuOx as HTL is appropriate for CH3 NH3 (Sn x Pb1− x )I3 and CH3 NH3 Pb(I1− y Br y )3 based PSCs.