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Strain relaxation and light management in tin-lead perovskite solar cells to achieve high efficiencies Gaurav Kapil, Takeru Bessho, Chi Huey Ng, Kengo Hamada, Manish Pandey, Muhammad Akmal Kamarudin, Daisuke Hirotani, Takumi Kinoshita, Takashi Minemoto, Qing Shen, Taro Toyoda, Takurou N Murakami, Hiroshi Segawa, and Shuzi Hayase ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.9b01237 • Publication Date (Web): 17 Jul 2019 Downloaded from pubs.acs.org on July 18, 2019
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ACS Energy Letters
Strain relaxation and light management in tin-lead perovskite solar cells to achieve high efficiencies Gaurav Kapil1,2*, Takeru Bessho1, Chi Huey Ng2, Kengo Hamada2, Manish Pandey2, Muhammad Akmal Kamarudin2, Daisuke Hirotani2, Takumi Kinoshita1, Takashi Minemoto3, Qing Shen4, Taro Toyoda4, Takurou N. Murakami5, Hiroshi Segawa1, Shuzi Hayase2* 1The
University of Tokyo, Research center for Advanced Science and Technology, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8904, Japan. 2 Kyushu Institute of Technology, Graduate School of Life Science and Systems Engineering,
2-4 Hibikino, Wakamatsu-ku, Kitakyushu, 808-0196 Japan. 3Ritsumeikan
University, Department of Electrical and Electronic Engineering, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan 4University
of Electro Communication, Graduate school of Informatics and Engineering, 15-1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan 5The
National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan Correspondence Author:
[email protected],
[email protected] Supporting Information: The Supporting Information is available free of charge on the ACS publication website at DOI: XXXX. Description of the solar cell fabrication, characterization methods, WilliamsonHall plot, Tauc plot, Urbach Energy calculation, PYS plot, JV curves of comparsion between devices fabricated on FTO and ITO, Lattice parameters of different perovskites prepared in the study, Table of fitted TRPL data. Abstract: Tin-lead (Sn-Pb) based perovskite solar cells (PSCs) still exhibit inferior power conversion efficiency (PCE) than their pure Pb counterparts because of high voltage loss (VL), and high photocurrent loss in the infrared region. This study explores that a small amount of Cesium
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ion (Cs+) incorporation in the lattice of Sn-Pb perovskite can reduce the relative lattice strain, which in turn decreased the VL less than 0.50 V. Moreover, surface and bulk trap densities also seem to be reduced by Cs+ addition as concluded by thermally stimulated current measurements and increased carrier lifetime by photoluminescence study. It was discovered that a small amount of Cs+ was lowering the Urbach energy, which can be used as a signature to optimize the optoelectronic and the photovoltaic properties of multi-cation perovskite materials. This study further demonstrates that a high external quantum efficiency (~80% at 900 nm) can be obtained with fluorine doped tin oxide (FTO) glass rather than frequently used indium tin oxide (ITO) glass. The strategies employed in the work improved opencircuit voltage to 0.81 V, photocurrent density of ˃30 mA/cm2 and a PCE of ˃20% using a band gap of 1.27 eV.
The rapid rise in power conversion efficiencies (PCE) of perovskite solar cells (PSCs) in last decade from 3.9% to 24.2%1-3 have boosted the worldwide interest among solar cell community to raise it further near to the Shockley Queisser limit4, 5. It has been recognized that organic-inorganic hybrid perovskite (OIHP) absorbers display excellent optoelectronic properties owing to the high absorption coefficient, ambipolar charge transport, long lifetime and diffusion length of photogenerated carriers6. These properties can be intrinsically changed by employing different A (monovalent cation), B (bivalent cation) and X (halide anion) combinations in a typical ABX3 perovskite structure7. At the beginning of PSC research, the A position was entirely occupied by an organic cation, methylammonium
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ACS Energy Letters
(MA+)2. However, later it was discovered that some other cations such as formamidinium (FA+), cesium (Cs+), rubidium (Rb+) etc., can be placed solely or in combination at A position provided that the effective tolerance factor [teffective = (reffective + rX-)/ 21/2(rB2+ + rI-), reffective = xrA+ + (1-x)rB+ ; r are the respective ionic radii] lies in between 0.8< teffective
