Cesium-Trifluoroacetate Doped MA/FA-Based Perovskite Solar Cells with Inverted Planar Structure
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https://doi.org/10.1007/s11664-020-08492-1 2020 The Minerals, Metals & Materials Society
Cesium-Trifluoroacetate Doped MA/FA-Based Perovskite Solar Cells with Inverted Planar Structure CHUNXIA WU,1,2 LIANG ZHU,1 YUNFANG ZHANG,2 and JUN DAI2,3 1.—College of Materials Science and Engineering, Jiangsu University, Zhenjiang 212003, China. 2.—College of Science, Jiangsu University of Science and Technology, Zhenjiang 212003, China. 3.—e-mail: [email protected]
Triple cation perovskites are of particular interest among halide perovskites due to their impressive photovoltaic performance. In this paper, we introduce cesium trifluoroacetate (CsTFA) into methylammonium/formamidinium (MA/ FA) perovskite to prepare a triple cation Cs/MA/FA perovskite solar cell with inverted planar structure. The effects of CsTFA concentration and spinning speed of the perovskite layer on the morphology of perovskite film and performance of the perovskite solar cell are studied. We find that the power conversion efficiency can be 10.55% when the spinning speed is 6000 rpm and CsTFA content is 5%. When, ethylammonium chlorine (MACl) is then employed to passivate the Cs/MA/FA-based perovskite thin film surface, the power conversion efficiency (PCE) is further improved to 12.19%. The results indicate that CsTFA can be a potential source of Cs ions for triple cation Cs/ MA/FA perovskite solar cells. Key words: Perovskite solar cells, CsTFA, methylammonium chlorine
INTRODUCTION In recent years, hybrid organic–inorganic lead halide perovskite solar cells (PSCs) have shown exciting developments, with power conversion efficiency (PCE) increasing from 3.8% in 2009 to the current 25.2%.1–10 These gains can be attributed to their excellent optoelectronic properties, such as tunable bandgap, ambipolar charge transport, high power conversion efficiency, long carrier diffusion length, small exciton binding energy and low trap densities.11–13 Typically, perovskite solar cells present an ABX3 structure, where A is an organic cation such as (methylammonium (MA) CH3NH3+; formamidinium (FA) CH3(NH2)2+)+), or inorganic cation Cs+, B is the divalent metal Pb2+ or Sn2+and X is the halide anion (I , Cl , Br or mixture halide).14,15 MAPbI3 and FAPbI3 are unstable when they are exposed to air and high moisture environments, which leads to rapid degradation in PSC
(Received July 14, 2020; accepted September 15, 2020) Chunxia Wu and Liang Zhu have contribute equally to this work.
performance.16,17 Recently, triple cation Cs/MA/FA perovskites, which offer narrower bandgap, better humidity and thermal stability, have been shown to result in stabilized PCEs exceeding 21% for perovskite solar cells with normal architecture.18–23 Although the pervoskite solar cell normal architecture has higher PCE, the inverted structure is much more easily fabricated. In addition, a small amount of Cs+ doping in the FAPbI3 perovskite can effectively inhibit non-perovskite d-phase, which is beneficial in growing large grain, defect-free perovskite thin films.24,25 CsI is widely acce
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