Highly Efficient 17.6% Tin-Lead Mixed Perovskite Solar Cells Realized through Spike Structure.

Kapil, Gaurav; Ripolles, Teresa S; Hamada, Kengo; Ogomi, Yuhei; Bessho, Takeru; Kinoshita, Takumi; Chantana, Jakapan; Yoshino, Kenji et al. · Nano Lett · 2018

basic_science · Level V

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Abstract

Frequently observed high V<sub>oc</sub> loss in tin-lead mixed perovskite solar cells is considered to be one of the serious bottle-necks in spite of the high attainable Jsc due to wide wavelength photon harvesting. An amicable solution to minimize the V<sub>oc</sub> loss up to 0.50 V has been demonstrated by introducing an n-type interface with spike structure between the absorber and electron transport layer inspired by highly efficient Cu(In,Ga)Se<sub>2</sub> solar cells. Introduction of a conduction band offset of ∼0.15 eV with a thin phenyl-C61-butyric acid methyl ester layer (∼25 nm) on the top of perovskite absorber resulted into improved V<sub>oc</sub> of 0.75 V leading to best power conversion efficiency of 17.6%. This enhancement is attributed to the facile charge flow at the interface owing to the reduction of interfacial traps and carrier recombination with spike structure as evidenced by time-resolved photoluminescence, nanosecond transient absorption, and electrochemical impedance spectroscopy measurements.