Performance Enhancement of Lead-Free Tin-Based Perovskite Solar Cells with Reducing Atmosphere-Assisted Dispersible Additive

Abstract

Sn-based halide perovskite materials have attracted tremendous attention and have been employed successfully in solar cells. However, their high conductivities resulting from the unstable divalent Sn state in the structure cause poor device performance and poor reproducibility. Herein, we used excess tin iodide (SnI 2 ) in Sn-based halide perovskite solar cells (ASnI 3 , A = Cs, methylammonium, and formamidinium tin iodide as the representative light absorbers) combined with a reducing atmosphere to stabilize the Sn 2+ state. Excess SnI 2 can disperse uniformly into the perovskite films and functions as a compensator as well as a suppressor of Sn 2+ vacancies, thereby effectively reducing the p-type conductivity. This process significantly improved the solar cell performances of all the ASnI 3 materials on mesoporous TiO 2 . Optimized CsSnI 3 devices achieved a maximum power conversion efficiency of 4.81%, which is the highest among all inorganic Pb-free perovskite solar cells to date.

Lead-free hybrid perovskites for photovoltaics

“…(a) Reprinted with permission from [71], copyright 2017 American Chemical Society; (b) Reprinted with permission from [80], copyright 2017 American Chemical Society; (c) Reprinted with permission from [118], copyright 2017 American Chemical Society.…”

Lead‐Free Solar Cells based on Tin Halide Perovskite Films with High Coverage and Improved Aggregation

“…[2][3][4][5] Theoretical calculations indicate that the perovskite crystal structure is preserved after metal cation substitution. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Rapid oxidation of Sn 2+ to Sn 4+ in ambient atmosphere dopes the perovskite layer into high conductivity,r esulting in severe electrical shunting. [2][3][4][5][6][7] Unfortunately,p ower conversion efficiencies (PCEs) obtained from Sn-based PSCs are much lower than that of their Pb counterpart.…”

“…[6] As the most promising candidate among Pb-free perovskites,t in halide perovskites show suitable band gaps and advantageous optoelectronic properties. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Rapid oxidation of Sn 2+ to Sn 4+ in ambient atmosphere dopes the perovskite layer into high conductivity,r esulting in severe electrical shunting. Though aS n-based PSC using MASnI 3 as the absorber was first demonstrated in 2014 with ar eported power conversion efficiencyo ver 5%, [8,9] theh ighest PCE achieved for aS n-based PSC to date is still below 10 %.…”

Cs1−xRbxSnI3light harvesting semiconductors for perovskite photovoltaics

“…To date it has been used as the light harvesting semiconductor in PV devices based on mesoporous TiO 2 5,6 and planar [7][8][9] device architectures, demonstrating the potential to achieve very high short circuit current density ( J sc ) of 420 mA cm À2 under one sun illumination 6 and high device fill factor (FF). 8 The primary factor limiting the power conversion efficiency of B-g CsSnI 3 based PVs is the low open-circuit voltage (V oc ): to date the highest V oc reported is 0.55 V, 8 achieved for an inverted device architecture using phenyl-C 61 -butyric acid methylester (PCBM) as the electron transport layer (ETL), which is approximately half that attainable using the lead analogue CsPbI 3 .…”