Mixed Sn–Ge Perovskite for Enhanced Perovskite Solar Cell Performance in Air

Abstract

Lead-based perovskite solar cells have gained ground in recent years, showing efficiency as high as 20%, which is on par with that of silicon solar cells. However, the toxicity of lead makes it a nonideal candidate for use in solar cells. Alternatively, tin-based perovskites have been proposed because of their nontoxic nature and abundance. Unfortunately, these solar cells suffer from low efficiency and stability. Here, we propose a new type of perovskite material based on mixed tin and germanium. The material showed a band gap around 1.4-1.5 eV as measured from photoacoustic spectroscopy, which is ideal from the perspective of solar cells. In a solar cell device with inverted planar structure, pure tin perovskite solar cell showed a moderate efficiency of 3.31%. With 5% doping of germanium into the perovskite, the efficiency improved up to 4.48% (6.90% after 72 h) when measured in air without encapsulation.

Lead‐Free Tin‐Based Perovskite Solar Cells: Strategies Toward High Performance

“…Despite the poor performance of Ge‐based PSCs, it was predicted theoretically that the substitution of Sn 2+ with Ge 2+ displays stability over the initial pure counterparts, which has been proved by experimental reports. Ito et al and Ng et al used the same optimized composition FA 0.75 MA 0.25 Sn 0.95 Ge 0.05 I 3 to fabricate inverted PSCs and obtained champion PCEs of 6.90% and 7.9%, respectively. Both of the devices exhibited significantly improved stability in ambient air and the latter maintained 90% of its original efficiency under constant illumination for 600 min.…”

MACl‐Assisted Ge Doping of Pb‐Hybrid Perovskite: A Universal Route to Stabilize High Performance Perovskite Solar Cells

“…Interestingly, addition of germanium (Ge) at B site cation has been recently reported to be effective for the improvement of both stability and PCE of all‐inorganic perovskite solar cells. Here, unlike oxidation of Sn, oxidization of Ge, forming germanium oxide, seemed to have a positive effect in terms of defects passivation . Despite such advantage of Ge, the strategy has not been applied to organic–inorganic hybrid perovskites.…”

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 %.…”