Different structural evolutions of inorganic perovskite CsGeI₃

Abstract

Distinguished from CsSnI3 perovskite systems, the most stable non-centrosymmetric trigonal structure (space group of R3m) of CsGeI3 perovskite system is found in our calculations. We systematically study the differences between...

Remarkable Stability and Optoelectronic Properties of an All-Inorganic CsSn0.5Ge0.5I3 Perovskite Solar Cell

“…The DOS of Ge I /Sn I defects are calculated and the deep energy levels in the forbidden band are clearly found in both P 1-CsSn 0.5 Ge 0.5 I 3 and R 3 m -CsSn 0.5 Ge 0.5 I 3 systems, which will introduce the electron–hole nonradiative recombination and inhibition the efficiency (Figure ). It can be seen in Figures a and c that the Sn I and Ge I antisite defects of the CsSn 0.5 Ge 0.5 I 3 - P 1 structure are both obvious deep level defects, which are consistent with the studies of other structures. , In order to further explore the nature of Ge I /Sn I defect, the band structure of the defect systems is also calculated (Figure S2). Both of them are clearly deep in the forbidden band close to the CBM, in agreement with our DOS calculations.…”

“…It can be seen in Figures 4a and c that the Sn I and Ge I antisite defects of the CsSn 0.5 Ge 0.5 I 3 -P1 structure are both obvious deep level defects, which are consistent with the studies of other structures. 17,43 In order to further explore the nature of Ge I / Sn I defect, the band structure of the defect systems is also calculated (Figure S2). Both of them are clearly deep in the forbidden band close to the CBM, in agreement with our DOS calculations.…”

“…However, the toxicity caused by lead has always pushed people to seek lead-free perovskites considering environment-friendly applications. Many researchers investigate a lot of low-toxic or nontoxic inorganic perovskite materials, , so Ca­(II), Bi­(III), Sr­(II), Sn­(II), and Ge­(II) cations were used to replace Pb cations. − Among them, Sn-based perovskites have the potentially ideal electronic and optical properties that are even better than those of Pb-based perovskite due to its band gap close to the optimal one (≈1.3 eV), strong light absorption, and good carrier mobility. − In addition, the controllability of Sn content in CsSnI 3 enables it to be used not only as a light-absorbing layer but also as a hole transport material for lead-free perovskite solar cells. ,− However, the thermal instability and thermodynamically favorable antisite defect Sn I are the main reasons limiting the PCE of inorganic Sn-based perovskites. − Compared with inorganic Pb/Sn-based perovskites, Ge-based perovskites show different structural and electronic properties, especially its defect physics: the antisite defects will not dominate during fabrication. , Under Ge-rich/I-rich conditions, the formation energies of Ge and I vacancies are relatively low and CsGeI 3 is a p-type direct band gap semiconductor . But unfortunately, the I vacancy in CsGeI 3 is a deep electron trap under I-poor conditions, which obviously limits electron migration, thereby affecting the V OC of PSC. , In order to improve the photovoltaic performance of inorganic perovskite devices, researchers performed Sn and Ge hybridization to obtain a CsSn 0.5 Ge 0.5 I 3 perovskite, a promising lead-free light-absorbing material (LAM).…”

Ferroelectric CsGeI3 Single Crystals with a Perovskite Structure Grown from Aqueous Solution

“…The thermal analysis results in Figure d are similar to what has been reported for powder CGI crystals. Phase transformation is found to happen from the rhombohedral ( R 3 m ) to cubic ( Pm 3̅ m ) phase , at 275 °C, and the melting point is verified at 430 °C. Due to the decomposition of GeI 2 from part of the CGI at 450 °C, we have observed a stronger peak (450 °C) after 430 °C.…”

Pb-free halide perovskites for solar cells, light-emitting diodes, and photocatalysts

“…158 Indeed, their bandgaps (R3m space group) are linearly increasing with respect to the concentration of Ge. 159 For instance, the CsSn 0.5 Ge 0.5 I 3 has a bandgap (1.50 eV) in between CsSnI 3 (1.31 eV) and CsGeI 3 (1.63 eV) and allows photo-absorption across the visible light region. 32 As a result, a PCE of 7.11% is obtained for CsSn 0.5 Ge 0.5 I 3 in comparison to the 3.72% attained without forming a native-oxide layer and the 1.7% of the pure CsSnI 3 .…”