All‐Inorganic CsPb_1−xGe_xI₂Br Perovskite with Enhanced Phase Stability and Photovoltaic Performance

Abstract

Compared with organic‐inorganic perovskites, all‐inorganic cesium‐based perovskites without volatile organic compounds have gained extensive interests because of the high thermal stability. However, they have a problem on phase transition from cubic phase (active for photo‐electric conversion) to orthorhombic phase (inactive for photo‐electric conversion) at room temperature, which has hindered further progress. Herein, novel inorganic CsPb1−xGexI2Br perovskites were prepared in humid ambient atmosphere without a glovebox. The phase stability of the all‐inorganic perovskite was effectively enhanced after germanium addition. In addition, the highest power conversion efficiency of 10.8 % with high open‐circuit voltage (VOC) of 1.27 V in a planar solar cell based on CsPb0.8Ge0.2I2Br perovskite was achieved. Furthermore, the highest VOC up to 1.34 V was obtained by CsPb0.7Ge0.3I2Br perovskite, which is a remarkable record in the field of all‐inorganic perovskite solar cells. More importantly, all the photovoltaic parameters of CsPb0.8Ge0.2I2Br perovskite solar cells showed nearly no decay after 7 h measurement in 50–60 % relative humidity without encapsulation.

Interstitial doping of K and Mn induced structural distortion and electronic properties changes in all‐inorganic CsPbI2Br perovskite

“…In the mixed-halide CsPbI 3-x Br x perovskites, it was found that CsPbI 2 Br has not only a suitable bandgap of 1.92 eV but also a considerably high ambient stability, implying that the composition engineering would be an effective strategy for stabilizing crystal [18]. Moreover, there have been many metal cations with smaller ionic radii including K + , Mn 2+ , Co 2+ , Zn 2+ , Ge 2+ , Sr 2+ , Eu 2+ and Ba 2+ introduced into the interstitial or substitutional sites of cesium lead halide perovskites, with various purposes like enhancing phase stability, manipulating crystallization process, passivating defects, optimizing energy band, suppressing ion migration, improving optoelectronic properties, etc [19][20][21][22][23][24][25][26]. It is worth noting that some experimental results showed that the alkali metal ion K + prefers to substitute for Cs + , while some other researches proved from both experimental and theoretical perspectives that K + ions are energetically to occupy the interstitial sites of perovskite lattices such as MAPbI 3 , FAMAPbI 2 Br, (FAPbI 3 ) 0.875 (CsPbBr 3 ) 0.125 and so on [27][28][29].…”

Metal cation s lone-pairs increase octahedral tilting instabilities in halide perovskites

“…2 This motivates recent efforts to develop new photovoltaic cells that are based on nontoxic perovskite halides, where Pb 2+ is replaced with Sn 2+ and/or Ge 2+ . [3][4][5][6][7] From a fundamental standpoint, the fascinating optoelectronic properties of HPs are closely related to their highly anharmonic thermal motions that lead to local, polar fluctuations and thus, localization of charge carriers. [8][9][10][11]75 The perovskite crystal (with stoichiometry AMX 3 ) consists of a three-dimensional network of corner-sharing MX 6 octahedra, with A-site cations occupying the cuboctahedral voids.…”

One‐Source Strategy Boosting Dopant‐Free Hole Transporting Layers for Highly Efficient and Stable CsPbI2Br Perovskite Solar Cells

“…[ 21 ] Poly(3‐hexylthiophene) (P3HT), which is inexpensive and exhibits excellent hole mobility, has been used as an alternative dopant‐free hole transport material (HTM). [ 22,23 ] The unencapsulated P3HT‐based devices with a CsPbI 2 Br active layer maintained ≈95% of their initial PCE after 1300 h of storage in ambient conditions. [ 24 ] Tian et al.…”