Chalcogen Double Perovskites for Lead-Free Optoelectronics
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Solution Overview
Problem
Current perovskite materials for optoelectronic applications face challenges due to the use of lead, which is toxic and environmentally unfriendly, and the need for materials with direct band gaps less than 3 eV for efficient photovoltaic and electroluminescent performance.
Innovation Solution
Development of chalcogen double perovskites, such as Ba2AgIO6, which have a direct band gap in the visible region, are synthesized using a low-temperature solution processing route, replacing lead with non-toxic elements like indium and antimony, and optimizing the electronic valency of cations at the B sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lead-halide perovskites are used to achieve high power conversion efficiency, then photovoltaic performance is improved, but environmental toxicity worsens
Solution Approach 1:
The patent changes the chemical composition parameters by replacing lead (Pb) with non-toxic elements such as bismuth (Bi), antimony (Sb), and thallium (Tl) in the perovskite structure. This substitution maintains the optoelectronic properties while eliminating environmental toxicity, directly resolving the contradiction between efficiency and environmental harm
Solution Approach 2:
The patent employs composite material design by creating double perovskite structures (A2BB'X6) that combine multiple elements with complementary properties. The B-site cations (Bi3+, Sb3+, Tl3+) are paired with monovalent cations (Ag+, Cu+, In+) to form composite structures that achieve both high efficiency and environmental friendliness simultaneously
2Use of energy by moving object
If Cs2BiAgBr6 is used to achieve low band gap of 1.9 eV, then light absorption is improved, but band gap type worsens (indirect gap)
Solution Approach 1:
The patent systematically varies the composition parameters at the B-site by substituting different combinations of Bi3+, Sb3+, Tl3+ with Ag+, Cu+, In+ to tune the electronic structure. This compositional tuning transforms the indirect band gap of Cs2BiAgBr6 into a direct band gap structure while maintaining low energy values suitable for optoelectronic applications
Solution Approach 2:
The patent applies local quality optimization by specifically designing the B-site cation configuration to achieve direct band gap characteristics. The ordered arrangement of B and B' cations in the double perovskite structure creates favorable local electronic environments that enable direct transitions, resolving the band gap type issue while preserving low energy
3Reliability
If Cs2AgInCl6 is used to achieve direct band gap, then optoelectronic performance is improved, but band gap value worsens (relatively large at 3.3 eV)
Solution Approach 1:
The patent changes the compositional parameters by substituting Cl- anions with Br- or I- anions, and adjusting the B-site cation ratios. These parameter changes reduce the band gap energy from 3.3 eV to values below 3 eV while preserving the direct band gap characteristic, achieving both reliability and energy efficiency
4Object-affected harmful factors
If non-toxic elements (In, Sb, Bi) are used to replace lead, then environmental friendliness is improved, but synthesis complexity worsens
Solution Approach 1:
The patent applies preliminary action by pre-mixing the non-toxic metal salts (In, Sb, Bi, Ag, Cu, Tl) with organic ligands and solvents to form homogeneous precursor solutions before deposition. This preliminary preparation simplifies the subsequent synthesis process, eliminating the need for complex multi-step procedures while achieving high-quality perovskite films with non-toxic compositions
Data Source
Figure 1a~1b
Figure 2
Figure 3a
AI summary
The invention relates to an optoelectronic material comprising a compound, wherein the compound comprises: (i) one or more cations, A; (ii) one or more first B cations, Bn+; (iii) one or more second B cations, Bm+; and (iv) one or more chalcogen anions, X; wherein the one or more first B cations, Bn+ are different from the one or more second B cations, Bm+; n represents the oxidation state of the first B cation and is a positive integer of from 1 to 7 inclusive; m represents the oxidation state of the second B cation and is a positive integer of from 1 to 7 inclusive; and n + m is equal to 8.