Mixed Sn-Pb Perovskite Materials for Stable Tandem Solar Cells
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Solution Overview
Problem
Current perovskite solar cells face challenges with the instability and degradation of Sn-based materials due to oxidation, leading to poor efficiency and thermal stability, and the complexity of synthesizing high-quality films with optimal band gap energies for device applications.
Innovation Solution
The development of mixed Sn-Pb perovskite materials with specific compositions and cation combinations, incorporating larger organic cations like ethyl ammonium (EA) and formamidinium (FA), which stabilize the crystal structure and optimize band gap energies between 1.2 to 1.6 eV, enhancing crystallinity and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Sn-based perovskite materials are used to achieve band gap energies closer to ideal values (1.23 to 1.41 eV), then light harvesting capability is improved, but the materials become more vulnerable to oxidation in air and exhibit poor thermal stability
Solution Approach 1:
The patent employs mixed cation perovskite compositions combining organic cations (methylammonium, formamidinium, ethylammonium) with inorganic cations (cesium, rubidium) and mixed metal halides (lead and tin iodides). This composite approach allows optimization of band gap energy while the specific cation combination stabilizes the crystal structure against oxidation and thermal degradation, resolving the contradiction between improved light harvesting and maintained stability.
Solution Approach 2:
The patent systematically varies the composition parameters including the ratio of organic to inorganic cations, the proportion of lead to tin, and the specific cation combinations to achieve optimal tolerance factors. By adjusting these parameters, the material achieves both the desired band gap for efficient light harvesting and enhanced structural stability to resist oxidation, directly addressing the technical contradiction.
2Reliability
If larger organic cations like ethyl ammonium and formamidinium are incorporated to stabilize crystal structure, then thermal stability and crystallinity are improved, but the complexity of synthesizing high-quality films increases
Solution Approach 1:
The patent combines multiple cations (methylammonium, formamidinium, ethylammonium, cesium, rubidium) and metal halides (lead iodide, tin iodide) into a single integrated perovskite composition system. This merging of components allows the stabilizing effects of larger organic cations to be achieved while the mixed composition facilitates simpler processing and film formation, reducing overall synthesis complexity despite the multi-component nature.
Solution Approach 2:
The patent assigns specific roles to different cations within the perovskite structure: larger organic cations (ethylammonium, formamidinium) provide thermal stability and structural framework, while the mixed metal halide composition optimizes optoelectronic properties. This local functional assignment allows each component to contribute its specific benefit while maintaining overall synthesis feasibility.
3Reliability
If mixed Pb/Sn compositions are used to optimize band gap, then efficiency and stability are improved, but increasing Sn content increases nonradiative recombination and decreases Voc
Solution Approach 1:
The patent optimizes the Sn/Pb ratio and cation composition to achieve a balanced state where sufficient tin content provides the desired band gap and stability improvement, while the specific organic-inorganic cation combination minimizes nonradiative recombination losses. By precisely controlling these compositional parameters, the patent achieves both enhanced stability and maintained voltage characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach results in highly crystalline and textured perovskite materials with improved stability and efficiency, suitable for single-junction and tandem solar cells, achieving high power conversion efficiencies and extended durability.
Implementation Method 1
Solar energy conversion is one of the most promising technologies to provide renewable energy... ideal as an absorber in photovoltaic devices
Data Source
AI summary
There is provided a perovskite material A perovskite material having the formula (I): AaA′bA″cSn(y)Pb(1-y)X3 (I) wherein A consists of a monovalent cation; A′ consists of a monovalent organic cation having an ionic radius greater than 2.53 Å; A″ consists of a monovalent inorganic cation; X comprises one or more halide anions; 0<a<1; 0<b<1; 0≤c<1; a+b+c=1; and 0<y<1. Also provided is a semiconductor device having a photoactive region comprising a perovskite material as defined herein; a semiconductor device which is a photovoltaic device; and a multijunction photovoltaic device comprising two or more sub-cells, wherein the first sub cell comprises a photovoltaic device as defined herein and a further sub-cell comprising a photoactive layer having a bandgap of between 1.5 and 1.9 eV.