Yb-Doped Double Perovskite Thin Films for Solar Spectral Downconversion
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Solution Overview
Problem
Existing solar cells face inefficiencies due to UV penetration and thermal losses, and current Yb-doped materials like CsPbX3 suffer from toxicity and reduced performance at high photon fluence, limiting their ability to enhance solar cell efficiency and lifetime.
Innovation Solution
Development of Yb-doped double perovskite thin films with specific compositions such as M2AYbxB(1-x)X6, where M represents Cs or Rb, A represents Ag or Cu, B represents Bi, In, Sb, or Ga, and X represents F, Cl, Br, or I, which are deposited and annealed to achieve high photoluminescence quantum yields, converting UV and blue photons to NIR photons, thereby enhancing solar cell efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Yb-doped CsPbX3 materials are used for downconversion, then photoluminescence quantum yield can exceed 100% via quantum cutting, but the materials are toxic and performance decreases at high photon fluence
Solution Approach 1:
The patent extracts and removes the toxic lead element from the perovskite structure, replacing it with non-toxic alternatives (bismuth, antimony, or gallium) while maintaining the double perovskite structure M2ABX6. This extraction of the harmful component allows the material to achieve high photoluminescence quantum yield through quantum cutting without the detrimental effects of lead toxicity and high-photon-fluence degradation.
Solution Approach 2:
The patent employs composite material design by creating double perovskites with specific compositional ratios of non-toxic elements (Bi, Sb, or Ga combined with other cations) to achieve both high quantum cutting efficiency and stability under high photon fluence. The composite structure M2AYbxB(1-x)B'(1-x)X6 allows optimization of both optical performance and chemical stability.
2Productivity
If conventional Yb-doped perovskites are used, then spectral shifting can be achieved, but photoluminescence quantum yield remains below the minimum required to increase solar cell efficiencies
Solution Approach 1:
The patent systematically changes key parameters including Yb doping concentration (x = 0.01-0.20), halide composition ratios (Cl, Br, I), and double perovskite structure composition to optimize photoluminescence quantum yield. By adjusting these parameters, the material achieves quantum cutting efficiency exceeding the minimum threshold required for solar cell efficiency enhancement while maintaining structural stability.
3Loss of energy
If UV and blue photons are absorbed by solar cells, then direct energy conversion occurs, but thermal losses and electron-hole pair recombination increase
Solution Approach 1:
The patent introduces a downconversion layer containing Yb-doped double perovskite as an intermediary between the solar cell and the UV/blue spectrum. This intermediary absorbs high-energy photons and converts them to lower-energy NIR photons through quantum cutting, which then penetrate deeper into the solar cell with reduced thermal losses and minimized recombination, thereby improving overall efficiency.
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 Yb-doped double perovskite films achieve photoluminescence quantum yields of at least 45%, increasing the efficiency of silicon and CIGS solar cells by up to 0.3% and improving their lifetimes by reducing UV penetration and thermal losses.
Implementation Method 1
Shifting the UV and blue spectrum to NIR reduces thermal losses and the recombination of electron-hole pairs generated from shallow light absorption near interfaces. Ytterbium (Yb) is a well-known luminophore for solar spectral shifting because the Yb3+ emission via 2F5/2→2F7/2 electronic transition at 1.24 eV is close to the bandgap of silicon
Implementation Method 2
If the host bandgap is greater than twice the Yb3+ 2F5/2→2F7/2 electronic transition, the energy transfer from the host to Yb3+ can be via quantum cutting, a process wherein one UV-blue photon is converted to two NIR photons. In this case, PLQY can be >100% with a maximum of 200%
Data Source
AI summary
Described is a thin film comprising a Yb-doped double perovskite, wherein the double perovskite has the formula M2AYbxB(1-x)X6; wherein each occurrence of M independently represents Cs or Rb; A represents Ag or Cu; B represents Bi, In, Sb, or Ga; x has a value between 0.01 and 0.20; and each X independently represents F, Cl, Br, or I. Also described is a method of making the thin films. The thin film may be useful in photovoltaic devices.