Improved Stability and Performance in Highly Efficient Lead‐Free Hybrid Perovskite Solar Cells

PI: Tonio Buonassisi, Department of Mechanical Engineering, MIT
PI: Pavel Troshin, Center for Electrochemical Energy Storage, SKoltech

The hybrid lead iodide based perovskites APbI3 (A – methylammonium, formamidium) have recently demonstrated outstanding electronic properties such as very low exciton binding energy (~2 meV), high electron‐hole diffusion lengths (>150 mm) and excellent charge carrier mobility (>100 cm2V‐1s‐1). The solution‐processed thin‐film solar cells based on these materials have shown certified efficiencies exceeding 20%, thus coming close to the state‐of‐the‐art silicon devices. Unfortunately, practical use of these exciting materials is hardly possible due to their extremely low stability: they undergo facile thermal, electrochemical and photochemical decomposition. In addition, use of toxic lead salts in solar cells would make it difficult for this product to enter the market. In this project we plan to address the problem of intrinsic instability of the lead iodide based perovskites. We propose to develop a novel generation of lead‐free hybrid semiconductor materials, which would combine advanced optoelectronic properties with the high operational stability. To solve the problem, we will focus on the chemical design and engineering of novel bulk perovskite‐inspired materials ABX3, A3B2X9, ABX2, A2BX4, and A4B3X10 using different organic cations (A), divalent metals (B) and anion species (X). We will systematically investigate photochemical, electrochemical and thermal degradation of the designed materials to reveal fundamental correlations between their intrinsic stability and chemical compositions/structures. Some chemical pathways of the material degradation will be determined. Guidelines for designing novel highly stable materials will be formulated. Successful implementation of the project will stimulate the development of the disruptive third‐generation photovoltaic technology, which will contribute significantly to the production of the renewable energy in the nearest future.

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