Lead Free Perovskites

TL;DR

This paper explores lead-free perovskite solar cells, focusing on tuning their band gaps via B-site cation replacement to improve stability and reduce toxicity, with experimental findings on optical band gaps of various compositions.

Contribution

It provides new experimental data on the optical band gaps of tin, copper, and mixed perovskites, challenging existing theoretical predictions and advancing lead-free solar cell research.

Findings

Tin and lead perovskite band gaps re-established

Copper-based perovskite disagrees with DFT calculations

Mixed tin and copper perovskite results contradict predictions

Abstract

One of the most viable renewable energies is solar power because of its versatility, reliability, and abundance. In the market, a majority of the solar panels are made from silicon wafers. These solar panels have an efficiency of 26.4 percent and can last more than 25 years. The perovskite solar cell is a relatively new type of solar technology that has a similar maximum efficiency and much cheaper costs, the only downside is that it is less stable and the most efficient type uses lead. The name perovskite refers to the crystal structure with an ABX3 formula of the perovskite layer of the cell. All materials possess a property called a band gap. The smaller the band gap the more conductive the material, but this does not necessarily mean that the smaller the band gap the better the solar cell. The Shockley-Queisser limit provides the optimal band gap in terms of efficiency for a single junction solar cell which is 1.34 eV for single junction cells. This research focuses on tuning the band gap of lead-free perovskites through B-site cation replacement. Through this investigation, the optical band gaps of tin and lead perovskites were re-established. However, the copper-based perovskite disagrees with existing DFT calculations. Additionally, the mixed tin and copper perovskite in this experiment contradicts the intuitive prediction.