Researchers from India's Chiktara University have reported improved stability and performance of organic-inorganic perovskite solar cells by applying a strategy called bandgap grading.
The method is based on enabling the cell perovskite absorber to collect a wider range of light photons by modifying its thickness and characteristics. The team explains that its recent study demonstrates the effectiveness of both linear and parabolic bandgap grading strategies in optimizing light absorption and boosting performance, showing its potential.
The scientists used the SCAPS-1D solar cell capacitance software, developed by the University of Ghent, to simulate the novel cell configuration. They cell relies on a lead-free, tin-based perovskite material known as CsSnI3-xBrx. The incorporation of bandgap tailoring is said to lead to modulated bandgap/affinity along the depth of the absorber layer, which uplifts the efficiency of the solar cell, as the scientists explained.
The cell was initially designed to have a substrate made of fluorine-doped tin oxide (FTO), an electron transport layer (ETL) based on ceric oxide (CeO2), the perovskite absorber, a hole transport layer (HTL) made with copper, iron and tin (Cu2FeSnS4), and a gold (Au) metal contact.
For both the ETL and the HTL the thickness was assumed to be 100 nm, while for the absorber the researchers considered a thickness ranging from 50 nm to 500 MW, with variable bandgap energy comprised between 1.25 eV and 1.78 eV.
Tested under standard illumination conditions, the proposed solar cell configuration achieved a power conversion efficiency of 23.61% with the parabolic grading approach and 21.68% with linear grading. The simulations also showed that by replacing the utilized ETL and HTL materials with tin oxide (SnO2) and PEDOT:PSS, respectively, the efficiency of the cell may also exceed 24%.
