Strategies for high performance perovskite/crystalline silicon four-terminal tandem solar cells

In this work, we report systematic studies on improving the optical and electrical properties of four-terminal perovskite/c-Si tandem solar cells. Light harvesting power of the device is significantly enhanced due to the complementary absorption spectra of the perovskite and c-Si absorber materials. To obtain high power conversion efficiency (PCE) for the device, careful engineering of optoelectronic properties of the devices are accomplished through: 1. Oxygen annealing treatment for reducing defect density of perovskite materials; 2. Optical engineering of the transparent electrode (MoO₃/Au/MoO₃) to obtain high transmission at long wavelengths for the tandem solar cell applications; and 3. Enhancement of light harvesting power achieved by using the novel biomimicking elastomeric petals as the light trapping layer. The individual perovskite solar cell (PSC) with MoO₃/Au/MoO₃ electrode with or without light trapping layer yields an average PCE of 16.6% and 16.0% respectively. By combining c-Si bottom cell with perovskite top cell mechanically, an overall PCE of 22.4% is achieved for the averaged value, which is a promising result for future development of perovskite based tandem solar cells.