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. •Three effective techniques are used to enhance the performance of four-terminal perovskite/c-Si tandem solar cell.•The strategies focus on enhancement of the transmissivity of the rear electrode of the top cell.•Passivation of defects in CH3NH3PbI3 devices by oxygen annealing.•Maximization of the light harvesting power of the tandem devices.•An overall PCE of 22.4% in average can be achieved for an optimized tandem device.