Overcoming the Open-Circuit Voltage Losses in Narrow Bandgap Perovskites for All-Perovskite Tandem Solar Cells
Yekitwork Abebe Temitmie, Muhammad Irfan Haider, Daniele T. Cuzzupè, Lucia V. Mercaldo, Stefan Kraner, Paola Delli Veneri, Amare Benor, Azhar Fakharuddin, Lukas Schmidt‐Mende
Abstract
High Resolution Image Download MS PowerPoint Slide Narrow-bandgap (NBG) perovskite solar cells based on tin–lead mixed perovskite absorbers suffer from significant open-circuit voltage ( V OC ) losses due primarily to a high defect density and charge carrier recombination at the device interfaces. In this study, the V OC losses in NBG perovskite single junction cells ( E g = 1.21 eV) are addressed. The optimized NBG subcell is then used to fabricate highly efficient all-perovskite tandem solar cells (TSCs). The improvement in the V OC is achieved via the addition of a thin poly(triarylamine) interlayer between the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)-based hole transport layer (HTL) and the NBG perovskite. The optimal bilayer HTL results in a champion power conversion efficiency (PCE) of 20.3%, compared to 17.8% of the PEDOT:PSS-based control device. The V OC improvement of the single-junction NBG cell is also successfully transferred to all-perovskite TSC, resulting in a high V OC of 2.00 V and a PCE of 25.1%.