Quantum Dot Bridges Enabling Highly Efficient Carbon-Based Hole Transport Material-Free Perovskite Solar Cells

The realization of improved charge transport with suppressed recombination at the interface of perovskite and carbon electrode is the main key for remarkably increasing the power conversion efficiency of carbon-based hole transport material (HTM)-free perovskite solar cells (PSCs). Herein, a strategy that builds a perovskite quantum dot (PQD) interlayer is demonstrated, for the first time, to bridge the perovskite absorber and carbon electrode for solving the interface issue in HTM-free PSCs. It is found that the introduced PQD interlayer concurrently functions as a morphology changer, a defect passivator, and a photogenerated hole extractor. Compared with the pristine perovskite film, the PQD-modified perovskite absorber shows increased contact area and high compatibility with carbon electrode, prolonged carrier lifetime, deduced defect density as well as suppressed recombination. These positive effects, combined with a heterostructure created by perovskite bulks and PQDs facilitating hole transport at the interface, enable an improvement in device efficiency from 16.71% to 17.93%. The interface issue between the carbon electrode and perovskite absorber is considered as the main barrier preventing the development of hole transport material-free carbon-based perovskite solar cells. An interlayer comprised of nano-sized perovskite quantum dots with surface capping ligands can be employed as hole extractor, defect passivator, and morphology changer, concurrently, for achieving high-performance photovoltaic devices.image & COPY; 2023 WILEY-VCH GmbH