Strategy of Enhancing Built-in Field to Promote the Application of C-TiO2/SnO2 Bilayer Electron Transport Layer in High-Efficiency Perovskite Solar Cells (24.3%)

Combining two kinds of electron transport layer (ETL) which have complementary advantages into a bilayer structure to form a bilayer ETL is an effective way to transcend inherent limitations of single-layer ETL, which is very helpful in the development of perovskite solar cells (PSCs). In this work, a strategy is proposed to break constraints on the application of the staggered bilayer ETL in high-efficiency PSC, namely utilizing a built-in field to overcome the dilemma in E-CBM making it possible to improve V-OC and FF simultaneously by tuning the Fermi level of ETLs properly. According to the strategy, a bilayer ETL structure comprised of C-TiO2 and SnO2 layer and corresponding Li-doping process are developed, and the characterization results confirm the effectiveness of the strategy, making the potentials of the C-TiO2(Li)/SnO2 bilayer ETL fully released for its application in high-efficiency PSCs: a V-OC of 1.201 V for an ordinary triple-cation-perovskite-based PSC and a photoelectric conversion efficiency of 24.3% for a low-bandgap-perovskite-based PSC with high haze FTO superstrate are successfully achieved, indicating that the C-TiO2(Li)/SnO2 bilayer ETL is a successful application paradigm of the proposed strategy and very promising in the application of high-efficiency PSCs.

Automated summary

Combining two complementary electron transport layers into a bilayer structure and utilizing a built-in field to overcome constraints can significantly improve the efficiency of perovskite solar cells. The developed C-TiO2(Li)/SnO2 bilayer ETL successfully improved V-OC and FF, achieving high photoelectric conversion efficiencies in different types of PSCs.