Highly efficient wide bandgap perovskite solar cells with tunneling junction by self-assembled 2D dielectric layer

Reducing non-radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high-performance wide-bandgap perovskite solar cells. This study proposes the self-organization of a thin two-dimensional (2D) perovskite BA₂PbBr₄ layer beneath a wide-bandgap three-dimensional (3D) perovskite Cs_0.17FA_0.83Pb(I_0.6Br_0.4)₃, forming a 2D/3D bilayer structure on a tin oxide (SnO₂) layer. This process is driven by interactions between the oxygen vacancies on the SnO₂ surface and hydrogen atoms of the n-butylammonium cation, aiding the self-assembly of the BA₂PbBr₄ 2D layer. The 2D perovskite acts as a tunneling layer between SnO₂ and the 3D perovskite, neutralizing the energy level mismatch and reducing non-radiative recombination. This results in high power conversion efficiencies of 21.54% and 19.16% for wide-bandgap perovskite solar cells with bandgaps of 1.7 and 1.8 eV, with open-circuit voltages over 1.3 V under 1-Sun illumination. Furthermore, an impressive efficiency of over 43% is achieved under indoor conditions, specifically under 200 lux white light-emitting diode light, yielding an output voltage exceeding 1 V. The device also demonstrates enhanced stability, lasting up to 1,200 hours.