Color tunable efficient semitransparent perovskite solar cell by bandgap and thickness engineering for enhancing light utilization efficiency

Abstract

Semitransparent perovskite solar cells (ST-PSCs) are considered highly promising for applications in buildingintegrated photovoltaics (BIPV) and vehicle-integrated photovoltaics (VIPV), where both efficiency and aesthetics are critical. The key challenge lies in balancing power conversion efficiency (PCE) with average visible transmittance (AVT). To be viable for BIPV, devices must typically achieve a light utilization efficiency (LUE) greater than 2.5%, where LUE is defined as the product of PCE and AVT. A common approach to achieving semitransparency is by reducing the perovskite film thickness. While this increases AVT, it usually compromises PCE, leading to a drop in LUE. To overcome this, thickness and bandgap of the perovskite can be engineered, enabling color-tunable devices that retain functionality while offering aesthetic versatility. In this work, we investigated the combined influence of bandgap and thickness on ST-PSC performance using three perovskite (FA0.85Cs0.15PbI3-xBrx, x = 0, 1, 2) composition. Thinner films, however, tend to suffer from increased surface defects. To address this, propane diammonium iodide (PDAI2) was introduced as a passivation layer, effectively suppressing surface defects and enhancing device performance. Using three perovskite compositions with distinct bandgaps, we systematically investigated the relationship between optical transparency and photovoltaic performance. Among them, the highest LUE values of 3.22% and 3.06 % were obtained for 1.56 eV and 1.95 eV STPSC, respectively. Notably, the optimized FA0.85Cs0.15PbI2Br (1.75 eV) perovskite achieved a remarkable LUE of 4.51% (corresponding to a PCE of 12.40%). Further optimization of the FA0.85Cs0.15PbI2Br perovskite thickness led to one of the highest reported LUEs of 4.92%, with a PCE of 11.9% and an AVT of 41.35% (400-800 nm), alongside a low voltage (V) deficit of 0.48 V on 1 cm2 active area.