Researchers from Wuhan University, South China Normal University and Chinese Academy of Sciences (CAS) have explained that while all-perovskite tandem solar cells (TSCs) offer exceptional performance and versatile applicability, a significant challenge persists in bridging the power conversion efficiency (PCE) gap between small- and large-area (>1 cm2) devices, which presents a barrier to the commercialization of all-perovskite TSCs.
Now, the team introduced a specialized crystal-modifying agent, piracetam, tailored for wide-bandgap perovskites, homogenizing top wide-bandgap subcells and enabling the construction of efficient large-area TSCs.
Piracetam, featuring amide and pyrrolidone moieties, initially modulates perovskite nucleation, resulting in large-sized grains, preferred (110) orientation, enhanced crystallinity and uniform optoelectronic properties. During the subsequent annealing process, it further eliminates residual PbI2 and facilitates the formation of one-dimensional (Pi)PbI3 (Pi = piracetam) perovskite nanoneedles at the grain boundaries and surfaces.
Consequently, single-junction 1.77 eV-bandgap solar cells achieved a certified open-circuit voltage of 1.36 V and a PCE of 20.35%.
Furthermore, the monolithic two-terminal all-perovskite TSCs, with aperture areas of 0.07 cm2 and 1.02 cm2, yielded PCEs of 28.71% (stabilized 28.55%, certified 28.13%) and 28.20% (stabilized 28.05%, certified 27.30%), respectively, demonstrating a minimal PCE loss of 0.51% when transitioning from small-area to large-area devices.
In addition, piracetam demonstrates broad applicability across different perovskite compositions, increasing the PCE from 23.56% to 25.71% for single-junction 1.56 eV-bandgap counterparts.
This method could provide an effective pathway for scalable and efficient all-perovskite TSCs.
