Suppressing Ion Migration across Perovskite Grain Boundaries by Polymer Additives

Abstract

Passivation of organometal halide perovskites with polar molecules has been recently demonstrated to improve the photovoltaic device efficiency and stability. However, the mechanism is still elusive. Here, it is found that both polymers with large and small dipole moment of 3.7 D and 0.6 D have negligible defect passivation effect on the MAPbI 3 perovskite films as evidenced by photo thermal deflection spectroscopy. The photovoltaic devices with and without the polymer additives also have comparable power conversion efficiencies around 19%. However, devices with the additives have noticeable improvement in stability under continuous light irradiation. It is found that although the initial mobile ion concentrations are comparable in both devices with and without the additives, the additives can strongly suppress the ion migration during the device operation. This contributes to the significantly enhanced electrical-field stress tolerance of the perovskite solar cells (PVSCs). The PVSCs with polymer additives can operate up to −2 V reverse voltage bias which is much larger than the breakdown voltage of −0.5 V that has been commonly observed. This study provides insight into the role of additives in perovskites and the corresponding device degradation mechanism.

Origin, Influence, and Countermeasures of Defects in Perovskite Solar Cells

“…The GBs form a convenient channel for water diffusion and ion migration, which leads to the degradation of crystal grains and is the main source of devices instability. [176,177] Thereby, proper passivation of the surface and GBs to improve PCE and stability at the same time, which is of great significance for breaking through the development bottleneck of PSCs and realizing the commercial application. [178]…”

Emerging Perovskite Solar Cell Technology: Remedial Actions for the Foremost Challenges

“…has investigated the polar polymer contributions to passivate defects in MAPbI 3 perovskite and enhance the PSCs performance. [ 245 ] Two different polymers with a large difference in dipole moment were selected. The first one was a poly[4,8‐bis(5‐(2‐ethylhexyl) thiophen‐2‐yl) benzo [1,2‐b;4,5‐b′] dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno [3,4‐b]thiophene‐)‐2‐carboxylate‐ 2‐6‐diyl)] (PCE10), which has a large dipole moment of 3.7 D, and the other was a mono‐polymer polystyrene (PS) with very small dipole moment of 0.6 D. These two polymers were mixed with a proper weight ratio with perovskite material and fabricated into PSCs.…”

Perovskite/Si tandem solar cells: Fundamentals, advances, challenges, and novel applications

“…Such emerging perovskite solar cell (PVSC) is considered to be a superstar in PV field because, as shown in Figure 1, the efficiency growth rate of PVSCs is much faster than that of Si‐based PV technology. On the one hand, the metallic halide perovskite materials have superb optoelectronic properties such as high absorption coefficient, long carrier diffusion length, high carrier lifetime, and small exciton binding energy 11–13 . On the other hand, the perovskite PV technology attracts tremendous attention all over the world since the first report of perovskite‐based dye‐sensitized solar cell with device efficiency of 3.8% in 2009 14 .…”

“…On the one hand, the metallic halide perovskite materials have superb optoelectronic properties such as high absorption coefficient, long carrier diffusion length, high carrier lifetime, and small exciton binding energy. [11][12][13] On the other hand, the perovskite PV technology attracts tremendous attention all over the world since the first report of perovskite-based dye-sensitized solar cell with device efficiency of 3.8% in 2009. 14 Since then, significant efforts have been made in device structure optimization, 15,16 perovskite composition engineering, 17 perovskite crystal growth controlling, 18,19 perovskite bulk and surface defects passivation, 20 charge-transporting layer optimization, 21,22 and device interface engineering 23 to increase the device efficiency rapidly to a certified value of 25.5% within a decade of development.…”