Pressure Engineering to Enable Improved Stability and Performance of Metal Halide Perovskite Photovoltaics

Abstract

In this work, we demonstrate that an external pressure of 15-30 kPa can significantly improve metal halide perovskite (MHP) film thermal stability. We demonstrate this through the application of weight on top of an MHP film during thermal aging in preserving the perovskite phase and the mobile ion concentration, an effect which we hypothesize reduces the extent to which volatile species can escape from the MHP lattice. This method is shown to be effective for a more scalable approach by only applying the weight to a cover glass during the lamination of an epoxy-based resin, after which the weight is removed. The amount of pressure applied during lamination is shown to correlate with stability in both 1 sun illumination and damp heat testing. Lastly, the performance of MHP photovoltaic devices is improved using pressure during lamination, an effect which is attributed to improved interfacial contact between the MHP and the adjacent charge transport layers and healing of any voids or defects that may exist at the buried interface after processing. As such, there are implications for tuning the amount of pressure that is applied during lamination to enable the durability of MHP solar modules toward manufacturing-scale deployment.

Keywords: defects; durability; encapsulation; ion migration; lamination; perovskite solar cells; photoluminescence; reliability; stress.

Figure 1

Optical microscope images of (a) control MHP film before exposure to heat, (b–d) MHP films after exposure to heat at 85 °C, 0% humidity for 461 h (b) with no pressure on top, (c) with 15.2 kPa pressure (d) with 30.4 kPa pressure.

Figure 2

N_o vs. exposure time for MHPs tested with a pressure of either 0 kPa, 15.2 kPa, or 30.4 kPa applied on top of them while aging at 85 °C for a total period of 72 h. N_o (cm⁻³) is a density measurement, referring to the quantity of mobile ions per cubic centimeter in the material.

Figure 3

(a) Schematic of device layering during the curing process of the epoxy encapsulant, PL data with light exposure (51 h of continuous solar operation at 1000 W/m² (1 sun)) of encapsulated MHP samples under a pressure of (b) 0 kPa, (c) 15.2 kPa, and (d) 30.4 kPa. PL data with damp heat exposure (185 h of damp heating at 85 °C/85% relative humidity) of encapsulated MHP samples under a pressure of (e) 0 kPa, (f) 15.2 kPa, and (g) 30.4 kPa.